The article highlights the results of studying hybrid combinations of common onion to the Botrytis allii Munn pathogen. It is found out that as for the combinations being studied the resistance to pathogen was inherited as dominant, intermediate or recessive trait. Better resistance to neck rot was inherent in the hybrid combinations which parents comprised resistant and immune varieties, insofar as the determination of inheritance coefficient has indicated F1 hybrids have this characteristic expression dependant by 50 to 78% on the parental plant (h2 =0,50–0,78). Studying the determination of the impact of both parental components on inheritance of the resistance to B. allii pathogen showed that the regression coefficient subject to hybrid combination fell within R = 0,12–0,39, while the resistance coefficient within 0,24–0,78, respectively. Efficiency of selection is proved by the trait of resistance to neck rot based on the populations of Grandina х Mavka, Olina х Grandina, Grandina х Skvyrska і Skvyrska х Grandina, as their respective inheritance coefficient reached the level of 0,42 to 0,78.