Gene actions affecting sunflower resistance to Sclerotinia sclerotiorum measured by sclerotia infections of roots, stems and capitula

Abstract

Five sunflower inbred lines were crossed with one restorer line and F1, F2, BC1P1 and BC1P2 progenies were produced. Generation means analysis was done for all six generations, as well as the scaling test. The additive-dominance model was adequate for the analysis of the variation in three cases. Relative value of dominant gene effect (h) was higher than relative value of additive gene effect (d) and in two cases (h) was negative indicating that dominance had a negative effect on resistance to sclerotia tests on different organs. All other crosses showed significant deviation from zero for A, B, or C in all other tests indicating that the additive-dominance model was inadequate for those sets of data. In the cross PH-BC1-40A x RUS-RF-OL-168 in root and stem inoculation the dominance component (h) was positive and the dominance x dominance component (l) negative, indicating the presence of duplicate epistasis between dominant increasers. In the cross Ha-48A x RUS-RF-OL-168 in stem inoculation and crosses PR-ST-3A x RUSRF-OL-168, CMS3-8A x RUS-RF-OL-168 and PH-BC1-40A x RUS-RF-OL-168 in capitulum inoculation, (h) was negative and l positive meaning that duplicate epistasis between dominant decreasers was present. The results of our study showed that epistasis has an effect on the inheritance of sunflower resistance to sclerotia tests, and that this gene effect should be taken in account by breeders working on Sclerotinia resistance.