genetic analysis of crown wart (urophlyctis leproides) resistance in sugar beet

the crown wart disease caused by urophelyctis leproides on sugar beet is very important in the growing areas of north khuzestan influencing quantity and quality of the crop. the objectives of our research were to estimate general combining ability (gca) and specific combining ability (sca) of sugar beet lines as well as the gene action governing resistance to this disease. a randomized complete block design with three replications was used to evaluate six parents and their 15 f1 crosses. the method 2 and model 1 of griffing and also hayman method were used to estimate variance components. resistance indices of the disease, ratio of gal weight to root weight and gal weight were measured on these genotypes.. the genotypic effects were significant for the disease indices. gca and sca were also significant indicating the importance of both additive and non-additive gene effects in controlling the disease resistance. the results from hayman analysis showed complete-dominance for the traits under study and resistant genes appeared to be recessive. a recurrent selection program with new recombination in each generation for pyramiding valuable genes in inbred lines is suggested before selecting useful hybrid combinations.