Optimization of resource allocation in field phenotyping of sunflower for components of partial resistance to Sclerotinia sclerotiorum on capitula

Abstract

In sunflower breeding, plant phenotyping of white rot (WR) resistance requires a significant amount of resources. Thus the present study aimed to evaluate the possibility to make a more efficient phenotyping of WR resistance in sunflower hybrids per unit of allocated resources. The Degree of Genetic Determination (DGD) estimated from 37 commercial hybrids evaluated by their relative incubation period (RIP) and relative daily lesion growth (RDLG) for 3 years (y) in field experiments designed with 3 replications (r) and 12 plants/plot (pl/p), i.e. 108 plants/hybrid (pl/h), was compared with DGDs estimated using < 108 pl/h. When using fewer resources, DGD values were estimated with less precision in all year-replication-plant/plot combinations. The bias between the DGD averages estimated and the benchmarked DGD values of 0.78 (RIP) and 0.63 (RDLG) and, consequently, the inaccuracies of such estimations increased gradually. The 3y-2r-6pl/p combination was the level of allocated resources showing a still acceptable relative genotypic variability detected for RIP, given that a 100% probability of the DGD estimated was higher than the proposed threshold (DGD = 0.60) value, although the probability for RDLG was quite lower. That combination also resulted in a not-to-be overlooked gain in relative genotypic variability per unit of allocated resources in relation to that with 108 pl/h. So, the cost associated with resources, such as land, seeds, time, and personnel, allocated to assess WR resistance could be reduced without significantly altering the accuracy and precision of the DGD values estimated respect to the benchmarked ones.