Identification and application of RAPD markers for anthracnose resistance in water yam (Dioscorea alata)

摘要

Anthracnose, caused by Colletotrichum gloeosporioides, is the most severe foliar disease of water yam (Dioscorea alata) worldwide. The tetraploid breeding line, TDa 95/00328, is a source of dominant genetic resistance to the moderately virulent fast growing salmon (FGS) strain of C. gloeosporioides. Bulked segregant analysis was used to search for random amplified polymorphic DNA (RAPD) markers linked to anthracnose resistance in F-1 progeny derived from a cross between TDa 95/00328 and the susceptible male parent, TDa 95-310. Two hundred and eighty decamer primers were screened using bulks obtained from pooled DNA of individuals comprising each extreme of the disease phenotype distribution. A single locus that contributes to anthracnose resistance in TDa 95/00328 was identified and tentatively named Dcg-1. We found two RAPD markers closely linked in coupling phase with Dcg-1, named OP17(1700) and OPE6(950), both of which were mapped on the same linkage group. OP17(1700) appeared tightly linked to the Dcg-1 locus; it was present in all the 58 resistant F-1 individuals and absent in all but one of the 13 susceptible genotypes (genetic distance of 2.3 cM). OPE6(950) was present in 56 of the 58 resistant progeny and only one susceptible F-1 plant showed this marker (6.8 cM). Both markers successfully identified Dcg-1 in resistant D. alata genotypes among 34 breeding lines, indicating their potential for use in marker-assisted selection. OP17(1700) and OPE6(950) are the first DNA markers for yam anthracnose resistance. The use of molecular markers presents a valuable strategy for selection and pyramiding of anthracnose resistance genes in yam improvement.