PLANT-PARASITIC NEMATODES ASSOCIATED WITH YAMS (DIOSCOREA SPP.) AND IDENTIFICATION OF MELOIDOGYNE AND PRATYLENCHUS SPECIES IN THREE YAM-GROWING REGIONS OF COSTA RICA

Abstract

Yam (Dioscorea spp.) and yampee (D. trifida) tubers showing symptoms of dry rot and galls have been observed frequently in storage facilities and yam fields from the North, Atlantic, and South (Brunca) regions of Costa Rica. A survey of plant-parasitic nematodes associated with yams and yampee was performed in these three regions. The analyses showed that the most frequent nematodes in tubers were Scutellonema and Aphelenchoides (50% of the samples), followed by Meloidogyne (47%), Tylenchus (43%), Pratylenchus (33%), and Helicotylenchus (23%). Female perineal patterns and molecular techniques such as PCR-RFLP and PCR with species-specific primers were used to identify Meloidogyne species. Meloidogyne javanica and M. incognita were found concomitantly in white yam (D. rotundata) and M. incognita in three yampee samples. Species-specific primers for Pratylenchus species allowed the identification of P. coffeae and P. brachyurus in both yellow yam (D. cayenensis) and yampee. Pratylenchus coffee was found in the three regions of Costa Rica. Furthermore, P. coffeae and P. brachyurus were also found concomitantly in two samples. A Bayesian analysis based on the D2-D3 region of the 28S gene placed one population extracted from greater yam (D. alata) and one from yampee in clades with P. zeae and P. gutierrezi, respectively. The present study is the first report of Meloidogyne and Pratylenchus species in yams and yampee in the major yam production areas of Costa Rica using fast and accurate molecular methods.