Screening of historical and current Upland and Pima cotton germplasm for resistance to Rhizoctonia solani

The results of the R. solani screening found no significant differences among 85 Upland and 10 Pima cotton genotypes, which were all similarly susceptible to R. solani based on data for root rot and fresh root weight. While Upland and Pima cotton make up the majority of cotton grown worldwide, the lack of resistance identified in both historical and newer Upland and Pima germplasm suggests a pressing need for further exploration and selection of novel sources of resistance within the vast genetic diversity of different domesticated and wild cotton species.