DETECTION AND INHERITANCE OF STYLAR RIBONUCLEASES ASSOCIATED WITH INCOMPATIBILITY ALLELES IN APRICOT

Stylar proteins were surveyed by non-equilibrium pH gradient electrofo cusing to identify S-RNases associated with gametophytic self-incompat ibility in nine apricot cultivars. RNase activities associated with th e alleles of incompatibility S-1, S-2, S-5, and S-6 and with the allel e of compatibility Sc were clearly identified. Two other bands that we considered related to the alleles S-3 and S-4 were unique to cultivar s Sunglo and Harcot, respectively. Two generations of 17 seedlings fro m the cross Moniqui x Pepito and 38 from Gitano x Pepito were used to determine the inheritance of the S-RNases. Inheritance of these RNase bands followed the expected segregation ratios and the band combinatio ns correlated perfectly with the known self-incompatibility status of the seedlings determined after self-pollination and observation of pol len tube growth. All evidence presented in this study strongly suggest s that RNases are associated with gametophytic self-incompatibility of apricot and that RNases may be the S-gene products. This is the first report identifying S-RNases and describing the inheritance of these S -RNases in apricot.