Molecular Detection of Bru1 Gene and Identification of Brown Rust Resistance in Chinese Sugarcane Germplasm

Abstract

Sugarcane brown rust induced by Puccinia melanocephala is an important global disease. Bru1 is a major brown rust resistance gene and has been shown to provide broad-spectrum resistance against various brown rust pathogen strains originating from different countries. Thus, brown rust resistance genes have important implications for sugarcane brown rust resistance breeding programs. The objectives of this study were to (1) assess the level of resistance of common sugarcane crossbreeding parents to P. melanocephala, (2) determine the distribution of the Bru1 gene in common sugarcane crossbreeding parents in China, (3) screen, evaluate, and select rust-resistant parental lines to improve the efficiency of breeding for brown rust resistance. Brown rust resistance in 101 common sugarcane breeding parents was collected from the Chinese National Nursery of Sugarcane Germplasm Resources and was scored and identified at the seedling stage and was assayed for the presence of the brown rust resistance gene Bru1. The results showed that Bru1 was detected in 48 (47.5 %) resistant clones out of the 101 tested parental lines, indicating that brown rust resistance in common sugarcane breeding parents in China is primarily controlled by Bru1. The apparent absence of Bru1 from the other 29 resistant and 24 susceptible parental lines suggested that they may carry brown rust resistance-associated genes other than Bru1. These results may facilitate future efforts to breed varieties with improved resistance to brown rust and may provide additional resistant parental lines for selecting and planting elite-resistant varieties to effectively control brown rust disease in sugarcane.