NUCLEAR-CYTOPLASMIC INTERACTIONS IN WHEAT RESISTANCE TO FUNGAL PATHOGENS .8. SPECIFICITY IN INTRASPECIES CYTOPLASMIC EFFECTS IN COMPATIBLE COMBINATIONS BETWEEN TRITICUM-AESTIVUM AND BROWN RUST

Using seedlings of 29 isoplasmatic lines of the cultivar Leningradka, which carries cytoplasms of different cultivated common wheat samples, the reproductivity of five brown rust clones and a mixture of them co ntaining equal amounts of these clones was studied. Pathogen clones va ried in the virulence genes in several isogenic lines of the cultivar Thatcher and infected cultivar Leningradka. A highly significant effec t of the plant cytoplasm on mean-spore-forming ability per cm(2) (MSFA ) of leaf surface was shown using ANOVA. The contribution of the ''cyt oplasm'' factor to variability of this parameter of quantitative resis tance depended on the pathogen used and ranged from 3.47% tb 12.21%. V arying the reproductivity of fungus clones with different virulence an d mixing them on isoplasmatic lines evidenced the specificity in modif ying cytoplasm effect of cultivated samples on the level of quantitati ve wheat resistance (MSFA) to brown rust. The relative similarity of s ubstitution lines for this parameter upon infection with five clones a nd a model population, revealed by cluster analysis, allowed us to dis criminate groups of cytoplasms with similar effects on quantitative re sistance to brown rust.