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 × 10 4 of Eruca spp. to 0.3 × 10 4 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.

Is floral structure a reliable indicator of breeding system in the Brassicaceae?

“…These species generally had bigger flowers and floral parts than the other self-compatible species. This is consistent with Takahata and Hinata [ 7 ] and Takahata et al [ 11 ], who pointed out that the cultivated plants had been derived from self-incompatible species having larger organs and were again selected in the direction of having larger organs through breeding by man. Evolutionary transition in flowering plants from self-incompatible to self-compatible has occurred multiple times and is accompanied by changes to the floral characteristics, including smaller flowers and less pollen grains per ovule [ 12 ].…”

“…In species of the Brassicaceae , Preston [10] found that both the mean number of pollen grains per flower and the pollen/ovule ratio were significantly greater in outcrossing species than in self-pollinating species, with the pollen/ovule ratio the best indicator of the breeding system. Pollen/ovule ratio was also found by Takahata et al [11] to be closely related with the breeding system of Brassica species and allied genera. The evolutionary transition in flowering plants from outcrossing to selfing has occurred multiple times and is generally associated with a distinctive set of floral characteristics, known as the selfing syndrome (as reviewed by Sicard and Lenhard [12]).…”

“…One self-compatible species, Myagrum perfoliatum , had a pollen/ovule ratio of 7,580, higher than many of the self-incompatible species. Even though Lloyd [13], Cruden [9], Preston [10] and Takahata et al [11] all claimed that pollen/ovule ratios were good indicators of the breeding system, considerable overlap between breeding groups was likewise evident in their studies. The results of the current study have confirmed that pollen/ovule ratios cannot be used to predict the breeding system with absolute confidence.…”

Application of a probabilistic model for analysing the abortion of seeds and pods in winter oilseed rape (Brassica napus)

“…In some plants, a fruit with too few seeds may be aborted (Lee, ; Bertin, ; Ganeshaiah et al, ), resulting in late abortion. Thus, the observed variations in fruit development are due to a number of factors, including the developmental patterns of the floral organs (flower position, flower size, flower number) (Takahata et al, ), pollination limitation (Stephenson, ; Burd, ) and resource availability (Lee, ; Stephenson, ).…”