Molecular diagnostics of Puccinia melanocephala and Puccinia kuehnii causing agents of brown rust and orange rust, respectively and evaluation of rust resistance in the EEAOC germplasm collection using molecular markers associated to Bru1 a broad-range re

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

Sugar Tech

Sugar Tech

Año: 2016

Brown rust (Puccinia melanocephala) and11 orange rust (P. kuehnii) cause important yield loss in global12 sugarcane production. Due to the difficulties of distin-13 guishing between the two diseases to the naked eye, it is14 essential to use molecular techniques for an accurate rust15 diagnosis. A major gene, Bru1, which confers resistance to16 a broad spectrum of P. melanocephala strains in different17 parts of the world, has been described, and molecular18 markers closely associated with this allele have been19 developed. The aims of the present study were: (1) to20 optimise a PCR-based method to diagnose and characterise21 the causal agent of both rusts in Tucuma´n; (2) to determine22 the usefulness of the Bru1 gene in the Sugarcane Breeding23 Program of ??Estacio´n Experimental Agroindustrial Obispo24 Colombres?? (EEAOC) by studying its association with25 resistant and susceptible phenotypes; and (3) to assess the26 frequency of the Bru1 allele in the sugarcane germplasm of27 the EEAOC. Conditions for both rust diagnoses were28 optimised. Out of 129 genotypes evaluated to study the29 usefulness of the Bru1 allele, 49 were found to be resistant30 to brown rust, but only eight of these resistant genotypes31 were positive for the Bru1 allele. Also frequency of32 appearance of the Bru1 allele was analysed in 191sugarcane accessions of the EEAOC germplasm, and its 33presence was detected in only 7 % of the genotypes eval- 34uated. In conclusion, although results show that Bru1 35markers enable positive selection of this character, addi- 36tional source(s) of resistance are available in the EEAOC 37Sugarcane Breeding Program.