Gametophytic-sporophytic incompatibility in the Cruciferae – Brassica campestris

Gametophytic–sporophytic incompatibility in the Cruciferae–Raphanus sativus

“…sativus and B. campestris (Zuberi and Lewis, 1988), which confirm the rules of the S sporophytic gene, but also reveal a second gene, complementary to 5, which obeys the rules of the gametophytic system. This is in contrast to the published reports of work which have contained odd exceptional results which have either not been explained or have elicitated a second gene either unspecified or sporophytic in action (Putrament, 1960, Kakizaki, 1930and Kroh, 1956 The most problematical species is Eruca sativa in which the number of mating groups was so large that a precise fit to any system of genes was not possible and in which three complementary sporophytic genes were considered to be a minimum requirement (Verma et al, 1977;Lewis, 1977).…”

“…In our work on B. campestris (Zuberi and Lewis, 1988) we have no evidence for S gene changes except in dominance which is transitory and dependent upon the presence of a modifier gene. In Raphanus we have unexpectedly found a wave of S gene instability giving us three different alleles from the unstable S1.…”

“…The assumed linkage explains the unequal distribution of G genotypes found in families Vi and V2. We consider this demonstration of linkage to be of some importance because of the similarity with the linkage we have found in B. campestris (Zuberi and Lewis, 1988).…”

“…These families were analysed by Verma in Chandigarh, India, by using the restricted pollination method and counting the numbers of + andpollen grains on the stigmas. This method, which is highly successful in B. campestris, Zuberi and Lewis, 1988, is not quite so decisive in our material of Raphanus because more of the incompatible pollen does not germinate and only a minority produce the short tube which adheres to the stigmatic papillae. The compatible pollinations which we designate with a + have from 20 to 73 compatible pollen on a stigma, the -pollinations have no compatible pollen.…”

“…Most of the S and G analysis of the three generations just described was done before we adopted the novel idea of an S-G system and before the technique of restricted pollination first used by us in Brassica campestris (Zuberi and Lewis, 1988) to detect segregating + and -pollen grains from the same anther -a sine-qua-non for gametophytic We had evidence that plant 14 was heterozygous for G12. Because the compatibility of the S genotypes overrules any G incompatibility the G alleles would be transferred through the pollen without restriction and therefore we should obtain more than one G genotype in the progeny.…”