Field Evaluation of Sugarcane Orange Rust for First Clonal Stage of the CP Cultivar Development Program

Consistent development of high-yielding sugarcane (a complex hybrid of Saccharum spp.) cultivars with resistance or tolerance to biotic and abiotic stresses is critical to commercial sugarcane production. Currently, orange rust (caused by Puccinia kuehnii E.J. Butler) is a big challenge for the sugarcane production in Florida, USA. A better understanding of sugarcane genotypic variability in response to orange rust disease will help optimize breeding and selection strategies for disease resistance. Orange rust ratings, scaled from non-infection (0) to severe infection (4) with intervals of 0.5, were recorded from genotypes at the first clonal selection stage (Stage I) of the Canal Point sugarcane breeding and cultivar development program in Florida. Data were collected from all 14,272 and 12,661 genotypes and four replicated reference cultivars, CP 78-1628, CP 80-1743, CP 88-1762 and CP 89-2143, in July-August 2012 and 2013, respectively. Mean rust rating, % of rust infection and rust severity in each family (i.e., progeny of the cross from a female and male) and female parent and their Coefficients of Variation (CV) within and among families (females) were estimated. Results indicated that considerable variation exists in rust tolerance among families or females. The families or females for their progenies with the high susceptibility or resistance to orange rust were identified and ranked. The findings of this study are useful for evaluating sugarcane crosses and parents for rust disease and can help breeders use desirable parents for crossing and improve genotypic resistance to orange rust in the sugarcane breeding programs.