Sex expression in cucurbit: Technique to raise female flowers for double yield, Training & Seed production

Introduction:

Most of the cucurbits are monoecious in nature and bears male & female flowers separately on the same plant. Similarly, andromonoecious sex form is also common in cucurbits where male & hermaphrodite flowers are borne separately in same plant. Monoecious cucurbits include cucumber, watermelon, long melon, pumpkin, bottle gourd, ridge gourd, snake gourd, chayote etc. Similarly, andromonoecious sex form is common in bottle gourd, ridge gourd, sponge gourd, snake gourd, muskmelon, etc.

Sex forms in cucurbits:

  • Monoecious (♀ and ♂): Cucumber, Musk melon, Pumpkin, Summer squash, Winter squash, Water melon, Sponge gourd, Round melon, Bottle gourd, Bitter gourd.
  • Gynoecious (♀): Cucumber, Bitter gourd, Musk melon, Watermelon, Ridge gourd
  • Androecious (♂): Cucumber, Musk melon
  • Dioecious (♀ and ♂ in separate plant): Pointed gourd, Ivy gourd,
  • Andromonoecious (♂ and in same plant): Muskmelon, Water melon, Cucumber
  • Gynomonoecious (♀ and in same plant): Cucumber, Musk melon, Ridge gourd
  • Trimonoecious (♂, ♀and in same plant): Cucumber
  • Hermaphrodite: Ridge gourd (Satputia)

Fruit set & yield of the crop depends upon the number of female flowers. Generally, male flowers open first & their number is comparatively larger than of female flowers. High temperature, longer day light, high nitrogen fertilization etc. are the major factors inducing maleness in cucurbits. Although sex expression and sex ratio are varietal characteristics, they can be modified by providing suitable environment. Both plant growth regulators and nutrients at proper concentration modify sex. Usually, 2-4 true leaves stage is the critical stage for suppression or promotion of either sex. There are several growth regulators available for sex modification and are broadly classified into two groups:

  1. For promotion of staminate (male) flowers:

  • A single application of AgNo3 (600 ppm {600 mg/liter of water}) before opening of flowers.
  • Application of high concentration of GA3 (1000ppm), first at 2 leaf stage and then after 10-15days interval.
  1. For promotion of pistillate (female) flowers:

  • Application of Ethrel (200 – 250 ppm) at 2nd & 4th true leaf stage.
  • Spray of Maleic Hydrazide (50 – 100 ppm) at 2nd & 4th true leaf stage.
  • Spray of 100 ppm of 2-Napthalene acetic acid (NAA), 2ppm boron, 50 ppm 2,3,5 tri-iodobenzoic acid (TIBA).

Major cucurbits & commonly used growth regulators are given below in the table:

Cucurbit Growth regulator
Cucumber Ethrel 200 ppm, MH 100 ppm
Bitter gourd NAA 100 ppm, 2-CEPA 200 ppm
Bottle gourd MH 50 ppm, 2-CEPA 100-200 ppm
Sponge gourd Ethrel 250 ppm, MH 100 ppm
Watermelon MH 50 ppm, TIBA 50 ppm, boron 2 ppm
Pumpkin Ethrel 250 ppm
Muskmelon MH 200 ppm

Training & Bower system:

Training of plants in bower system is an essential practice foe getting higher yield and uniform quality fruits in cucurbits.. For preparation of bower system, bamboo, cement, wooden or iron angle poles may be used. Pole height must be 5-6 ft from the surface of the soil and the pole are buried 1-1.5 feet in the soil. Th distance between two poles should be 10 ft and the initial pole has tilted poles to support the main pole. Criss-cross netting is done to make bower by wires. Bower system is useful by:

  • Distance between pits may be reduced so more plants can be accommodated.
  • quality fruits of uniform size may be harvested.
  • Easy in harvesting.
  • No rotting of fruits.
  • Early inter-culture operation and plant protection measure can be applied.

Seed Production in Cucurbit:

Seed production in cucurbit is quite easy however isolation distance is must. All melons, pumpkins, cucumbers and gourds are highly cross-pollinated. Different varieties should not be put together, otherwise they would be contaminated by cross-pollination. Sponge gourd and ridge gourd should not be put together in the same field for seed production as they cross with each other.

Similarly, most of the pumpkin varieties belong to the genus Cucurbita, which are Cucurbita moschata & Cucurbita maxima. Crosses may occur between these two species. The producer therefore must know the species to which his varieties belong and should maintain standard isolation distance pf 800 m between two varieties. Care should be taken to rogue out the off type plants, weeds and other debris from the seed multiplication block in the field.

Seed should be extracted from dried fruits in bottle gourd, sponge gourd, and ridge gourd and from ripe fruits in bitter gourd, ash gourd, pumpkin, cucumber, watermelon & muskmelon. Seeds may be dried in the sun or mechanical driers may be used for it.

After the seed has been dried proper storage of seed away from insect pest & disease prone areas relatively cool temperature & drier must be selected to prolong the viability of seeds.

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