EFFECTS OF ALIEN AND INTRASPECIES CYTOPLA SMS ON EXPRESSION OF MAJOR NUCLEAR GENES FOR WHEAT RESISTANCE TO BROWN RUST .3. INTRALINE HETEROGENEITY OF RECIPROCAL HYBRIDS IN F-2

Resistance to two brown rust clones of reciprocal hybrids from the cro ss of homozygous susceptible plants of the Penjamo 62 euplasmatic cult ivar and its alloplasmatic lines bearing cytoplasms of Triticum dicocc oides var. fulvovillosum, Aegilops squarrosa var. typica, and Agropyro n trichophorum with isogenic lines of the cultivar Thatcher (Th) carry ing the genes Lr1, and Lr9, Lr15, Lr19 was analyzed. Segregation in pr ogeny of the F-2 hybrids between cultivar Th and the Penjamo 62 indivi dual plants evidenced differences in genes that exhibited complementar y interaction. Variation in a resistant: /susceptible ratio in the F-2 from crossing of isogenic lines with Penjamo 62 plants and its allopl asmatic lines also showed intraline heterogeneity of the stock materia l. Varying segregation ratios may arise from differences between the o riginal plants both in nuclear and cytoplasmic genes. In the first cas e, we suppose that variation in complementary nuclear genes or modifie rs of the major Lr genes can occur. In the second case, we suggest the existence of specific expression and (or) transmission of the nuclear resistance genes in hybrids due to differences between the original p lants for plasmagenes involved in host-pathogen interactions.