Genotypic variation for floral characters in Brassica and allied genera with special reference to breeding system

Abstract

The five floral characters, i.e., number of pollen grains per flower, pollen grain diameter, anther length, number of ovules per flower and pollen-ovule ratio (P/O), were studied on 119 strains of 53 species in Brassica and allied genera with respect to the breeding system. There were large variations in all five characters among species, especially the number of pollen grains, number of ovules per flower and P/Os showed larger variations. The values range widely from 23-24 × 104 of Eruca spp. to 0.3 × 104 of Diplotaxis viminea and from 19800 of Hutera rupestris to 100 of D. viminea in the number of pollen grains and P/Os, respectively. The P/O was significantly correlated to the energy cost per flower. Both indices were closely related with the breeding system of species. The lowest P/Os and the smallest energy costs were found in the obligate autogamous species, while the xenogamous species showed higher and larger, but more fluctuating P/Os and energy costs. In the facultative autogamous amphidiploid species in Brassica crops, both P/Os and energy costs per flower were similar to those of xenogamous species; however, P/Os were lower than their xenogamous parental species. The relationships of P/Os with natural selection are also discussed.