S-RELATED PROTEIN CAN BE RECOMBINED WITH SELF-COMPATIBILITY IN INTERSPECIFIC DERIVATIVES OF LYCOPERSICON

Stylar proteins involved in the self-incompatible (SI) response of Lyc opersicon hirsutum have been identified and mapped to the focus that c ontrols SI (S locus). L. esculentum, a self-compatible (SC) species of cultivated tomato, does not display these proteins. Hybrids between S C L. esculentum and SI L. hirsutum are self-sterile despite these indi viduals bearing pollen containing the S allele of L. esculentum. In pr ogeny derived from backcrossing the hybrids to L. esculentum, there wa s a strong correlation between the presence of the S allele from L. hi rsutum and self-infertility. However, this relationship was uncoupled in a number of backcross (BC) progeny. The SI response appeared to be nonexistent in two self-fertile BC individuals that were heterozygous for the S allele of L. hirsutum, based on Mendelian segregation of a t ightly linked DNA marker, CD15, in selfed progeny. Among these progeny self-fertile individuals that were homozygous for the L. hirsutum all ele of the linked marker were also determined to be homozygous for an S-related protein of L. hirsutum through test crosses with L. esculent um. Therefore, plants were produced that were homozygous for a functio nal S allele but were self-fertile. This result and other evidence sug gest that the S-related proteins are not sufficient to elicit a self-i ncompatible response in L. esculentum and that there is a mutation(s) in L. esculentum somewhere ether than the S locus that leads to self-c ompatibility.