Breeding of Vegetable, Spice and Tuber crops (2+1)

Self-pollination

• Many cultivated plant species reproduce by self-pollination. Plant species showing self-pollination, i.e., inbreeding, are generally annuals or, in any case, short lived.These species, as a rule, must have hermaphrodite flowers. But in most of these species, self- pollination is not complete and cross-pollination may occur up to 5%.The degree of cross-pollination in self-pollinated species is affected by several factors, e.g., variety, environmental conditions like temperature, humidity and location.

Mechanism promoting self-pollination
The various mechanisms that promote self-pollination are

1. Cleistogamy: In this case, flowers do not open at all. This ensures complete self pollination since foreign pollen cannot reach the stigma of a closed flower.
2. Chasmogamy: In some species, the flowers open, but only after pollination has taken place.
3. In crops like tomato (S.lycopersicum) and brinjal (S. melongena), the stigma is closely surrounded by anthers, pollination generally occurs after the flowers open. But the position of anthers in relation to stigma ensures self-pollination.
4. In some species, flowers open but the stamens and the stigma are hidden by other floral organs.
5. In peas (P.sativum), the stamens and the stigma are enclosed by the two petals forming a keel.
6. In a few species, stigma become receptive and elongate through the staminal columns.This ensures predominant self-pollination.