RESPONSE TO ROOT-KNOT NEMATODES OF A GERMPLASM COLLECTION OF RED-CLOVER AND RELATED SPECIES

A germplasm collection of red clover (Trifolium pratense I,.) and seve n related species was evaluated in greenhouse tests for resistance to Meloidogyne arenaria (Neal) Chitwood, M. hapla Chitwood, M. incognita (Kofoid & White) Chitwood, and M. Javanica (Treub) Chitwood. Plants we re rated for root galling severity and nematode egg production at eigh t weeks after inoculation with 1500 nematode eggs. A resistance index, RI = root(gall(2) + egg(2)), was generated to assess the plants' reac tion to nematode infection as immune, highly resistant, resistant, mod erately resistant, intermediate, moderately susceptible, susceptible, or highly susceptible. More than 98% of red clover accessions were int ermediately to highly susceptible to all four root-knot nematode speci es. Only one accession, PI271627 introduced from India, had a moderate resistance level to the four nematodes tested. About one third of the T. medium accessions were resistant or highly resistant to M. arenari a, M. incognita, and M. javanica whereas more than 50% of the T. alpes tre accessions were highly resistant or immune to all four nematodes s pecies. Genetic factors for resistance to root-knot nematode could be introduced into T. pratense through interspecific hybridization with T . medium and/or T. alpestre.