INTRODUCTION
Problem
Cucumber (Cucumis sativus L.), a member of the cucurbitaceous family, ranks as one of the most popular cash crops and is the second most widely cultivated cucurbit after watermelon This versatile vegetable holds significant economic and dietary value, being a rich source of vitamins A and C, especially when consumed with the skin, which also provides beneficial carotenoids.
Cucumber (Cucumis sativus), a widely cultivated vegetable originating from India and Southeast Asia, exhibits various types based on fruit characteristics such as length, diameter, and skin texture This fast-growing crop has a shorter time from planting to harvest compared to many others, although harvest timing can be unpredictable due to temperature variations Historically, most cucumber cultivars were monoecious, producing staminate flowers first, but today, the majority of pickling and slicing cucumbers in the United States are gynoecious hybrids, which have a high ratio of pistillate to staminate flowers To ensure proper fruit set, gynoecious cultivars are often blended with monoecious plants, with an optimal mix of 10 to 15% monoecious individuals The rise of gynoecious hybrids and mechanical harvesting has made accurate harvest predictions crucial for effective scheduling and maximizing grower profitability.
Cucumbers typically need ample space for growth, but vertical trellising can help save space by training the vines upward For smaller areas like patios or compact gardens, gardeners can opt for dwarf, determinate, or compact cucumber varieties, which feature shorter vines and are often referred to as bush or compact types due to their reduced internode length.
Cucumbers are a widely cultivated vegetable fruit in Vietnam, grown year-round and enjoyed nationwide They are versatile, commonly used in salads, eaten fresh, or pickled With various sizes and colors available, cucumbers can be harvested multiple times throughout the year, yielding an average of nearly 17 tons per hectare.
Cucumbers are cultivated across all northern and southern provinces of Vietnam, with significant production in the Red River Delta and Mekong Delta regions Recently, there has been a notable increase in cucumber cultivation within net houses and greenhouses This article focuses on the development and growth of three cucumber varieties: Nep, Vic 19, and Vinaseed, specifically grown in net house environments.
Objective and requirements
Evaluation of growth and development of 3 cucumber varieties through 2 vegetative and reproductive stages
Evaluation of yield and quality of 3 cucumber varieties based on available factors From there, select the type of melon suitable for winter planting
Know how to design appropriate experiments, reasonable farming methods, and provide adequate nutrition for plants
Collect and analyze data relevant to the research topic
Know how to monitor the growth, development, and morphological characteristics of cucumber varieties
Identify some common pests and diseases on cucumber plants and methods to prevent them
And the ability to write scientific reports after completing the research project.
LITERATURE REVIEWS
Introduction
The Cucumis species likely originated in Africa, with the Middle East and Southern Asia serving as the initial domestication sites for melon and cucumber, respectively These regions have significantly contributed to plant improvement through the incorporation of genes from exotic sources.
Cucumber (Cucumis sativus var sativus) may have originated in Africa
Domestication of certain crops began approximately 3,000 years ago, primarily in India, which is recognized as the main center of diversity (Jeffrey, 1980; De Candolle, cited by Hedrick, 1919; Whitaker and Davis, 1962; Robinson and Decker-Walters, 1997) This process later spread to regions such as China, India, and the Near East (Vavilov, 1926 and 1951; Harlan, 1975), with further domestication occurring throughout Europe.
Cucumber was introduced to Greece and Italy by the Romans in the 2nd century BC, originating from Mesopotamia It made its way to France in the 9th century, England in the 14th century, and reached North America by the mid-16th century Additionally, the Spanish brought cucumber to Haiti in 1494, marking its westward spread.
India is rich in ancient names that reflect its cultural heritage The English term "cucumber" is derived from the Latin word "Cucumis." Similarly, the Bohemian "agyrka," German "Gurke," Greek "Aggouria," and European "gherkin" all originate from an ancient Aryan word.
Cucumis sativus var hardwickii, a wild relative of the cultivated cucumber, thrives in the Himalayan foothills and is traditionally used as a laxative by indigenous communities in Northern India This variety is both sympatric and cross-compatible with Cucumis sativus var sativus, exhibiting unique traits such as multiple fruiting and branching habits that are rare in common cucumbers As a result, C sativus var hardwickii showcases significant genetic diversity within the Cucumis sativus germplasm.
1996), and, thus, has potential for increasing genetic diversity in commercial cucumber (Staub et al., 1992b)
Genetic variation in cucumber germplasm from Southern China is believed to be unique to the region, potentially enhanced by rare immigration from Northern India through ancient Himalayan trade routes This germplasm has been isolated by surrounding mountain ranges, particularly the Himalayas Additionally, the Chinese cucumber germplasm has benefited from the historical "Silk Road," which facilitated the continuous introduction of genetic variation from India through Eastern Europe and the Middle East.
Research on Cucumis species, utilizing morphology, cross ability, and protein analysis, has clarified species relationships, a finding corroborated by nuclear DNA analysis Recent studies by Garcia-Mas et al (2004) employed ribosomal internal transcribed spacer sequences and microsatellite markers to define phylogenetic relationships among Cucumis species While their findings diverged from some earlier genetic relationships identified through isozyme and restriction fragment markers, they reinforced the distinct separation of C sativus from other Cucumis species, aligning with previous research.
The mountainous region of northern Vietnam, adjacent to Laos, is recognized as the birthplace of cucumbers due to the presence of wild cucumber species (Vavilop, 1926) In contrast, Kallo (1958) identifies China as the center of cucumber cultivation Chinese cucumber varieties have developed valuable recessive traits, including long fruit, unfertilized fruit, white spines, and a non-bitter taste (Ta Thu Cuc et al., 2000).
Cucumber (Cucumis sativus L.), a member of the Cucurbitaceae family, is an important plant species It falls under the genus Cucumis and is classified as C sativus L According to Teachenko (1967), cucumbers can be categorized into three types: common cucumbers, bisexual cucumbers, and wild cucumbers.
According to L.B Libner Nonneck (1989), Cucumis sativus L is just a shape of a cucumber, an important commercial vegetable Other plants also called cucumbers such as C flexuosus and C melo, West Indian cucumber
(Gherkin): C anguria L., round cucumber C prophetarum, Chinese white cucumber: C.melo var conomon or star cucumber: Sicyos angulatus
According to Raymond A.T Georgy (1989) Cucumbers come in a wide variety of sizes and shapes Cultivated species can be divided into four main groups:
• Cucumbers produced in the field are characterized by white or black spines
• Cucumbers are grown in greenhouses or like English cucumbers These pods have elongated, thornless fruits that can produce unisexual fruit
• Like Sik Kim originating from India, the fruit is slightly red or yellow-orange
• Cucumbers have size small fruits that are used for pickling
Cucumbers are categorized based on their intended use, primarily as sliced or pickled varieties According to Mark J Baselt (1986), pickling cucumbers should have a length/diameter (L/D) ratio of 2.8 to 3.2, which is smaller than that of slicing cucumbers, and this ratio can vary depending on planting density Additionally, cucumbers designated for pickling must be straight, round, and square in shape (Ta Thu Cuc et al., 2005).
C sativus is a morphologically variable annual herbaceous climber
Cucumbers can reach heights of up to 2 meters and lengths of 5 meters, featuring unbranched tendrils that grow as long as 30 centimeters The plant has alternate, simple leaves with 3 to 7 palmate lobes and serrated edges Its yellow flowers are 5-merous and can be either male or female The resulting fruits are hairless, cylindrical, warty, and can vary in color from yellow to green, growing up to 50 centimeters in length.
Cucumbers, originating from humid tropical regions, possess relatively weaker root systems compared to other crops like pumpkins and melons Their roots thrive in moist conditions and are sensitive to both drought and waterlogging While cucumber roots can extend up to 1 meter deep, the branching and accessory roots typically reach widths of 60-90 cm, particularly in semi-wild varieties In contrast, modern cultivated cucumber varieties exhibit shallower roots, generally growing only 15-20 cm deep The development of secondary roots begins 5-6 days post-germination, leading to initially weak seedling growth, which underscores the importance of early root development for future productivity (Ta Thu Cuc et al., 2005).
C sativus is a morphologically variable annual herbaceous climber The stems are prostrate, angular, and covered in white pubescence Stipules are absent, and the plant bears unbranched axillary tendrils up to 30cm long 10-16 (-
20) cm long petioles On the main body forming branches of level 1 and Level
2 Stem height depends on variety, environmental conditions, and care techniques
The pubescent leaves are alternately arranged on petioles measuring 10-16 cm long, with some reaching up to 20 cm These simple leaves are basally cordate and apically acute, featuring 3-7 palmate lobes The nearly orbicular, palmately-veined leaves range from 7 to 20 cm in length and width.
The growth of cucumber leaves is initially slow during the seedling stage, with both the number of leaves and actual leaf area gradually increasing This growth peaks during the fruiting period before declining in the later stages of development (Le Thi Khanh, 2009).
Grown stages
Cucurbit seeds are large and nutrient-rich, requiring adequate water for successful germination The optimal germination temperature ranges from 25 to 30 degrees Celsius, with seeds unable to germinate below 10 degrees Celsius Soil moisture plays a crucial role in this process, as the growth of dicotyledons is significantly influenced by variety, temperature, nutrients, and moisture levels During the seedling stage, rapid growth occurs, which is vital for the overall health of the plant (Ta Thu Cuc et al, 2005).
Calculated from when the plant has 2 cotyledons to 4-5 true leaves
During this growth stage, cucurbit plants exhibit slow development, characterized by small leaves, short internodes, and upright, non-branching stems These plants are particularly vulnerable to environmental conditions and have low resistance to pests and diseases To enhance their growth, it is essential to provide increased care, irrigation, and soluble fertilizers, specifically nitrogen fertilizers at concentrations of 0.2 - 0.3% Fertilization should occur 3 times at appropriate intervals, and it is crucial to implement disease prevention measures, such as spraying for powdery mildew.
This period is determined from the time the plant has 4-5 true leaves to the first flower
During this growth phase, the stem exhibits robust development, evidenced by a significant increase in the number of leaves, leaf area, stem length, and diameter compared to the seedling stage.
The continuous formation of first- and second-order branches, along with the tassel, is crucial for tree development If vine management is delayed, trees can quickly dominate the nutrient area, leading to their decline and negatively impacting growth Typically, the first flowers emerge 50 to 70 days after sowing, with variations influenced by the variety, environmental conditions, and care techniques During this critical period, all varieties require careful attention to maintain a balance between vegetative and reproductive growth (Ta Thu Cuc et al, 2005).
The period following fertilization, marked by the wilting of petals, leads to concentrated fruiting where plants exhibit robust growth During this phase, the above-ground and underground biomass, including stems, leaves, and fruits, reaches its peak Fruits are formed continuously, experiencing rapid increases in size and weight, resulting in well-balanced and aesthetically pleasing produce This stage is crucial for achieving optimal yield and high-quality fruits with a significant percentage of commercially viable produce (Ta Thu Cuc et al, 2005).
The rapid decline in the growth of stems, leaves, and fruits indicates that the tree is aging, resulting in a reduced number of fruits This leads to disproportionate and often malformed fruit growth, significantly impacting both yield and fruit quality.
Enhanced care and top dressing can effectively extend the productive lifespan of the land Following the harvest, prompt preparation for the next planting season allows for more efficient land use (Ta Thu Cuc et al., 2005).
Environmental factors
Light is essential for photosynthesis in plants and plays a crucial role in determining photoperiods, which refer to the length of day and night Photoperiods can be classified into short days (less than 11 hours), where few plants thrive, and long days (13 hours or more), which support more growth Additionally, variations in light intensity and day length significantly influence flowering and fruiting in plants For instance, the timing of light exposure is critical during different growth stages of cucumbers.
To enhance plant growth and development, artificial lighting can be used to supplement short natural light periods, while extended exposure to light significantly benefits their growth.
Optimal temperatures are crucial for the normal physiological processes in plants, as extreme high or low temperatures can lead to detrimental effects These temperature variations significantly impact individual life stages and growth processes in plants.
Cucumbers thrive in warm soil, requiring a minimum temperature of 10-18 degrees Celsius for germination, with an optimal range of 15.5-35 degrees Celsius The germination process is significantly affected by temperature, as the minimum for germination is 15.5 degrees, while the maximum tolerable temperature is 40 degrees Celsius The ideal growth temperature is around 20 degrees Celsius At lower temperatures, such as 12 degrees Celsius, cucumber plants grow rapidly, but prolonged exposure to 15 degrees Celsius can hinder growth, resulting in short internodes, small leaves, and light yellow male flowers Exposure to 5 degrees Celsius poses a freezing risk for most varieties, while high temperatures above 40 degrees Celsius cause wilting and halt growth, preventing the appearance of female flowers Most cucumber varieties require a vernalization stage at temperatures between 20-22 degrees Celsius (Ta Thu Cuc et al., 2005).
There is cell growth especially cell elongation We observe, monitor the temperature by day, week, month From there make a chart for evaluation and discussion
Plants rely on water for survival, as it constitutes 80-95% of their tissue mass Water is essential for transpiration and photosynthesis, which are vital for carbohydrate production and growth Without adequate moisture from precipitation or irrigation, plants can wilt permanently and eventually die To ensure optimal growth and quality, it is important to manage water levels and irrigation according to the soil moisture needs of the plants Providing sufficient water is crucial for healthy plant development.
Fertilizer
Plants, like humans, require food to thrive, and fertilizers supply essential nutrients that may be deficient in the soil For instance, cucumbers are a valuable food source, but without adequate nutrients from the roots, plants will fail to produce fruits, crops, and flowers It is crucial to apply the right amount of fertilizer for healthy growth and development; excessive use can lead to dehydration and even death Both under-fertilization and over-fertilization can hinder plant growth, as insufficient nutrients result in poor soil quality, while too much fertilizer increases soil salinity, ultimately slowing down growth.
Nutrients are vital for plant growth and replenishment, categorized into macronutrients and micronutrients They are primarily absorbed through root hairs and play a crucial role in tissue repair and essential processes Monitoring plants during their growth and development stages is important, and the appropriate nutrients can be supplied through fertilizers tailored to the specific needs of the plants, considering the type, timing, and quantity of fertilizer required.
Soil
Cucumber plants thrive in fertile, organic-rich soil with a pH range of 5.5 to 6.8, ideally between 6 and 6.5 They yield well in light, sandy soils that enhance fruit quality To maintain soil health, it's essential to rotate cucumber crops with water crops, such as rice.
The host cucumber plant thrives in highly fertile soil, as inadequate mineral nutrition negatively impacts its growth and development To enhance the sugar content of the fruit, proper fertilization with mineral fertilizers is essential (Ta Thu Cuc et al, 2005).
Nutritional value of cucumber
Cucumbers, belonging to the Cucurbitaceae family, are known for their mild, refreshing flavor and high water content, making them an excellent choice for hydration, especially in hot weather While often consumed as a savory food, cucumbers are technically a fruit and are also utilized in various beauty products.
Besides, cucumbers provide various nutrients but are low in calories, fat, cholesterol, and sodium Cucumber also contains a range of B vitamins, vitamin
Table 2.1 In one 142-g cup of unpared, raw, chopped cucumber contains the following nutrients:
Cucumbers are rich in vitamin K, which aids in blood clotting and may promote bone health Their fiber content helps manage cholesterol levels, potentially reducing the risk of cardiovascular issues Additionally, cucumbers offer skin health benefits; applying sliced cucumbers can cool and soothe the skin, alleviating swelling, irritation, and sunburn When placed on the eyes, they can reduce morning puffiness With their low-calorie content, cucumbers are also a popular choice for those looking to lose weight.
The situation of cucumber production and research in the world and Vietnam
Cucumbers, originally from India, are widely consumed in America and Europe, where they are commonly enjoyed fresh or in salads Asia plays a significant role in the import-export market, contributing to the largest cucumber output According to FAO statistics, global cucumber production reached an average of 91.2 million tons in 2020, with a yield of 403.562 hg/ha.
Table 2.2 Area harvested and yield and production of world and regions in 2020
Asia accounts for approximately 90% of global production, making it the continent with the largest area, yield, and productivity for cucumber cultivation This success is attributed to favorable factors such as variety, growing methods, and a subtropical climate that is ideal for cucumber growth In contrast, Oceania, despite having the lowest area and productivity, demonstrates that advanced cultivation techniques and modern machinery can lead to high yields Meanwhile, Africa, with its extensive cultivated area, suffers from the lowest yield due to a lack of access to modern equipment and techniques Detailed statistics on harvested area, production, and yield for countries like the US, India, China, Egypt, and Japan are presented in Table 2.3.
Table 2.3 Area harvested and yield and production of countries in the world in 2020 Countries Area harvested
Cucumbers, as noted by experts from various agricultural departments, are primarily consumed fresh or as processed products The main varieties include American processing and fresh market types, Dutch gherkin, greenhouse types, German Schalgurken, MidEast Beit Alpha, and Oriental trellis (burpless) types Fresh market cucumbers, typically grown in fields or greenhouses, range in length from 15 cm (U.S and Mediterranean) to 40 cm (European), with compact fruit types like Sfran being marketed in the Persian Gulf.
The "lemon" cucumber, characterized by its lemon-like shape and pale greenish-yellow skin, is a less common variety in the fresh market Breeding efforts have utilized Cucumis sativus var hardwickii, particularly PI 183967 and PI 215589, to enhance commercial cucumber yields by improving plant architecture, fruiting habits, and leaf size However, the fruit quality issues, such as bitterness, small size, and high seed content, along with a lack of disease resistance, have hindered its adoption in commercial pickling cucumber cultivars.
Breeding for increased yield in cucumbers has been a key focus of breeding programs since the 1900s, as noted by Todd C Wehner and Rakesh Kumar Significant improvements in the yield of pickling cucumbers have been achieved through disease resistance breeding and enhanced cultural practices Additionally, advancements in gynoecious sex expression, fruit color, and direct yield improvements have contributed to higher yields in cucumber cultivars Monoecious cucumber plants, such as Cucumis sativus, typically produce sufficient pollen for fruit set, which is influenced by the number of pistillate flowers The new monoecious slicing hybrid cucumber 'NC-Sunshine' features a high percentage of pistillate nodes, indicating that a pollenizer may be necessary to optimize pollination and achieve maximum early yield.
The current state of vegetable production in our country reveals several challenges, including low output and productivity, scattered farming practices, and inconsistent quality that hinder fresh export and industrial processing Domestic consumption remains low, with per capita consumption at only 60-65 kg/year The focus on productivity over quality has resulted in Vietnamese fresh vegetables being deemed unsafe for consumers Additionally, vegetable exports are minimal, accounting for only 1-2% of total output, and our competitiveness in the international market is weak Despite the diversity and abundance of our vegetables and fruits, production is not aligned with market demands, leading to poor quality and inadequate packaging The largest cucumber-growing regions are found in the northern provinces of the Red River Delta and southern areas like Ho Chi Minh City and the Mekong Delta, as well as traditional vegetable-growing areas in the midlands and mountainous provinces, such as Da Lat and Lam Dong.
To address existing limitations, provinces such as Hai Phong, Bac Giang, Hanoi, Da Lat, and Can Tho have adopted VietGap standards for baby cucumber cultivation According to the agricultural extension center, this model demonstrates high economic efficiency with a short growing period of 100-120 days, yielding an expected 25-30 tons per hectare and a net profit of 130 million dong per hectare This initiative not only enhances farmers' livelihoods but also promotes modernization in agricultural production while ensuring product quality and safety.
MATERIALS, AND METHODS
Materials
Three different cucumber varieties, Nep, VIC 19, and Vinaseed, were used for the experiments
3.1.2 Location and time of the research project
- Research location: The study was carried out in net house No 6 of Faculty of Agronomy, Vietnam National University of Agriculture
- The project was carried out from October 18, 2021, to February 13,
- Evaluation of the growth and development of 3 cucumber varieties
- Comparison of taste characteristics of 3 varieties of cucumber
- Evaluation of common pests and diseases on cucumbers in winter.
Methodology
The experiment utilized a randomized complete block design (RCBD) conducted in a net house, featuring 6 replications Plants were cultivated in six garden beds, each measuring 1m x 2m, with two rows containing five plants per row The rows were spaced 55cm apart, and seeds were sown at intervals of 30-40 cm, positioned 20 cm from the border.
- Use a sickle to clean the surface of the soil
- Use a hoe to dig up the soil to make the soil loose
- Spread 5kg of organic microbiological fertilizer on the soil surface of each experimental plot with an area of 2m 2
To ensure optimal soil health, mix the soil with manure and moisten it with water, regularly checking the moisture levels It's crucial to maintain a balance, as the soil should neither be too dry nor overly wet.
- Cover a layer of plastic on the ground to keep the soil moist b Select seeds:
- Choose healthy, strong seeds sow about 1-2 cm in the ground
- The distance between seeds was 20cm from the edge, the distance between the two seeds was 30-40cm, the distance between the two rows was 55cm c Sow seed:
- Sow seeds 1-2 cm below the soil layer
- Provide enough water to keep moisture for seeds to germinate and then become plants that develop and grow, flower, and produce fruit d Make a trellis for cucumbers
To prevent damage to seedlings and vines, trellises were installed early after tendrils emerged This A-shaped trellising not only supports the plants but also safeguards the fruit from potential harm caused by contact with the moist ground Additionally, fertilizer was applied to promote healthy growth.
In accordance with Vinaseed and Vietgap standards, I have identified appropriate fertilizers for three cucumber varieties tested in a net house, adhering to organic farming principles to ensure safety.
Table 3.1 Amount of fertilizer and method of application for 1 ha
Song Gianh microbiological fertilizer(kg)
Potassium chloride (kali clorua) (kg)
Watering miles (7 days after planting)
Topdressing at the growth stage (20 days after planting)
Topdressing at the fruiting stage
Topdressing at the fruiting stage (40 days after planting)
Data collection
The evaluation of cucumber varieties in this study adhered to the National Technical Regulation on Testing for the Value of Cultivation and Use of Cucumber Varieties (QCVN 01-87:2012/BNNPTNT), focusing on various stages of growth.
Table 3.2 Time of growth and development stages of 3 types of cucumbers
No Stages of growth Note
2 Time of true leaves (days)
3 Time to flower first female (days)
4 Time to first fruit (days)
5 Time of first fruit collection (days) b Morphology of cucumber:
All indicators are measured 1 week/ 1 time
- Plant height: Measure from the ground until the plant is 150 cm tall
- Number of leaves: Calculate the sum from true leaves to the height of the plant 150 cm
- Leaf length: was determined based on the sum of the number of pixels between the leaf tip and petiole insertion
- Leaf width: was calculated based on the sum of the number of pixels for the widest region of the leaf
- Stem diameter: Measure around the stem with a tape measure and use the formula for the area of a circle to find its diameter
To determine the ratio of male to female flowers on a plant, first count the number of each type of flower simultaneously This count will allow you to calculate the proportion of male to female flowers effectively.
- Number of fruits: Count the number of fruits on the plant until the tree is old
- Fruit size: measure the length, diameter of the fruit
- Fruit weight: Use an electronic watch scale to measure the weight of the fruit c Sensory evaluation
- Fruit size: including fruit length and diameter fruit Take the average value of all the results Unit is cm
- Fruit color: the fruit has green, green-yellow, or green white
- Taste: sweet or not, fresh or not fresh, smelling or odorless
- Fruit cortex: thin, thick, crispy, or hard
- Thorn color: white or black
Cucumber disease
Cucumber is susceptible to various diseases such as mosaic, wilt, anthracnose, seedling blight, leaf spot, root rot, downy and powdery mildew They are some common diseases in cucumber plants
Disease severity is assessed based on the percentage of infected leaves to evaluate in 5 levels:
Level 2: disease from 10 to 25%, symbol: ++
Data analysis
The data were analyzed with Microsoft Excel – ANOVA Single Factor tool
PART IV RESULTS AND DISCUSSION
Variation in climatic conditions during the experiment
Weather plays a crucial role in agricultural production, serving as a fundamental condition for achieving high and stable yields However, fluctuations in climatic factors such as temperature, daylight duration, rainfall, and humidity significantly impact the growth, development, and yield of cucumber plants.
Cucumbers undergo a life cycle consisting of several key stages, including germination, growth in height and leaf count, flowering, and fruiting Each of these stages requires specific climatic conditions to thrive, highlighting the significant impact of weather on cucumber growth and development.
Temperature and lighting duration significantly influence cucumber growth As a light-loving plant, cucumbers thrive in warm conditions with ample light Inadequate temperature and insufficient light can lead to slow growth, increased vulnerability to pests and diseases, and reduced flowering Conversely, optimal warmth and extended light exposure promote healthy growth and development in cucumbers.
For example, tall trees, green leaves, large stems, or many flowers, are easily pollinated by insects It makes production economically efficient
Monitoring of 2 indicators on temperature and lighting time of the research project from October 2021 to February 2022 The results of the follow- up are shown in table 4.1:
Table 4.1 Temperature and lighting time affect the growth and development of 3 cucumber varieties
The data indicates that the optimal sowing and germination conditions for cucumbers occurred with an average temperature of 22 degrees and 7-8 hours of sunshine from October to November, promoting favorable growth However, by December, the temperature decreased to 18 degrees while sunshine remained at 7 hours, which may slow down cucumber development In January, the reduction in sunlight to just 5 hours, combined with a stable temperature of 18 degrees, negatively impacted growth and flowering, resulting in lower productivity By February, the temperature further dropped to 15 degrees with minimal sunlight, severely hindering photosynthesis, weakening the plants, and making them susceptible to powdery mildew, ultimately leading to plant death.
Time of growth and development stages of 3 cucumber varieties
The plant life cycle begins with seed sowing and concludes with fruit harvest External factors and cultivation methods significantly influence the growth and development of plants.
Cucumbers, like all plants, undergo distinct growth and development stages from germination to flowering, fruiting, and harvesting This process is influenced by various environmental factors, care techniques, and the genetics of the specific breed Each growth stage has unique nutrient requirements and external conditions that necessitate different care methods Cucumbers cultivated in greenhouses experience fewer external threats, such as wind and rain, which can adversely affect germination, leafing, flowering, and fruiting.
Table 4.2 Growth and development period of 3 types of cucumbers through each stage
Time of true leaves (days)
Time to flower first female (days)
Time to first fruit (days)
Time of first fruit collection (days)
Germination True leaves Flower first female
First fruit First fruit collection
Figure 4.1 Growth and development stages of cucumber
Time of true leaves (days)
Time to flower first female (days)
Time to first fruit (days)
Time of first fruit collection (days)
Days Figure 4.2 Growth and development period of 3 types of cucumber through each stage
Figure 4.2 Growth and development period of types of cucumber through stage
Table 4.2 indicates that at the germination stage, Nep germinated one day earlier than Vic 19 and Vinaseed, sprouting on day 7 after sowing, while the latter two took 8 days The seeds were directly sown into the ground without prior soaking or incubation During this stage, the plants develop roots and stems, utilizing the nutrients in the seeds, along with favorable environmental conditions in a greenhouse, which promotes rapid growth.
About 5 days after germination, the plant began to appear true leaves Nep had true leaves on the 12DAS, and Vic 19 and Vinaseed had true leaves until the 14 DAS This proves that the plant begins the vegetative process Plants will use leaves for photosynthesis, which is the main source of food for the plant Besides, the plant will combine with the roots to take nutrients in the soil to go up the stem and leaves It will help plants grow and develop faster
In the initial female flowering stage, significant differences among varieties were observed, with Vic 19 and Nep both producing their first female flower at 37 days after sowing (DAS), while Vinaseed lagged behind at 44 DAS, a delay of 7 days To support flowering, we applied top-dressings of potassium, NPK, and microbiological fertilizers, which are essential for enhancing pollination success and fruit development.
In the first fruiting stage, Nep had the first fruit really to be harvested at
At 43 days after sowing (DAS), flowering and pollination occurred within three days of flower blossom, with sunshine lasting 7-8 hours and daytime temperatures reaching 25 degrees Celsius While pollination happened simultaneously, fruit formation in Vic 19 took two days longer compared to Nep, and it took approximately eight days for fruit to mature in Vinaseed.
During the fruiting stage, a gradual decrease in temperature and sunshine hours was observed, accompanied by extended periods of cold and rain Environmental factors, along with the choice of varieties and farming methods, significantly impact the timing of each growth stage This experiment aims to evaluate and select cucumber varieties that demonstrate robust growth, high yields, and economic benefits, ultimately providing recommendations for farmers to enhance their crop production and improve their livelihoods.
Variation in plant height
Cucumber growth and development can be primarily assessed through plant height, which visibly changes over time This growth process is influenced by various factors, including temperature, rainfall, sunlight, humidity, and fertilizer application During the stage when true leaves are forming, the plant concentrates on developing its stem and leaves However, once the fruiting stage begins, the focus shifts to fruit development, resulting in less emphasis on further leaf and stem growth.
According to Ta Thu Cuc et al, 2005, Cucumber plant height is divided into 3 groups:
Group 1: trees with a height of 0.6-1m, it is called dwarf trees
Group 2: trees from 1-1.5m high, it is called the medium tree
Group 3: the tree is more than 1.5m tall, then it is called a tall tree
We observe the change in plant height shown in Table 4.3:
Table 4.3 Growth in plant height of 3 cucumber varieties (Unit cm)
44 DAS 51DAS 58DAS 65DAS 72DAS G1-Vic
24 DSN 30 DAS 37 DAS 44 DAS 51 DAS 58 DAS 65 DAS 72 DAS
Growth in plant height of 3 cucumber varieties.
Fig 4.3 Growth in plant height of 3 cucumber varieties
Table 4.3 illustrates the daily variations in plant height after sowing, revealing that the Nep variety exhibited the most significant growth and development, followed by Vic 19 in second place, while Vinaseed showed the least growth.
At 24 days after sowing (DAS), Nep exhibited the highest growth, reaching a height of 23.78 cm, which is 11.7 cm taller than Vic 19 and 13.18 cm taller than Vinaseed Vinaseed recorded the lowest height at 10.6 cm, while Vic 19 measured 12.08 cm, making it 1.48 cm taller than Vinaseed.
Between 24 and 30 days after sowing (DAS), both Vic 19 and Vinaseed reached a height of approximately 19 cm, while Nep significantly outperformed them at 47.2 cm, indicating it was twice as tall This period likely saw poor root development, resulting in weak nutrient transport from the soil to the stems and leaves, which hindered plant growth By 37 DAS, Nep's height surged to 70.17 cm, while Vic 19 experienced a growth of 29.25 cm, increasing from 19.88 cm to 49.13 cm.
At 44-51 DAS, Vic 19 increased from 61,27 to 98,08 and Vinaseed is also from 52,12 to 85,83cm Nep has a rapid growth rate, increased from 85,88 to 129,52cm (increased by 43,64 cm) At this stage, the plant is fertilized with all kinds of fertilizers Besides, now the roots are old and stronger So plants absorb nutrients from the soil to the stem and from the leaves to the roots stronger and more Up to 58 DAS, the three varieties were still growing at a slower rate because at this stage the trees started to bear fruit Trees need nutrients to grow fruit, so it will limit other factors including tree height
After 58 to 72 DAS, the plants no longer grow We can see that the Vic 19 doesn't grow anymore The Nep variety only grew from 142,33 to 144 cm As for the Vinaseed variety, it increased by 5cm, from 90,3 to 95,67cm As we all know the growth and development of plants are affected by environmental conditions, cultivation, and care Although this time the tree is still fully fertilized and well taken care of, the tree still grows poorly due to the sharp drop in temperature, cold weather, and rain.
Variation in leaf sizes
Leaves play a crucial role in plants by facilitating photosynthesis, gas exchange, and respiration, which are essential for synthesizing organic matter and producing nutrients The size of leaves, including their length and width, is vital for enhancing their functions and increasing nutrient synthesis to support the plant's overall processes Additionally, leaves are responsible for transpiration, helping to regulate the plant's temperature Leaf characteristics and lifespan are influenced by the plant's genetic variety, while their dimensions can vary based on environmental conditions and care techniques Monitoring results are detailed in Tables 4.4, 4.5, and 4.6.
Table 4.4 Growth in leaf number of 3 cucumber varieties
44 DAS 51DAS 58DAS 65DAS 72DAS G1-Vic
At 24 days after sowing (DAS), both Vic 19 and Vinaseed exhibited the same leaf count of 2.67, while Nep had a higher count of 3.5 leaves By 37 DAS, Nep continued to lead in growth with 6.17 leaves, an increase from its previous count, while Vinaseed had the lowest at 4.84 leaves Vic 19 showed significant improvement, rising from 2.26 to 5.67 leaves.
At 44-51 DAS, Vinaseed has rapid growth, increasing from 6,17 to 9,67 leaves (increasing by 3,5 leaves) Nep increased from 5,67 to 8,5 leaves The rapid growth of leaves at 24-51 DAS is because during this time the plant only focuses on developing stem, leaves, and tendrils And leaves play an important role in the development and growth of the plant
At 51-58 DAS, Vinaseed varieties developed normally, the number of leaves still increased slightly, that is increased from 7,83 to 8 leaves For Vic 19, it's reduced from 8,5 to 8 Nep doesn't increase the number of leaves but is still at 9,68
At 65-72 DAS, Vinaseed has the same number of leaves, only 8,83 leaves Vic 19 has a change from 8,83 to 9,17 leaves Nep increased from 11 to 12,67 leaves
During the two stages of growth, the number of leaves may either increase slightly or remain unchanged due to two main factors: the tree's focus on fruiting and unfavorable weather conditions, such as reduced temperatures, rain, and lack of sunlight These conditions lower the metabolism and respiration rates of the leaves, hindering photosynthesis and consequently affecting the overall growth and height of the plants Additionally, the decrease in leaf count can be attributed to the natural aging of older leaves at the base, as well as the impact of diseases that lead to leaf drop.
Besides the number of leaves, the leaf length also shows the vegetative change of the plant
Table 4.5 Growth in leaf length of 3 cucumber varieties
Seed 37 DAS 44 DAS 51DAS 58DAS 65DAS 72DAS
At 37 DAS, Vic 19 and Vinaseed were similar in leaf length which was around 10cm The leaf length of Vic 19 was 10,97cm and Vinaseed was 10,76 cm The Nep variety had the longest leaf length of 11,31 cm
At 44-51 DAS, Vic 19 increased from 12,82 to 15,69 cm Vinaseed also increased from 13,26 to 15,17 cm With Nep increased 5 cm, increased from 15,08 to 20,39 cm
At 51-58 DAS, Vic 19 had a chance, it decreased from 15,69 to 15,37 cm Vinaseed again increased from 15,17 to 15,86 cm Nep had an increase, from 20,39 to 20,66 cm
At 65-72 DAS, Vic 19 increased from 15,12 to 15,42cm Vinaseed increased from 15,88 to 16,18 cm And Nep also increased from 20,92 to 21 cm
Table 4.6 Growth in leaf width of 3 cucumber varieties
Seed 37 DAS 44 DAS 51DAS 58DAS 65DAS 72DAS
Table 4.6 illustrates the changes in leaf width among different varieties At 37 days after sowing (DAS), Vic 19 recorded a leaf width of 11.6 cm, while Vinaseed had the smallest at 10.82 cm, and Nep exhibited the longest at 11.62 cm By 44-58 DAS, Vic 19's leaf width increased from 14.4 cm to 17.84 cm, a rise of 3.44 cm, while Vinaseed's width grew from 13.74 cm to 17.03 cm At this stage, Vic 19 and Vinaseed had comparable leaf widths In contrast, Nep demonstrated rapid growth, with its leaf width expanding by 4.5 cm, from 15.31 cm to 19.91 cm.
At 65-72 DAS, all three varieties continued to increase leaf width but the speed of change was not as fast as it was earlier While Vic 19 had a small increase of 1,64 cm and an increase from 16,74 to 18,37 cm, Vinaseed reached the maximum leaf width at 65 DAS with a leaf width of 18,19cm After that, the leaf length increased from 18,19 to 18,42 cm at 72 DAS Nep still increased, with leaf width increased from 21,39 to 21,87 cm.
The change in internode length of 3 types of cucumber
The internode length serves as a key indicator of plant development and growth, with longer internodes correlating to taller plants Conversely, short and small tree trunks suggest weak growth or that the plant is still in its early stages, not yet reaching robust growth Changes in internode length are detailed in Table 4.7.
Table 4.7 Growth in internode length of 3 cucumber varieties
Seed 37 DAS 44 DAS 51DAS 58DAS 65DAS 72DAS
At 37 days after sowing (DAS), Vic 19 exhibited an internode length of 9.58 cm, while Vinaseed had the shortest at 7.17 cm, and Nep recorded the longest at 12.5 cm, indicating that the internode lengths were still short and underdeveloped By 51 DAS, internode lengths reached their maximum development, with Vic 19 increasing to 12.1 cm, marking the highest growth of 2.52 cm during flowering and the onset of fruiting Vinaseed also showed growth, rising from 7.17 cm to 7.98 cm, whereas Nep's growth was slower, increasing from 12.5 cm to 12.9 cm Between 58 and 65 DAS, Vic 19's internode length slightly increased from 12.48 cm to 12.58 cm, while Vinaseed experienced a rapid growth from 8.78 cm to 10.33 cm, and Nep grew from 12.97 cm to 13.25 cm.
Variation in stem diameter of 3 types of cucumber
The stem is a crucial organ of the plant, providing support for other parts and facilitating the transport of nutrients between the roots and leaves A robust stem helps maintain the plant's upright position, and a larger stem diameter is indicative of a healthier, more vigorous plant Changes in stem diameter are detailed in Table 4.8.
Table 4.8 Growth in stem diameter of 3 cucumber varieties
Seed 44 DAS 51DAS 58DAS 65DAS 72DAS
The stem diameters of the three varieties, as shown in Table 4.8, range from 0.4 to 0.5 cm, indicating an average size At 44 days after sowing (DAS), Vic 19 recorded a stem diameter of 0.455 cm, Vinaseed at 0.423 cm, and Nep at 0.427 cm By 58 DAS, Vic 19's diameter increased to 0.525 cm, while Vinaseed and Nep grew to 0.442 cm and 0.457 cm, respectively By 72 DAS, the growth continued, with Vic 19 reaching 0.572 cm, Vinaseed at 0.482 cm, and Nep at 0.465 cm, demonstrating a gradual increase in stem diameter across all varieties.
The change in the number of the male flowers and female flowers of 3 types
High-yielding plants rely on flowering for successful fruit formation and production, with a direct correlation between the number of flowers and the fruit set rate Insufficient flowering leads to lower yield rates Factors such as temperature, light duration, and humidity significantly influence flower appearance Monitoring reveals that the Vic 19 and Vinaseed varieties have a lower percentage of male flowers compared to female flowers, while the Nep variety exhibits a higher number of male flowers than female flowers, as detailed in tables 4.9 and 4.10.
Table 4.9 Growth in the number of male flowers of 3 cucumber varieties
Seed 37 DAS 44 DAS 51DAS 58DAS 65DAS 72DAS
Figure 4.4 Female flower of Vinaseed and Nep
Table 4.9 indicates that the Nep variety has the highest abundance of male flowers, while Vic 19 shows the least At 37 days after sowing (DAS), male flowers were exclusively present in the Nep variety, with Vic 19 and Vinaseed showing none By 44-51 DAS, all three varieties exhibited male flowers, with Nep continuing to lead in quantity The male flower count for Nep rose from 4.5 at 44 DAS to 6.17 at 51 DAS, while Vinaseed increased from 0.67 to 2 In contrast, Vic 19's male flower count decreased from 0.67 to 0.17 Ultimately, at 51 DAS, the maximum number of male flowers was observed in the Nep and Vinaseed varieties, with Vic 19 reaching its peak earlier.
44 DAS These were the 2 periods when the number of flowers was highest At
At 58 days after sowing (DAS), there was a significant decline in the number of male flowers, with Nep showing a reduction to 3.83 flowers, nearly a 50% decrease Similarly, Vinaseed's male flower count dropped to just 1 flower, also down 50% from 51 DAS By the period of 61 to 72 DAS, the number of male flowers had decreased to zero.
Table 4.10 Growth in the number of female flowers of 3 cucumber varieties
Seed 37 DAS 44 DAS 51DAS 58DAS 65DAS 72DAS
According to data from table 4.10, Vic 19 exhibited the highest count of female flowers, whereas Vinaseed and Nep showed similar quantities At 37 days after sowing (DAS), all three varieties had a low number of female flowers Notably, Vic 19 experienced an increase in female flowers from 1.17 at 37 DAS.
By 51 days after sowing (DAS), the maximum number of female flowers reached 2.56, although the overall number of flowers gradually decreased while remaining substantial As illustrated in Figure 4.5, the continuous blooming of female flowers led to the ongoing formation of fruits To ensure optimal growth and nutrient supply for the cucumbers, it is crucial to monitor and apply the right amount of fertilizer Insufficient or excessive fertilization can impair plant function, reduce fruit yield, or even result in plant death.
For the Vinaseed variety, the maximum flower count reaches 0.67 at 37 days after sowing (DAS), while it stabilizes at 0.5 flowers from 44 to 51 DAS, indicating a consistent level during the flowering and fruiting stages Excessive flower production could lead to nutrient deficiencies for both flowers and fruit, while minimizing flower count may hinder the development of subsequent fruits after the initial harvest.
At 37 days after sowing (DAS), Nep exhibited an average of 0.33 female flowers The peak was observed at 44 DAS, with the count rising to 0.85 female flowers Following this maximum, the number of female flowers gradually declined to 0.5 and remained stable in the subsequent growth stages.
At 65-72 DAS, the number of female flowers did not appear in all 3 varieties Because at this point, the temperature drops below 20 degrees Celsius
The highest temperature recorded was 20 degrees Celsius, while the lowest dropped to 8 degrees Celsius over a span of three weeks This period was characterized by rainy weather, which led to a lack of daylight.
The timing of female flower appearance in Ta Thu Cuc is influenced by several factors, including temperature, light duration, nutrient availability, and CO2 concentration Optimal conditions include a temperature range of 12 to 24 degrees Celsius, a lighting period of 10 to 11 hours per day, sufficient CO2 levels, and proper nutrition.
Cucumber plants feature two types of unisexual flowers: male and female The male flowers, which are yellow and measure 2-3 cm in diameter, grow in clusters at the leaf axils, while the female flowers are single and have shorter, thicker stalks adorned with white spikes The female flowers are noticeably fatter than their male counterparts, and their stalks are closely positioned on the plant.
Figure 4 5 types of female flowers of 3 cucumber varieties.
Pollination process for 3 types of cucumbers
Cucumber flowers primarily rely on insect pollination, although bisexual flowers can self-pollinate In net houses, the limited presence of insects necessitates human intervention for pollination Optimal conditions for flowering occur when temperatures exceed 20 degrees Celsius and daylight lasts 6-8 hours, resulting in a flowering period of 3-4 days Successful fertilization under these conditions leads to fruit development Conversely, when temperatures drop below 20 degrees Celsius and daylight is less than 5 hours, the pollination process extends to 5-7 days, resulting in a lower fruit set rate due to inadequate temperature, insufficient sunlight, and slower pistil opening, which limits both human and insect pollination opportunities.
Besides natural pollination by insects, we need to pollinate it artificially That is using hands to pollinate cucumbers Steps to pollinate flowers for cucumbers by hand are as follows:
Step 1: The best time of day pollination is 8-10 am
Step 2: Choose 1 male flower, remove 5 petals gently
Step 3: Select the female flowers that have opened the stigma
Step 4: Use your hand to put the male flower on the female pistil, rotate the male flower gently, it helps the male pollen fall into the ovary of the female flower
Due to the small number of male flowers of Vic 19 and Vinaseed, I used Nep's male flowers to pollinate all 3 types of cucumbers
Fig 4.6 Pollinating cucumbers by hand and insects.
The process of fruit formation of cucumber
Fruit plays a crucial role in the successful development and growth of cucumber plants, serving as a key indicator of economic viability based on attributes like size, shape, volume, and taste The characteristics of cucumbers, including their shape, color, and volume, vary by type, variety, and environmental conditions, as well as cultivation and care methods Typically, cucumbers are elongated and have a three-pack structure with seeds attached to the ovule Most varieties exhibit a green or yellow-green color, and upon ripening, the fruit often loses its spines or develops small spines.
The diameter of fruit is a crucial factor in determining its quality and value R.L Lower and M.D Edwards (1986) highlight that the yield of canned cucumbers is evaluated based on weight and fruit diameter While classifications and sizes of fruits vary across countries, fruit diameter can be categorized into several types.
S3 D = 1 ẵ in to 2 in 3 – 5 USD/Cwt
Note: 1 Cwt = 45,359kg; 1in = 2,54 cm
Figure 4.7 Three types of standard fruit of 3 different varieties
Figure 4.7 displays three cucumber varieties, each differing in color, shape, and size The Vic 19 variety averages 144.2 grams in weight, 14.7 cm in length, and 4.3 cm in diameter Vinaseed has an average weight of 172.7 grams, a length of 16.8 cm, and a diameter of 4.6 cm Meanwhile, the Nep variety averages 173.5 grams in weight, 18.7 cm in length, and 4.4 cm in diameter Based on the diameters of R.L Lower and M.D Edwards, all three cucumber types are classified as S3.
During the fruiting process, environmental factors and fertilizers can lead to the formation of defective fruits, as illustrated in Figure 4 These defective fruits are unsuitable for commercial production and should be removed while they are still small This practice helps minimize nutrient loss and growth time, allowing the remaining healthy fruits on the same tree to thrive.
Below is a summary table of sensory evaluation of 3 types of cucumbers shown in Table 4.11:
Fruit length 14,7 cm 16,8 cm 18,7 cm
Fruit diameter 4,3 cm 4,6cm 4,4 cm
Fruit color Green-white Green-yellow Green-yellow Fruit cortex Crispy, thin Crispy, thick Crispy, medium
Thorn color Whiter Black Black
Taste Odorless, pale taste, fresh sweet-smelling, fresh
The Nep cucumber variety stands out with the highest average fruit weight and the longest fruit length, as indicated in Table 4.11 In contrast, the Vic variety exhibits the lowest mean diameter, along with average weight and length among the three cucumber types.
Cucumbers come in three varieties, all characterized by their thick, soft, and white flesh, offering a sweet and fresh taste When harvested, these cucumbers are green and thorny, making them easily identifiable.
From the above table, some would predict that Vinaseed and Nep were with higher productivity than Vic 19 However, that was possibly incorrect Vic
The variety 19 exhibited the highest number of female flowers; however, unfavorable weather conditions during the fruit formation stage prevented successful fruit development This unfortunate situation hindered the collection of reliable data to assess the productivity of the three varieties Environmental factors, including a drop in temperature below the survival threshold for cucumber plants and a complete lack of light, contributed to the failure of fruit development and flower appearance We anticipate that further studies in upcoming seasons will help us reach a conclusive understanding of these issues.
Common diseases of cucumber plants
In Vietnam, cucumbers face numerous pests and diseases that significantly diminish productivity and farmer income The subtropical climate fosters the proliferation of these threats, making it essential to cultivate cucumbers in net houses or greenhouses to mitigate exposure to insects, pests, and adverse weather This method allows for the production of diverse cucumber varieties in various shapes, sizes, and colors while ensuring consumer safety through reduced pesticide use Ultimately, this approach aims to satisfy the increasing consumer demand for fresh, pickled, and export-quality cucumbers.
Cucumber plants are susceptible to several diseases, including powdery mildew, late blight, and virus mosaic, as well as pests like gray worms, fruit borers, spider mites, and thrips However, during the experiment, only powdery mildew was observed affecting all three types of cucumbers.
Downy mildew, caused by the oomycete pathogen Pseudoperonospora cubensis, is a significant foliar disease affecting cucumbers Symptoms include small, water-soaked lesions on the underside of leaves, which are often angular and bordered by leaf veins, eventually leading to chlorosis and necrosis Heavy sporulation occurs within these lesions on the abaxial leaf surface This disease has been reported in over 80 countries across 20 genera, impacting 50 species of the Cucurbitaceae family and resulting in substantial economic losses Downy mildew can drastically reduce yields due to its short latent period, high frequency of secondary infections, rapid spread, and year-round presence in certain cucurbit production regions.
Powdery mildew disease in stem Powdery mildew disease in leaf
Fig 4.9 Powdery mildew disease in cucumber
In Figure 4.9 We can see powdery mildew appearing at the seedling stage on the stem and then appearing on the leaves
Powdery mildew was observed between 30 to 37 days after sowing, affecting only a few leaves on some plants For instance, in a plant with 7 leaves, the ratio of infected leaves was 2 out of 7, indicating a 10% infection rate among the total plants in the experiment At this stage, only one tree showed stem infection, as illustrated in Figure 4.9 The implementation of biological control methods and the application of Daconil 75 WP, along with extended daylight hours, successfully eliminated the disease.
In early February, a significant drop in temperature, accompanied by cold, rainy conditions and high humidity, led to a rapid spread of disease among plants Within two weeks, all plants were affected, as illustrated in Figure 4.9 Consequently, the plants' growth and development were halted, with leaves losing chlorophyll and becoming incapable of photosynthesis, ultimately resulting in plant death.
Also, we can control chemistry
According to the recommendations of FAO, some drugs can be used with trade names as follows:
And preventive measures when the disease appears are:
- Sanitize the field, carry the diseased leaves to destroy far away from the planting place
- The stump is raised high, the beds are also raised high to drain water in the field for the purpose of reducing humidity to limit disease development
- Planting density should be reasonable, should not be planted too thickly, the disease will easily spread
- After harvesting, people need to clean up the garden and improve the soil to eliminate pathogens
Choose good, healthy varieties with disease resistance.