Peculiarities of Inheritance of Pollen Fertility Restoration Trait in Sunflower with Cytoplasmic Male Sterility

The progenies from crosses of a sterile VIR116A line with PET1 CMS with pollen fertility restorer RIL130, VIR210, and VIR740 lines, differing in the type of cytoplasm and the presence of diagnostic molecular markers of the Rf1 gene, were studied. The pollen of F1 plants of all three cross combinations was highly fertile (89.9–98.3% of stained pollen grains, PG). Each of the F2 populations (VIR116A × RIL130, VIR116A × VIR210, and VIR116A × VIR740) segregated for the pollen fertility trait in a ratio 3 (fertile) : 1 (sterile). Among fertile F2 genotypes, “low pollen” ones were identified, in which there was less pollen than normal during a visual estimation. Their frequency was approximately 9% of the total number of plants in each of the populations, which is consistent with the results obtained previously during the analysis of other hybrid combinations. In cytological analysis, the pollen of “low pollen” plants was characterized by a decreased (as compared with highly fertile plants) frequency of fertile PG (80–100 and 11–78%, respectively) and higher content of anomalous PG (in “low pollen” plants up to 88.5%, in plants with normal level of fertility up to 18%). Using HRG01 and HRG02 molecular markers, the presence of the Rf1 dominant allele in the genotypes of fertile F2 plants (including “low pollen” ones) was confirmed, indicating their high diagnostic value. Possible genetic mechanisms of the occurrence of “low pollen” F2 segregants are discussed.