Single gene control of postzygotic self-incompatibility in poke milkweed, Asclepias exaltata L.
Most individuals of Asclepias exaltata are self-sterile, but all plants lack prezygotic barriers to self-fertilization. To determine whether postzygotic rejection of self-fertilized ovules is due to late-acting self-incompatibility or to extreme, early acting inbreeding depression, we performed three diallel crosses among self-sterile plants related as full-sibs. The full-sibs segregated into four compatibility classes, suggesting that late acting self-incompatibility is controlled by a single gene (S-locus). Crosses between plants sharing one or both alleles at the S-locus are incompatible. An additional diallel cross was done among full-sib progeny from a cross of a self-sterile and a self-fertile plant. These progeny grouped into two compatibility classes, and plants within classes displayed varying levels of self-fertility. This suggests that the occasional self-fertility documented in natural pollinations is caused by pseudo-self-fertility alleles that alter the functioning of the S-locus.
Lipow
S R
SR
Department of Botany, University of Georgia, Athens, Georgia 30602, USA. sara.lipow@orst.edu
Wyatt
R
R
D010940:Plant Proteins / Q000235:genetics*; D010944:Plants / Q000235:genetics* / Q000276:immunology
D010940:Plant Proteins