GAMETOCIDAL EFFECTS AND RESISTANCE TO WHEAT LEAF RUST AND STEM RUST IN DERIVATIVES OF A TRITICUM-TURGIDUM SSP DURUM AEGILOPS SPELTOIDES HYBRID/

Genes for leaf rust and stem rust resistance and segregation distortio n (Gc), that seemed to derive from an Aegilops speltoides ssp. ligusti ca accession, were transferred to common wheat. While the advanced bac kcrosses had normal meioses and 42 chromosomes, high levels of male an d female sterility, abnormal endosperm development and chromosome aber rations were evident. These effects were more pronounced in Gc-heteroz ygotes than in homozygotes. Gametes without Gc genes did not survive, and the Gc-associated defects were always inherited with the resistanc e. Since the resistance genes were effective against local pathotypes of the leaf rust and stem rust pathogens, an attempt was made to disru pt the Gc-system through irradiation, treatment with the mutagen N-nit roso-N-methyl-urea or growing the material at elevated temperatures. A very low frequency of the treated material showed slightly better fer tility 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).