Genotypic responses and diallel analysis for an early resistance test to Sclerotinia sclerotiorum in sunflower

The evaluation of sunflower genotypic performance against Sclerotinia sclerotiorum infections is important for understanding its usefulness as source of resistance. In the field, artificial and natural resistance tests provide important information that can be used in the selection of the best materials, however the procedures for resistance tests are usually both expensive and laborious. This work describes the performance of sunflower genotypes of broad genetic base at an early stage of plant development using a resistance test carried out under controlled conditions in the greenhouse. Statistical analysis detected highly significant genotypic responses and the combined abilities effects among the evaluated populations and their offspring, obtained by a diallel crossing system method 2 for dead seedlings (%) at 25 days after S. sclerotiorum infection on the basal stem.The methodology allowed superior parents to be detected and crosses to be furthered in the selection for S. sclerotiorum resistance. The usefulness of the evaluated genetic materials and the early resistance test in sunflower breeding plans is discussed.