ABSTRACT
Brown rust caused by the fungus Puccinia melanocephala is an important disease affecting sugarcane (Saccharum spp.) and is present in almost all growing areas. A major effect gene, Bru1, was described as a durable resistance source in sugarcane against isolates of P. melanocephala. The aim of this study was to evaluate the efficiency of two molecular markers strongly associated with Bru1 gene, R12H16 and 9O20-F4-RsaI, for prediction of genetic resistance to brown rust in sugarcane varieties. Thus, this study included 14 RB varieties, developed by RIDESA (Interuniversity Network for the Development of the Sugarcane Industry), which were among the 10 most cultivated varieties in the central-south region of Brazil in the period of 1974-2015. To evaluate the disease in the field an experiment was conducted in randomized blocks with four replicates. The severity of brown rust was quantified according to a diagrammatic scale ranging from 1 (most resistant) to 9 (most susceptible), and the obtained data were analyzed by using a generalized linear mixed model (GLMM). Concomitantly, total DNA was extracted from the 14 varieties, followed by amplification of the molecular markers, which were classified into haplotypes. Out of the total varieties, 12 had no symptoms of the disease and showed 99.35% probability of being resistant according to analysis via GLMM; among them, 91.66% were haplotype 1, i.e., had the presence of both markers associated with Bru1 gene. Therefore, we can conclude that the molecular markers R12H16 and 9O20-F4-RsaI were highly efficient in predicting resistant phenotypes and that Bru1 gene is probably the main source of sugarcane resistance to brown rust in commercial fields in Brazil.
Keywords
Saccharum spp.; breeding; Puccinia melanocephala; Bru1; disease resistance
