NON-MENDELIAN AND SKEWED SEGREGATION OF DNA MARKERS IN WIDE CROSSES OF THE BEAN RUST FUNGUS, UROMYCES-APPENDICULATUS

The inheritance of DNA markers was investigated in 27 F-2 progeny from a single F-1 hybrid derived from a wide cross in Uromyces appendicula tus. This cross was unusual because asexual spores were used to fertil ize sexual fruiting structures. Sixty percent of the DNA markers faile d to segregate according to simple Mendelian ratios. Segregation bias was evident, in that F-2 progeny inherited on average 91% of maternal bands and 52% of paternal bands, which deviates significantly from the expected value for each of 75% for dominant markers. Because of these distortions, linkage mapping was not possible with this population. E valuation of two F(1)s from a second wide cross, reciprocals obtained by normal fertilization, also showed non-Mendelian inheritance of one of three co-dominant RFLPs and five of six isozyme markers, indicating that the method of crossing was probably not responsible for the abno rmal segregation patterns in the first cross. Either genetic incompati bility, similar to that of an interspecific cross, or selection of par ticular genotypes could explain the genetic anomalies reported here.