Response of sunflower genotypes to mid-stalk rot caused by Sclerotinia sclerotiorum

Phytopathological investigations of wild annual Helianthus annuus L. accessions and some hybrid progenies, derived from them were carried out to determine their reaction to two isolates of S. sclerotiorum under artificial inoculation of stems. Plants infection was carried out at the flowering stage. The analysis of variance for Stem disease score (SDS) and Lesions size (LS) showed a statistically significant interaction between isolate and genotype at P<0.05%. Differences in genotypes responses depending upon the isolates were established. The genotype x isolate interaction for the included wild accessions was significant, indicating that the wild sunflower genotypes differentially responded to both S. sclerotiorum isolates. The wild accessions E-129, E-115, E-110 and E-154 were consistent in terms of their responses, showing moderate resistance to both isolates. Five of the studied interspecific hybrids gave the lowest SDSs, which determined the isolate SS1914 as less aggressive than SS1941 isolate. Higher SDSs of isolate SS1941 were specified for hybrids, although they ranged to a certain extent, and determined the various degrees of hybrids susceptibility. Existence of certain interactions between studied genotypes and fungal isolates can influence the efficiency of breeding programs.