SEGREGATION FOR CROWN AND STEM RUST RESISTANCE IN DIPLOID AND AUTOTETRAPLOID AVENA STRIGOSA

Abstract

The inheritance of resistance to race 294 of crown rust and race 13A of stem rust in Avena strigosa, variety CD. 3820, was studied in the diploid and autotetraploid. At the diploid level, two independently inherited genes were involved, one giving resistance to crown rust and the other to stem rust. At the autotetraploid level, the same two genes segregated independently in a typical tetrasomic manner. For the crown rust data the observed segregation was close to that expected for random chromosome segregation, while for stem rust it was close to that expected for random chromatid segregation. The autotetraploid crown and stem rust data and the observed quadrivalent frequencies in crosses 1094 and 1095 were used to estimate [alpha] and its two components a and e. The possibility is discussed of differences in frequencies of quadrivalent formation between the two sets of chromosomes with the two genes in question.