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

BERTANI RP; PERERA MF; JOYA CM; FUNES C; GONZÁLEZ V; CUENYA MI; CASTAGNARO AP

San Miguel de Tucumán

Congreso; XXX ISSCT Congress; 2019

Sugarcane brown rust is one of the main diseases affecting sugarcane and Pucciniamelanocephala Syd. & P. Syd., its causal agent, has been reported as one of the mosteconomically important fungal pathogens worldwide. For that reason, the knowledge of itsgenetic diversity should be considered when developing resistance breeding strategies. Theaim of this study was to estimate the genetic diversity of P. melanocephala in the sugarcanegrowing area of Tucumán, Argentina, using a reproducible molecular technique. 137 leafsamples with brown rust symptoms were collected during 2011, 2012 and 2013 seasons in 40locations in Tucumán from 33 sugarcane genotypes. Samples were obtained by harvestingurediniospores from pustules with a brush and total DNA extraction was optimized. Sampleswere characterized by AFLP markers and eight of them corresponding to different clustersaccording to AFLP analysis were also characterized by seven SSR primer pairs. Only 73 out of137 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 ofpolymorphism detected indicated high pathogen diversity where no apparent correlationbetween P. melanocephala samples and sugarcane genotype, location sampled, or year ofcollection 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 matrixesobtained with AFLP and SSR markers. Results revealed that both AFLP and SSR were usefulto examine the molecular polymorphism of P. melanocephala samples and might have asignificant contribution to the knowledge of its genetic diversity. Due to the high level ofpolymorphism detected in P. melanocephala in Tucumán Province, breeders should be alert asthe durability of the resistance could be continuously threatened.