Gametocidal effects and resistance to wheat leaf rust and stem rust in derivatives of a Triticum turgidum ssp. durum/Aegilops speltoides hybrid

Abstract

Genes for leaf rust and stem rust resistance and segregation distortion (Gc), that seemed to derive from an Aegilops spetroides ssp. ligustica accession, were transferred to common wheat. While the advanced backcrosses had normal meioses and 42 chromosomes, high levels of male and female sterility, abnormal endosperm development and chromosome aberrations were evident. These effects were more pronounced in Gc-heterozygotes than in homozygotes. Gametes without Gc genes did not survive, and the Gc-associated defects were always inherited with the resistance. Since the resistance genes were effective against local pathotypes of the leaf rust and stem rust pathogens, an attempt was made to disrupt the Gc-system through irradiation, treatment with the mutagen N-nitroso-N-methyl-urea or growing the material at elevated temperatures. A very low frequency of the treated material showed slightly better fertility and seed development. However, these effects did not persist in subsequent generations and were apparently not strong enough to allow the recovery of segregates which had lost the Gc gene(s).