|
Genetic attributes for Seed production in Cucurbits
Cucurbits in Indian context
Cucurbits forms an important group of vegetable crops grown extensively in the country. More than 20 types of cucurbits are known, which are grown in different part of the country being variable consumer preferences. This group consists of a wide range of vegetables, either used as salad (cucumber) or for cooking (all gourds) or candied or preserved (ash gourd). The area under cucumbits cultivation is 0.42 million ha with the forecasted production of 4.5 million tonnes (FAO;2000). The persual of figures given in table revealed that average productivity (kg/ha) of cucumbits is lower than the world average in most of the crops and far below the productivity achieved by the developed countries.
Area, production and productivity of cucurbits in India during 2000
| Crop | Area (1000 Ha) | Production (1000Mt) | Productivity (Kg/ha) | highest |
| India | World |
| Pumpkin, Squash & Gourds | 355 F | 3400 F | 9577 | 12570 | 73,333 (Netherland) |
| Cucumber & Gherkins | 18 F | 209 F | 11750 | 17021 | 664286 (Netherland) |
| Watermelon | 19 F | 250 F | 13158 | 21830 | 33633 (Japan) |
| Cantaloupes & Melons | 31 F | 641 F | 20447 | 16847 | 23629 (USA) |
| F = Forecast |
The basic reasons attributed to low productivity are limited availability of quality seed, lack of production technology and environmental factors like high temperature and long photoperiod. Since, seed is a basic input, therefore the effect of application of other inputs like fertilizer, irrigation for increasing yield and productivity is also depend upon the quality of seed. It is an impartive to mentioned that standardization of seed production practices of vegetable crops have given poor attention in seedtechnology research among all India Coordinated Research Improvement Programme(AICVIP) and limited experiments were begin during 1990.
Botany
Cucurbits belongs to family cucurbitaceae which is moderately large comparising about 117 genera and 285 species distributed in warmer regions of both the hemispheres. The gourd family has a distinct set of morphological featres that easily distinguish it from other plant families. Generally, the plants have a fairly long tap root with lateral roots, confined to top layer of 60 cm, however in case of cucurbita root going down to 1.5 m to 1.8 m. Hence, these are well adapted to river bed cultivation and utilize subterranean moisture. The stems are branched, prostute or climbing when the nodes tough the soil under high moisture developed roots. The cucurbita pepo is bushy in nature, while some genetic stokes of muskmelon are bush type. The leaves are simple, mostly 3 to 5 lobed, variously shaped, palmate, cordate or reniform. Tendrile are borne in axils of leaves, simple in cucumber, simple or bifid in watermelon, pumpkin, gourd and they are absent in bush or erect types. Inflorescence axillary/solitary or clustered on racemes.
Flowers are large, showy (white or yellow colour petal). Staminate flowers moslty in long peducles are borne singly, but in clusters in cucumber and luffa. Pistilate flowers are borne singly in short peduncles. Usually staminate and pistilate flower borned in different axils. Hermaphordite forms which bears onyl bisexual flowers like 'Satputia' cultivar of Luffa cylindrica is rare.
Fruit is essentially a berry, the seeds are borne with partial placentation. The edible portion is placenta in cucumber and watermelon, while in muskmelon and pumpkin mostly pericarp with very little mesocarp is edible. In ridge and spongegourd endocarp is edible which later becomes fibrous and spongy. The seeds are usually many with charateristic shapes and colours. In chow-chow it is monocarpic, single seeded and viviparous.
Floral attributes of cucurbits:
Sex form:
There are three types of flowers, staminate (Androecous), pistilate (gynoecious) and hermaphordite while majority of vegetable bear hermaphordite. The cucurbits bear the above or in combination. Kalloo (1985) described following sex form :
1. Trimonoecious (0.00) -Rare in breeding lines of cucumber, muskmelon and ridge gourd.
2. Monoecious (0.0) -Predominante one - ash gourd, bottle gourd, bitter gourd, cucumber, muskmelon, pumpkin, ridge gourd, round melon, squash, watermelon.
3. Androecious (0) -Rare
4. Andromonoecious (0.0) -Muskmelon mainly.
5. Gynoecious (0) -Cucumber, muskmelon breeding lines.
6. Gyunomonoecious (0.0)
7. Hermaphorite (0) -Sponge gourd
Generally, in monoecious plants, male flowers appears first and pistilate flowers in later stages. The probable sequence of flowers on the plants under developed male, normal male, normal female, inhibited male, giant female and parthenocarpic female flowers. There may be deviations in the sequences depend upon the genotypes and environmental factors.
Sex ratio
In a typical monoecious sex forms, the number of male flowers produced is in far greater proportion than pistilate flowers. This is called sex ratio, which may ranges from 25 to 30:1 to 15:1, the later condition is advantageous and economical, because it result in greater no. of pistilate flowers/plant, consequenty higher fruit set and yield. Sex ratio is highly sensitive to environment, high N, long days and high temperature which generally promote greater numbers of male flowers.
Floral biology
Flowering in cucurbits normally starts in about 40-45 days after sowing depending upon the weather condition. The anthesis occurs in majority of cucurbits in morning exceptionally in bottlegourd, ridergourd and snakegourd.
The details on anthesis, dehiscences, poller fertility and stigma respectivity is given below:
| Name | Anthesis | Dehiscenses | Pollen Fertility | Stigma Receiptivity | References |
| Cucumber | 5.30-7 hr. | 4.30-5 hr. | upto 14 hr. | 12 hr. before to 6-7 hr. after anthesis | Choudhary & Pathak (1961) |
| Watermelon | 6-7.30 hr. | 5-6.30 hr. | 5-11 hr. | 2 hr. before and 3 hr. after anthesis | Katrodia & Dutta (1974) |
| Bottlegourd | 17-20 hr. | 13-14.30 hr. | on the day of anthesis to till next morning | 36 hr. before to 60 hrs. after anthesis | Nandpuri & Singh (1967) |
| Bittegourd | 9-13.30 hr. | 7-8 hr. | 5-12 hr. | one day before one day after | Agarwal & Singh (1957) |
| Ridgegourd | 17-20 hr. | 17-20 hr. | on the day of anthesis to 2 to 3 days in cool period & 1½ day in rainy season | 6 hr. before to 84 hr after anthesis | Singh, S.N. (1957) |
| Spongegourd | 4-8 hr. | 4-8 hr. | on the day of anthesis | 10 hr. before to 120 hr after anthesis | Singh,S.N. (1957) |
| Summer Squash | 3.30-6 hr. | 21-3 hr. | 16 hr. after anthesis | 2 hr before & 10 hr. after anthesis | Brar & Nandpuri (1969) |
| Snakegourd | 18-21 hr. | Shortly before | 10 hr. before to 49 hr. before dehiscence | 7 hr. before to 51 hr. after anthesis | Singh R.N. (1952) |
| Muskmelon | 5-6.30 hr. | 5-6 hr. | 5-14 hr. | 2 hr. before to 2 to 3 hr. after anthesis | Nandpuri & Brar(1966) |
Pollination behaviour
Anthesis, pollen dehiscences and fruit set in cucurbits are influenced by environmental factors. However, pollination generally takes place between 6 a.m. to 8 a.m. in the month of March & April in crop like cucumber, pumpkin, muskmelon and watermelon when optimum temperature range 13 to 18OC during this period. There are other cucurbits which flowers later in a day and fruit set at higher temperature of mid day as in bottlegourd and ridgegourd. In snakegourd and pointed gourd, night temperature favours anthesis during nights and fruit set in the early hours of morning when insect visit them.
The pollen production capacity is variable among the cucurbits. There is good production of pollen in watermelon, pumpkin and luffa whereas the pollen production is scanty in muskmelon and pollen is sticky due to the oily film surrounding the pollen grains.
The cucurbits are cross pollinated by nature and extent of cross pollination ranges from 60 to 80% depending upon the environment and visit of the insect. However, in muskmelon the andromonoecious condition favour a high degree of natural self pollination than in the monoecious condition. It is evident that insect do not distinguish flowers from the same or different plants at the time of voluntary pollination.
The major insects act as pollinator are mostly bees (Apix florea, A. dorsata, Nomioides sp.) are main pollinating agent. The beetles like, Conpophilous sp., moths like Plasmidia sp. etc. also helps in pollination. For getting maximum fruit set and seed yield one bee colony per acre are beneficial.
Cucumber Varietal Seed Production
Cucumber Hybrid Seed Production
Contrubuted by:Dr.BS Tomar, email:bst_spu_iari@rediffmail.com
|
|
|
|
| Contribute an Article |
We welcome agriculture articles to Publish on this site for Free!
Contribute An Article
|
|
Crops Calendar