INHERITANCE OF VIRULENCE IN PUCCINIA RECONDITA ON ALLELES AT THE Lr2 LOCUS FOR RESISTANCE IN WHEAT

Abstract

The inheritance of virulence on the Lr2 alleles for resistance to the leaf rust fungus (P. recondita Rob. ex. Desm.) was investigated using selfed and "backcross" selfed cultures of race 11, F1 cultures of race 9 × race 11, race 11 × race 161 and F1 and F2 cultures of race 9 × race 161. The three host alleles Lr2a, Lr2b and Lr2c were transferred into the wheat varieties Thatcher, Red Bobs and Prelude by a series of backcrosses. Race 11, and probably race 161, have a single recessive gene, p2, for virulence on the three Lr2 alleles and an additional gene(s) that modifies or inhibits the action of the p2 gene on the three host alleles. Lines with the Lr2a gene from Webster were most resistant to the greatest number of cultures, those with Lr2b from Carina were intermediate while those with Lr2c from Brevit and Loros were least resistant. The Lr2 alleles were most effective in the Thatcher background, intermediate in Prelude and least effective in Red Bobs.