Molecular characterization of Puccinia melanocephala, the causal agent of brown rust, in Tucumán, Argentina

BERTANI, R; FUNES, C.; CASTAGNARO, A.P.; PERERA, M. F.; GONZALEZ, V; JOYA, C.; CUENYA, MI

San Miguel de Tucumán

Congreso; ISSCT XXX Congress; 2019

Sugarcane brown rust is one of the main diseases affecting sugarcane and Puccinia melanocephala Syd. & P. Syd., its causal agent, has been reported as one of the most economically important fungal pathogens worldwide. For that reason, the knowledge of its genetic diversity should be considered when developing resistance breeding strategies. The aim of this study was to estimate the genetic diversity of P. melanocephala in the sugarcane-growing area of Tucumán, Argentina, using a reproducible molecular technique. 137 leaf samples with brown rust symptoms were collected during 2011, 2012 and 2013 seasons in 40 locations in Tucumán from 33 sugarcane genotypes. Samples were obtained by harvesting urediniospores from pustules with a brush and total DNA extraction was optimized. Samples were characterized by AFLP markers and eight of them corresponding to different clusters according to AFLP analysis were also characterized by seven SSR primer pairs. Only 73 out of 137 spore samples presented adequate DNA quantity and quality for the subsequent analysis. From a total of 255 AFLP markers, 92.2% were polymorphic. The high percentage of polymorphism detected indicated high pathogen diversity where no apparent correlation between P. melanocephala samples and sugarcane genotype, location sampled, or year of collection was observed. From a total of 18 SSR markers obtained, 88.9% were polymorphic. There was a positive and statistically significant correlation between the distance matrixes obtained with AFLP and SSR markers. Results revealed that both AFLP and SSR were useful to examine the molecular polymorphism of P. melanocephala samples and might have a significant contribution to the knowledge of its genetic diversity. Due to the high level of polymorphism detected in P. melanocephala in Tucumán Province, breeders should be alert as the durability of the resistance could be continuously threatened.