Molecular diagnostic of both brown and orange sugarcane rust and evaluation of sugarcane brown rust resistance in Tucumán- Argentina using molecular markers associated to Bru1, a broad-range resistance allele

RACEDO J.; PERERA M.F.; BERTANI R.; FUNES C., GONZÁLEZ V.; CUENYA M. I.; D´HONT A.; WELIN B. AND CASTAGNARO, A. P

REVISTA INDUSTRIAL Y AGRíCOLA DE TUCUMáN

Estación Experimental Agroindustrial Obispo Colombres

Año: 2014

Brown rust (Puccinia melanocephala), first reported in Tucumán in1988, and orange rust (P. kuehnii), not yet reported in Argentina, causeimportant yield losses in global sugarcane production. Due to the difficultiesin distinguishing these two sugarcane diseases with the naked eye, it isessential to use molecular techniques for an accurate diagnosis. A major gene, Bru1,which confers resistance to a broad spectrum of P. melanocephala strainsin different parts of the world, has been described, and molecular markersclosely associated with this allele have been developed. The present study aimsto i) optimise a PCR-based method to diagnose and characterise the causal agentpopulation of both types of rust in Tucumán; ii) determine the usefulness ofthe Bru1 gene in the Sugarcane Breeding Program of Estación ExperimentalAgroindustrial Obispo Colombres (EEAOC), by studying its association withresistant and susceptible phenotypes; and iii) assess the frequency of the Bru1allele in EEAOC sugarcane germplasm. Conditions for both brown and orange rustdiagnosis were optimised. When analysing 30 sugarcane samples showing rustsymptoms, only P. melanocephala DNA was amplified. Sugarcane varietiesfrequently used in the EEAOC Breeding Program were analysed in order to studythe usefulness of the Bru1 allele to diagnose brown rust resistance inTucumán. Out of 129 evaluated genotypes, 49 (38.0%) were found to be resistantto brown rust, but only 8 (16.3%) of these were positive for the Bru1allele. We then analysed the frequency of appearance of the Bru1 alleleby using diagnostic markers R12H16 and 9020-F4-RsaI, in 191 sugarcaneaccessions of the EEAOC germplasm. Presence, as determined by the two markers,was detected in only 7% of the evaluated genotypes. In conclusion, althoughresults showed that Bru1 markers enable positive selection of thischaracter, additional resistance source(s) are available in the EEAOC SugarcaneBreeding Program.