Transfer of disease resistance genes from

(McIntosh and Gyarfas 1971, Gill et al. 1983, Tomar et al. 1988, Brown-Guedira et al. 1996). Cultivated T. timopheevii has been used for wheat improvement to a greater extent than has its wild progenitor, T. araraticum. Because T. timopheevii is a cultivated species, the chances of recovering agronomically acceptable derivatives from crosses with wheat are greater. However, T. timopheevii is endemic to the country of Georgia and shows little diversity for karyotype, morphology, or seed storage proteins (Jakobashvili 1989, Badaeva et al. 1994b). T. araraticum, on the other hand, is distributed widely in the Middle East and surrounding areas (Tanaka and Ishii 1973). Because the species is found in more diverse ecological regions, chances are greater that it contains more diverse genes useful for wheat improvement. One faces many problems when attempting to introgress genes into wheat from T. araraticum. Viable hybrid seed can be recovered from crosses of T. araraticum with hexaploid wheat without performing embryo rescue, but mature F j plants are sterile (Shands 1941). Because of reduced recombination between T. aestivum and T. araraticum, recovery of desirable plant types in the progeny of the interspecific cross may be difficult. Allard and Shands (1954) isolated two agronomically acceptable wheat lines with Sr36 and Pm6, genes for resistance to stem rust and powdery mildew, respectively, from an interspecific cross ofT. timopheevii and wheat after two generations of backcrossing. The only resistance gene transferred to wheat from T. araraticum is Sr40, which confers resistance to stem rust. It was transferred from two Turkish T. araraticum accessions after six backcrosses to a stem rust susceptible hexaploid wheat line (Dyck 1992). Resistant lines were tested for traits associated with quality, and no deleterious effects were observed in the derived lines carrying Sr40. There have been limited attempts to transfer pest resistance genes from T. araraticum to common wheat. In this study, a large number of crosses were made between T. araraticum and locally adapted hard red winter wheat cultivars and breeding lines in order to: (1) describe breeding behaviour of the species with wheat; (2) transfer pest resistance genes from T. araraticum to wheat by backcrossing; and (3) determine recovery frequency and inheritance of resistance to leaf rust and powdery mildew. Attempts were made to determine whether diversity for leaf rust resistance genes occurs in T. araraticum and to sample that diversity. G. L. BROWN-GUEDIRA1, B. S. GILL, T. S. Cox, and S. LEATH