BREAKDOWN OF SELF-INCOMPATIBILITY IN TETRAPLOID LYCOPERSICON-PERUVIANUM - INHERITANCE AND EXPRESSION OF S-RELATED PROTEINS

Lycopersicon peruvianum displays gametophytic self-incompatibility (GS I). We have isolated self-compatible (SC) tetraploids of L. peruvianum from tissue-cultured leaves and have explored the expression and inhe ritance of their S-related proteins. The S-related protein profiles of styles of SC tetraploids were indistinguishable from the diploid self -incompatible (SI) explant source based on SDS-PAGE. All progeny obtai ned from self-fertilization of two tetraploids were SC. Cloned cDNA se quences of the S-related proteins were used to deter-mine the inherita nce of this locus in these progeny through Southern hybridization. The allelic ratio, as determined from the intensity of DNA restriction fr agments, was consistent with the predicted ratio if only pollen bearin g two different alleles was successful in achieving fertilization. All progeny obtained had at least one copy of each allele, and individual s fully homozygous for either allele were not found, indicating that p ollen grains bearing two identical alleles were inhibited. In addition , the level of expression of the S-related proteins in the progeny cor related with the allelic dosage at the DNA level. We demonstrate that the observed self-compatibility in the tetraploids was not caused by a n alteration in the expression of S-related proteins.