Seed production technology of Cucurbits

INTRODUCTION

Cucurbits are vegetable crops belonging to family Cucurbitaceae, which primarily comprised species consumed as food worldwide.

The family consists of about 118 genera and 825 species. Although most of them originated in old world, many species originated in the new world and at least seven genera in both hemispheres.

There is tremendous genetic diversity within the family, and the range of adaptation for cucurbit species includes tropical and subtropical regions, arid deserts, and temperate regions. a number of cucurbit vegetables are exported from India .

Cucurbits are consumed in various forms i.e., salad (cucumber, gherkins, long melon), sweet (ash gourd, pointed gourd), pickles (gherkins), deserts (melons) and culinary purpose. Some of them e.g. bitter gourd) are well known for their unique medicinal properties.

In India, a number of major and minor cucurbits are cultivated in several commercial cropping systems and also as popular kitchen garden crops.

Cucurbits share about 5.6 % of the total vegetable production of India and according to FAO estimate, cucurbits were cultivated on about 4,290,000 ha with the productivity of 10.52 t/ha.

According to an estimate, India will need to produce 215,000 t of vegetables by 2015 to provide food and nutritional security at individual level and, being a large group of vegetable; cucurbits provide better scope to enhance overall productivity and production.

 

  Varieties of different cucurbitaceous vegetable crops.

SL.NO.	CROP	VARIETY	SOURCE
1	WATERMELON	ARKA MANIK ARKA JOTHI (F1) MADHU (F1) MILAN (F1) ASAHI YAMATO SUGAR BABY DURGAPURA MEETHA DURGAPURA KESAR IMPROVED SHIPPER	IIHR BANGALORE -DO- INDO AMERICAN HYBRID SEEDS, BANGALORE IARI, NEW DELHI IARI, NEW DELHI DURGAPYRA, RAJASTHAN -DO- PAU, LUDHIANA
2	MUSKMELON	ARKA JEET ARKA RAJHANA PUNJAB SUNHERI PUNJAB HYBRID HARA MADHU DURGAPURA MADHU DURGAPURA SELECTION 1 PUSA SHARBATI PUSA MADHURAS	IIHR, BANGALORE -DO- PAU, LUDHIANA -DO- -DO- DURGAPURA, RAJASTHAN -DO- IARI, NEW DELHI IARI, NEW DELHI
3	LONGMELON	ARKA SHEETAL	IIHR, BANGALORE
4	CUCUMBER	JAPANESE LONG GREEN PUSA SANYOG (F1) POINSETTE PRIYA (F1)	IARI, KATRAIN IARI, KATRAIN IARI KATRAIN INDO-AMERICAN HYBRID SEEDS, B’LORE
5	ROUNDMELON	ARKA TINDA	IIHR, BANGALORE
6	BOTTLEGOURD	ARKA BAHAR PUSA SUMMER PROLIFIC LONG PUSA SUMMER PROLIFIC ROUND PUSA MEGHDOOT (F1) PUSA MANJARI (F1)	IIHR,BANGALORE IARI, NEW DELHI -DO- -DO- -DO-
7	ASHGOURD	CO-1	TNAU, COIMBATORE
8	SPONGEGOURD	PUSA CHIKNI	IARI, NEW DELHI
9	RIDGEGOURD	PUSA NASDHAR	IARI, NEW DELHI
10	BITTERGOURD	ARKA HARIT COIMBATORE LONG PUSA DO MOUSAMI	IIHR, BANGALORE TNAU, COIMBATORE
11	SUMMER SQUASH	AUSTRALIAN GREEN PATTY PAN HYBRID 1 & 2	IARI, KATRAIN IIHR, BANGALORE IARI, KATRAIN
12	WINTER SQUASH / PUMPKIN	ARKA SURYAMUKHI	IIHR, BANGALORE
13	PUMPKIN	ARKA CHANDA CO 1 CO 2	IIHR, BANGALORE TNAU, COIMBATORE -DO-
14	SNAKE GOURD	CO 1	-DO-

Average fruit and seed yield per hectare.

SL NO	CROP	AVG FRUIT YIELD (Q/HA)	AVG SEED YIELD (KG/HA)
1	Cucumber	100-200	400-500
2	Bitter gourd	80-120	250-300
3	Bottle gourd	150-200	300-400
4	Ridge gourd	100-120	200-250
5	Sponge gourd	100-120	200-250
6	Round gourd	100-150	100-120
7	Watermelon	300-400	200-300
8	Muskmelon	120-150	150-200
9	Pumpkin	250-350	400-500

CLIMATIC REQUIREMENT

v  Cucurbits are warm season crops that grow best from 21⁰c to 32⁰c.

v   Freezing kills the plants & cool weather below 16⁰c slows or stops growth.

^v   Cucurbit seed germinate & emerges in as little as 4 days at a soil temperature of 25⁰c and from 6 to 12 days at 20⁰c.

^v    Most cucurbit seed do not germinate well below 16⁰c.

^v   Cucurbit seed relatively less vigorous & stand establishment is not a problem if proper soil preparation, temperature & moisture condition are met.

SOILS

ü  Fairly tolerant to acid soils.

ü  Prefers 6.0 to 7.0

ü  Sensitive to triazines.

ü  Soil temperature 55 to 60f to plant

ü  Plant 1.5cm or deeper - too deep delays emergence

GROWING CONDITIONS FOR CUCURBITS:

·         Prefer well-drained soils - loamy sands.

·         Like moderate to high organic matter.

·         Cool growing season (clouds) may cause bitter fruit.

·         Micronutrients of concern: manganese and zinc especially when the  ph is too high.

LAND REQUIREMENT

The land should be free of volunteer plants. the soil of selected fields should be well aerated.

Field inspection

A minimum of three inspections should

be made, the first before flowering, the second during flowering & fruiting stage & the third at the mature fruit stage & prior to harvesting.

Field standards

General requirement

      Isolation

Specific requirements

      Off types

      Objectionable weed plants

Isolation
When hybrid seeds are produced in the field, an isolation distance of at least 1000 m from other cucumber plants is required. in the case of foundation seed production, isolation should be at least 1500 m. these isolation requirements may be avoided when seeds are produced inside insect-proof structures (George, 1999),

Isolation distance

sl.no	crop	Minimum distance (m)
		Foundation	Certified
1	Cucumber	1000	500
2	Bitter gourd	1000	500
3	Bottle gourd	1000	500
4	Ridge gourd	1000	500
5	Sponge gourd	1000	500
6	Round gourd	1000	500
7	Watermelon	1000	500
8	Muskmelon	1000	500
9	Pumpkin	1000	500

Specific requirements

sl no	factor	Maximum permitted (%)
		Foundation	Certified
1	Off types	0.10	0.20
2	Objectionable weed plants	none	none

Preparation of land

nPrepare the field to a good tilth by one deep ploughing, two to three harrowing followed by leveling.

Seed source of seeds

      Obtain nucleus/ breeder/ foundation seed from source approved by a seed certification agency

Seed standards

sl no	factors	standards for each class
		foundation	certified
1	Pure seed (min)	98%	98%
2	Inert matter (min)	2%	2%
3	Other crop seeds (max)	5/kg	10/kg
4	Total weed seeds(max)	none	none
5	Objectionable weed seeds (max)	none	none
6	Germination (min)	60%	60%
7	Moisture (max)	7%	7%
8	For vapour proof containers (max)	6%	6%

Time of planting, spacing & seed rate requirements

of cucurbits

sl.no	crop	time of planting	spacing (cm)	seed rate (kg/ha)
1	Cucumber	1) Jan-Feb 2) June-July	120-150 x 100-120	4-5
2	Bitter gourd	1) Jan-Feb 2) June July	100-150 x 100-120	5-6
3	Bottle gourd	1) Jan-Feb 2) June July	300 x 100	6-8
4	Ridge gourd	1) Jan-march	100-50	4-5
5	Sponge gourd	1) Jan-Feb 2) June July	100-50	4-5
6	Round gourd	1)   Jan-Feb 2)   may-June	120 x 60	3-5
7	Watermelon	1)   Jan-Feb 2)   April-may	200 x 150	5-6
8	Muskmelon	1)   Jan-march 2)   April-may	200 x 100-150	4-5
9	Pumpkin	1)   Jan-Feb 2)   June-July	200 x 100-150	6-8

Planting       

There are two methods, which are generally used for sowing of cucurbits.

nPits are prepared at proper spacing by adding well rotted farmyard manure and a number of seeds are sown on each hill.

nFurrows are made at row to row spacing & seeds are sown on the edged of the furrows 60 to 90 cm apart on both sides, above the water level so that capillary movement receives the water. Two-three seeds may be sown at each place.

Requirement of manures & fertilizer in cucurbits

sl no	crop	n (kg/ha)	p (kg/ha)	k(kg/ha)	fym(t/ha)
1	cucumber	50	30	40-60	15-20
2	bitter gourd	40	30	30	20-25
3	bottle gourd	40-60	40-60	60-80	15-20
4	ridge gourd	30-50	30-40	30	10-15
5	sponge gourd	30-50	30-40	30	10-15
6	round gourd	40-50	30-40	30-40	10-15
7	watermelon	60-80	40-60	60-80	30-40
8	muskmelon	80-100	80-100	100-120	25-30
9	pumpkin	40-60	50-60	60-80	15-20

Roughing

v  Before flowering.

v  Flowering stage.

v  Fruit developing stage.

v  Maturity stage.

Plant & flower development

      Cucurbit flower buds begin to appear several nodes above the cotyledons & develop into either male (staminate) or female (pistillate) flowers.

      The first flowers produced are usually male. the plant produces many more male than female or perfect flowers to ensure an ample supply of pollen throughout the flowering period.

      Female flowers appear after the early flesh of male flowers.

       Following pollination, seed develop within the fruit of the fertilized female or perfect flowers.

Pollination in the garden

Cucurbit flowers may be perfect (have male and female parts) or imperfect (have only one or the other).

nMale flowers produced early in the season (day length >14 hrs.)

nFemale flowers begin to show up along with the males around the summer solstice and male flowers predominate in august until frost genetics, day length, and temperature determine what gender of flowers are produced

Pollination:

ü  2 to 3 hives per acre for gynoecious types.

ü  Flowers open for one day.

ü  Bee activity greatest morning to early afternoon.

ü  Wet, cool conditions reduce bee activity and causes poor fruit set.

ü  Bees placed too early go elsewhere.

ü  3 to 6 days after bloom starts - place the bees.

ü  Water within 1/4 mile.

ü  Apply insecticides late in the day or at night when there is little or no bee activity.

ü  Bees attracted to sweet corn pollen.  use caution with insecticides and sweet corn fields/honeybees.

ü  Cucumbers, melons, squash, will not cross

ü  Pollinate with each other.

ü  Cultivars (varieties) within each species will

ü  Interbreed.

ü  1 to 2 colonies per acre - general recommendation.

ü  Multiple visits of eight or more visits per flower are required.

ü  Hybrid cucumbers at high plant populations - 15 to 20 visits.

ü  Consider a written contract between beekeeper and grower (number and strength of colonies, rental fee, time of delivery, and distribution of bees in the field).

Training of vines

ü  During monsoon season, crops like cucumber, bitter gourd, ridge gourd, sponge gourd, & little gourd give far better yields when they are allowed to grow on a pandal or bower made of bamboos and sticks.

ü   Staking will help to escape fruits from direct contact with wet soil. contact with wet soil causes fruit rotting.

ü  The growth & development of fruits when they bare hanging may be better than lying on the ground surface.

ü  Generally, staking of straw or grasses on the ground before spread of vines.

ü   This will act as a good mulch and prevent direct contact of the fruit to the soil.

ü  When cucurbits are grown on raised bed or on mounds, training of vines is needed so that they grow properly without undesired criss-crossing.

ü   If needed, vines may be trimmed to optimum length.

ü  Staking in cucumber is very successful for getting higher production.

ü  it is done with bamboo sticks or tree branches

Fruit set and development

Monoecious types -

•         Set progressively at the nodes.

•         Developing fruit at the lower nodes may inhibit or delay fruit at subsequent nodes.

•         Size and shape related to number of seeds produced.

•         One or more pollen grains needed per seed.

•         Poor pollination is the main cause of fruit abortion,      misshapen fruit, or poor fruit set.  Stress may also be a      factor (soil or weather).

Crop maturation: 40 to 50 days

Seed extraction

·         Usually, fruits of bottle gourd, sponge gourd and ridge gourd are dried completely and seeds may be extracted as and when required for planting, if place for storage of fruits is available.

·         Seeds are extracted as soon as possible from the fully ripen fruits of cucumber, watermelon, muskmelon, bitter gourd and little gourd etc. fully ripen fruits of pumpkin may be

·         Fully ripen fruits of pumpkin may be kept for a couple of weeks or so and not necessary to extract seeds just after harvesting.

·         The seeds along with placental material are scooped from the fruits of cucumber, bitter gourd, muskmelon and pumpkin, because  seeds remain in central fruit cavity.

·         The seeds in the watermelon fruit, unlike most cucurbits, are distributed through the central area of the fruit pulp.

·         The extraction method depends on watermelon fruit maceration.

·         Fermentation may cause discoloration of seeds and reduction in germination potential.

·         Hydrochloric acid at a concentration of 10% may be used to accelerate fermentation in high quality seed lots (Peñaloza, 2001).

Washing

• Seeds are washed slowly with care in the running water.
• The pieces of rind, coarse material from the seeds and fine pulp are separated through screening.
• Fermentation is usually avoided on the seed extraction in almost all cucurbits because the seeds easily discolours and reduces the germination potential of the seeds.
• Off season vegetable production

• Off season vegetable production through nursery management and greenhouse cultivation has been playing an important role in increasing the profit of the farmers.
• Mulching has been very effective for hybrid crops as it moderate the soil temperatures.
• During summer and rainy seasons, straw mulch has been found effective. use the pgr has been proven to be beneficial for earliness, quality and yield in cucurbits.
• Foliar spray of ethephon (100-500 mg/l), ga (10 mg/l), mh (50 - 150 mg/l) and tiba (25-50 mg/l) increase the yield in most of the cucurbits (sonkar 2003). Staking in cucurbits has been found to be very effective in getting maximum yield and better quality of fruits (Pandey et al. 2001).
• In this regard, pruning is also beneficial and in cucumber, single stems are allowed to grow with 2-3 fruiting branches, while in melon, lateral branches are removed up to 6-9 nodes, leaving 2-3 fruiting branches.

Use of hybrids in cucurbitaceous family

Some advantages: earliness, yield, fruit quality, disease

Resistance

• Hybrids are most common in summer squash, cucumber,

Melon, and watermelon

• Adoption of hybrid cultivars favored because:

- High number of seeds per fruit

- Relatively low number of seed required for

Establishment

- Cost-efficient hybrid seed production

Techniques used for hybridization:

Hand emasculation and pollination

• Flower removal or manual removal of male flowers from the female parental line

• Gynoecy or the use of lines with only female flowers as female parent of  hybrids

• Use of growth regulators to modify sex expression

• Genetic male sterility

cucumber  Cucumis sativus

• Family cucurbitaceae
• Native to India
• Warm season, herbaceous annual.
• May be determinate or indeterminate.
• Leaves and stems are spiny.
• Leaves are triangular with rounded lobes with the middle lobe longer.
• Self-pollinated.
• cucurbitacin is what causes people to have difficulty digesting cucumbers.
• gynoecious – all female. Need ≥ 1 male plant to pollinate.
• parthenocarpic – self-fertile & doesn’t require pollination.
• Requires isolation from other fruit to avoid pollination to provide seedless fruit.

Cucumber culture

Ø  plant seeds 1-1½ inches deep and 8-12 inches apart

Ø  require soil temperatures of 60°f

Ø  trellis on strong wire mesh to save space

Harvesting & seed extraction

The seed crop is ready for harvest when the fruits have turned pale or golden. the seeds are obtained by cutting individual fruits in half, longitudinally and scraping them out with knife. At the time of extraction, the seed will not separate completely from the pulp surrounding it, fermentation, mechanical means and chemical extraction break its adherence to this material.

Parthenocarpic fruit

·         Set fruit without pollination.

·         May be hormone induced.

·         May be genetic and will not require hormone application.

·         Usually no seed.

·         For greenhouse production.

Production of cucumber hybrid seeds

• Cucumber is the species most extensively studied in the cucurbitaceae for the production of hybrid seed. the physiology of cucumber growth and productivity has been investigated as a requirement for optimizing greenhouse production (Wien, 1997).

• Additionally, understanding the genetic and hormonal control of flower sex expression has contributed to improving hybrid seed production of this species.

• Among the many types of cucumber cultivars, it is possible to find gynoecious genotypes, i.e. plants that only have female flowers. parthenocarpy, or the development of fruits without fertilization and seed formation, is another important trait available for cucumber breeding.

• gynoecious cultivars with parthenocarpic fruits are usually preferred for greenhouse production because of their higher yields and ease in crop management.

Cucumber hybrids

• Heterosis or hybrid vigor has been reported in several cucurbit species.
• Earliness, yield and fruit quality are some of the most frequent traits influenced by heterosis.
• Additionally, several disease resistance genes have been introduced in f1 hybrids.
• Today, most commercial summer squash, cucumber, melon, and watermelon cultivars are f1 hybrids (Robinson, 2000).

Gynoecious x monoecious hybrids

• Hybrids have a tendency to produce mostly female
• Flowers, however a variable amount of male flowers is still produced

• In non-parthenocarpic hybrids, blending with seed of monoecious cultivar (~10%) may be required

Gynoecious x gynoecious hybrids

• Resulting f1 hybrid is homozygous for f, i.e. more stable for gynoecy.

• Relatively more important for parthenocarpic hybrids used for greenhouse production

Use of growth regulators to promote maleness

• Ethephon is the most common growth
• Regulator used. this compound is mainly used in commercial hybrid seed production of
• Summer squash and some monoecious cucumber hybrids.
• Other growth regulators like ga3 , agno3 also used.

Cucumber diseases

• cucumber mosaic virus
• downy mildew: (pseudoperonospora cubensis)
• watermelon mosaic virus
• anthracnose (colletotrichum lagenarium)
• scab (cladosporium cucumerinum)

Melon  Cucumis melo & citrullus lanatus

• Family cucurbitaceae
• Native to Africa
• Introduced to America in 1400s.
• Warm season, herbaceous annual.
• May be determinate or indeterminate.
• Melon leaves are oval to kidney-shaped with 5-7 lobes.
• Melons can only cross-pollinate with members of the same species.

• Watermelon leaves are heart-shaped with 3-7 lobes.
• Plants are monoecious & can be self or cross pollinated.

Melon culture

• Require 90-125 days to produce a crop.
• Seed at ½ to 1 inch depth, 5 ft centers.
• Don’t transplant well.
• Chilling sensitive.
• Require warm, sunny weather to produce sweet fruit.
• Moist, well-drained soil.
• Best grown on plastic mulch.
• Bee’s essential for good fruit set.
• Only allow 1-2 fruits to develop per plant.

Method of sowing

The seeds are sown after soaking them in water overnight, in the manner similar to that described for cucumber.

Harvesting

Fruits are ready to harvest when the point of attachment with the stem shows a wide crack (full ripe stage) and the seed is practically mature. it is advisable to wait until sufficient  fruits ripen before harvesting. Fruits, after picking are placed in piles. they are cut open by hand with a knife and the seed pulp are scraped into container. later the seeds are separated from the pulp either by fermentation, followed by washing or by washing alone. The seeds after washing in water are dried quickly in the sun.

Summer squash  Cucurbita pepo

• Family cucurbitaceae
• Native to the Americas
• Warm season, frost tender, herbaceous annual.
• May be determinate or indeterminate.
• Leaves are 3-lobed or entire.
• Plants are monoecious.
• Thin-skinned, eaten when immature.
• Blossoms are edible.

Winter squash

 
Cucurbita maxima, pepo, moschata

• Family cucurbitaceae
• Native to Americas
• Warm season, herbaceous annual.
• May be determinate or indeterminate.
• Leaves are 3-lobed or entire.
• Plants are monoecious.
• Can cross pollinate with other cultivars of the same species.
• Hard rinds make them good for storage.

Pumpkins Cucurbita pepo

• Family cucurbitaceae
• Native to Americas
• Warm season, frost-tender, herbaceous annual.
• May be determinate or indeterminate.
• Leaves are 3-lobed and may be deeply indented.
• Plants are monoecious.
• Can cross pollinate with other cultivars of the same species.
• Mammoth pumpkins are related to Hubbard squash and are pinkish-orange in color.

Pumpkin culture

• Don’t plant before may 20 in southern wi and up to 2 weeks later in the north.
• Plant 1-1 ½inches deep 3-5 feet apart in the row with rows 4-6 feet apart .
• Moist soil.
• Warm season 65-75°f.
• Mulch.
• Bees essential.
• Shallow roots – irrigate.
• Hand  pollinate giant pumpkins so they set fruit early.
• Only allow 2 fruit per plant to develop.

Bitter gourd culture

Momordica charantia l.indoburma    ( china,malaya & burma) , 2n ( 22)

Selection of land for quality seed production 

The selection of land is the first and foremost task for a seed producer. The seed production plot must be selected carefully. A fertile and healthy seed plot will certainly produce quality seed. The field selected for seed production must not have been sown with bitter gourd in the previous season. This is done to avoid volunteer plants that cause admixture.

Selecting the right season for raising seed crop 

Seed is very sensitive to weather. Hence selecting the right season is necessary. Through bitter gourd can be grown through out the year, seed crop should be grown such that the seed matures in cool dry climate. this will facilitate proper ripening of fruits and reduce the pest and disease infection. Seasons are selected with this idea in mind.  in Tamil nadu the best seed crop growing seasons are aadi and Thai pattern i.e. June – July and January – February.

Preparation of main field and sowing 

After proper ploughing, at a spacing of 2.5 x 2 m distance take pits having 45 cm length, width and height. Ten days after that, apply 10 kg fym and ura 13 g, super phosphate 72 g and potash 19 g per pit. Then mix the above nutrients with soil and fill the pits and level them. Since, it is vining in nature better to erect the pandal at 2 m height or we can tie wires at a distance of one foot horizontally and connect those lines by tieing the wires vertically at same spacing. it will facilitate for better growth and yield and also easy for rouging operation.

Sowing 

            Generally, germination of bitter gourd seeds in the field is less and also delayed. This results in non uniformity in plant growth and fruit maturation. This can be over come by using pre germinated seeds.

         For pre germination, the bitter gourd seeds should be soaked in water for 24 hours. Then soaked seeds is to be mixed with double the volume of moist sand and seed should be fully covered by the sand and keep it for three days. During this period moisture of sand should be maintained. After that, the seeds with radicle emergence are to be collected and used for sowing.

       Seeds of 1.8 kg pre germinated seeds required for an acre may be sown in a pit with three seeds at equal distance. if we are using pre-germinated seeds, sow only three seeds per pit.

                                                                         

Growth regulator spray

Generally in cucurbitaceous vegetables the male and female flowers are born separately. The number of female flowers decides the fruit yield. hence, for bitter gourd, spraying of ethrel at 200 ppm for four times starting from 15 days after sowing and followed by weekly intervals (i.e. 2.0 ml of ethrel in 10 lit of water). This facilitates for higher fruit yield.

Harvesting

In bitter gourd the harvest is not as that done is field crops as once over harvest. The harvests will be done in different pickings in biitergourd. Here the first and last one or two harvests may be taken for vegetable. The fruits harvested in between these harvests are used for seed extraction.

 For seed purpose generally harvest will be done 5-7 days after the maturity of vegetables. Since, at that stage the seeds will attain its maturity. At that stage, there will be change in fruit colour to yellow at any portion of the fruit. After the harvest the fruits can be stored for one or two days for over and this will facilitate easy seed extraction. Fruits confirming the genetic purity with medium to large size fruits should alone be used for seed extraction. This selection and grading procedures will increase the yield of quality seed recovery.

Seed extraction method

• Selected fruits are to be used for seed extraction. In bitter gourd seed extraction is easy. Split opens the fruits longitudinally and collects the seeds along with pulp. Crush the pulp with hands and wash with excess quantity of water to remove the pulp. The extracted seeds are to be dried properly.
• It is easy to dry the seeds extracted by acid method and also remove the fungal growth over the seed coat, thus seeds possessing golden yellow colour and high vigour. The seed extracted by fermentation method posses poor vigour and off colour due to fungal activity.

Seed treatment 

            Prior to storage, seeds are treated with fungicide to ward off fungal pathogens. Seeds are mixed with carbendazim 4g/kg. a novel technique called halogen permeation treatment is also recommended now-a-days. Calcium oxy-chloride, commercially known as bleaching power and powdered calcium carbonate (lime stone) is mixed in equal ratio. This mixture is added to seed 5g/kg and stored.