Minimum amount of resources for detecting different performances of sunflower hybrids to white rot

Sunflower is susceptible to Sclerotinia sclerotiorum attacks on capitula. Consequently, breeding programs must develop hybrids moderately resistant to white rot (WR) in order to minimize potential disease damages. The selection of hybrids for their WR performance is made in trials across several environments but this strategy entails a high cost in breeding programs. The objective was to find an adequate combination of resources that allows differentiating hybrids based on their WR performance. In Balcarce 37 cultivars, distributed in a randomized complete block design with 3 replications, were inoculated with S. sclerotiorum ascospore during 3 years. In diseased plants, the relative incubation period-PIR and the relative daily growth of the lesion-CLR (two components of the partial WR resistance) were measured. For each hybrid, BLUPs were estimated using, first, 108 plants/hybrid resulting from the combination of 3 years, 3 replications and 12 plants/plot (i.e. all the available resources were used). And then estimations were made for those combinations involving lower levels of resources. The least significant difference test differentiated hybrids by their BLUPs. For both variables, differential performances were detected with all of those resources as well as lower levels of them. Results showed the possibility to differentiate hybrids by their PIR and CLR performance in the same trial, saving until 50% of the available resources, without the genotypic evaluation being significantly affected.