Genetics of rust resistance and cytogentic studies in a derivative of wheat (Triticum aestivum L.) x Aegilops speltoides

An experiment was conducted to study the mode of inheritance of resistance to leaf rust and stem rust in an interspecific derivative Selection 2427 (Sel.2427). The genetic analysis in F₂ and BC₁ generations revealed that resistance against selective pathotypes of leaf rust, 77-5 and 77-7, and stem rust, 40A, and 117-6 is controlled by a single dominant gene. The resistance in Sel. 2427 appeared to be diverse and may be useful in wheat improvement. Cytological analysis at first meiotic metaphase in monosomic and disomic F₁ plants derived from the crosses between twenty one monosomic lines of Chinese Spring and Sel.2427 showed that the number of bivalents differed significantly. Precocious separation of bivalents occurred uniformly in the PMCs irrespective of euploidy or aneuploidy. Probably the segment translocated from Aegilops speltoides to wheat chromosome in Sel. 2427 affected the homologous chromosome pairing leading to precocious separation and inducing desynapsis. The segment also affected pollen fertility making F₁ hybrid partially male sterile resulting in low seed set in F₁ and F_2. Sel. 2427 may be useful material for studying chromosome pairing and chiasma formation.