Marker trait association and candidate gene identification for brown rust disease in sugarcane

Abstract

Brown rust (caused by Puccinia melanocephala H. & P. Sydow) is one of the most devastating diseases in commercial sugarcane production. It could reduce sugarcane yield by up to 50% depending on the susceptibility levels of cultivars. Breeding disease‐resistant cultivars is the most effective, economical, and environmentally friendly option to control brown rust. A genome‐wide association study was conducted on a field trial using 432 sugarcane clones following an augmented design with two replications. Brown rust was screened using the whorl inoculation method over two crop cycles. The genotype data were obtained through target enrichment sequencing technologies. The gene actions considering six different models and marker dosage effects were included during the marker‐trait analysis. A total of seven, nine, and seven nonredundant marker‐trait associations were identified for plant cane, first ratoon, and across two crop cycles, respectively. The most significant (p‐value 6.17E−20) marker (chr01p59833543) has the additive effect of −0.63 for the diplo‐additive model and reduced disease severity the most (41.35%) due to heterozygote (AG) over homozygote allele (AA) combination in the tested clones. Gene annotation of the monoploid sugarcane genome R570 suggested that six putative candidate genes were co‐located with significant markers associated with brown rust resistance in sugarcane. The putative candidate genes regulated the formation of a cell wall barrier that plays a crucial role in controlling brown rust pathogen infection. The results of this study will open the path to exploiting new resistance sources for brown rust resistance in commercial sugarcane.