Incompatibility in Cosmos bipinnatus

Abstract

Recent workers on Parthenium argentatum (Gerstel, 1950) and Crepis frtida (Hughes and Babcock, 1950) have described a novel type of incompatibility. To explain the results, one incompatibility gene is postulated with multiple alleles which act individually in the style as in Xicotiana, but the behaviour of the pollen is determined by the sporophyte and the alleles exhibit dominance, both features associated with the heteromorphic outbreeeding types. Thus, for the first time a system has been described in two species of the Composit which combines genetic features typical of both the heteromorphic and homomorphic types of incompatibility. Regular features of this new system are reciprocal differences in compatibility, incompatibility between some F1 plants and one or both parents, and plants which are homozygous for one allele. There are two examples of this new breeding system in the Composite and it is therefore of interest to find out whether it is typical of the family as a whole. A report on incompatibility in Cosmos bipinnatus (Little, Kantor and Robinson, 1940) concluded that the mating system was similar in all respects to that of ,Nicotiana. The experiments, however, were not designed to show reciprocal differences in compatibility, or incompatibility between progeny and parents and these must be considered if the Composite type of system is to be distinguished from any other. This paper describes a reinvestigation of the mating behaviour of C. bipinnatus. * C. bipinnatus is always classified as a "short day" plant. It is probable that, in captivity, selection has favoured plants with less rigid light requirements. Many horticultural varieties are now indifferent to day length in respect of flowering time. Recently a family of Cosmos segregated into plants which flowered in "long day" conditions and others which did not. The genetics of this difference is being investigated.

The genetic control of self-incompatibility in Linanthus parviflorus (Polemoniaceae)

“…Analysis of crossing relationships in the sibships with three or more incompatibility types clearly eliminates the possibility that dominance is present only in pollen, as is true in composites (Crowe, 1954;Davidson & Stace, 1986). All of the observed patterns of incompatibility are consistent with SSI models in which dominance is seen in both tissues, as well as models with dominance in the stigma only.…”

“…Bateman, 1954;Ockendon, 1974;Ford & Kay, 1985) and Asteraceae (e.g. Gerstel, 1950;Crowe, 1954;Davidson & Stace, 1986), and more recently, has been described in the Convolvulaceae (Martin, 1968;Kowyama et aL, 1980), Betulaceae (Thompson, 1979), Caryophyllaceae (Lundqvist, 1979, 1990) and Sterculiaceae (Jacob, 1980). Gametophytic SI appears to be the more common form, known in 14-17 plant families (Charlesworth, 1988).…”

Incompatibility in Theobroma cacao

“…Cosmos is apparently intermediate between Crepis and cacao, having some alleles independent in the style that are dominant in the pollen. It has been pointed out (Crowe, 1954) that there is some evidence for dominance between the alleles of the style in Parthenium, although this possibility is not mentioned by Gerstel. The raising of compatibility between sibs of cacao lowers the outbreeding efficiency (Bateman, 1953) but conserves generative material where the cacao population is restricted, as it frequently is, in the plant's natural habit.…”

Outcrossing rate and self-incompatibility in the colonizing species Senecio squalidus

“…The occurrence of reciprocal differences in cross-compatibility between some pairs of parent plants is a feature of sporophytic SI (Lewis, 1979) as is the production of trinucleate pollen and inhibition of pollen at the stigma surface, both of which occur in S. squalidus (R. Ingram & D. F. Marshall, personal communication). It seems, therefore, that S. squalidus possesses a homomorphic sporophytic SI system, as do other self-incompatible species of the Compositae that have been investigated (Gerstel, 1950;Hughes & Babcock, 1950;Crowe, 1954). The fact that a fairly large pro- which the species is likely to have passed through during its introduction to the U.K., all British populations of S. squalidus may contain few S alleles relative to numbers of S alleles normally found in populations of other species that exhibit homomorphic sporophytic self-incompatibility (Karron et al, 1990).…”