RESISTANCE OF DIPLOID TRITICEAE SPECIES AND ACCESSIONS TO THE COLUMBIA ROOT-KNOT NEMATODE, MELOIDOGYNE CHITWOODI

The Columbia root-knot nematode, Meloidogyne chitwoodi race 2, is asso ciated with several plant species, including members of the tribe Trit iceae. We evaluated lj diploid species for M. chitwoodi gall and repro ductive indices from the following genera: Agropyron, Pseudoroegneria, Hordeum, Psathyrostachys, and Thinopyrum. Species from the genus Thin opyrum (Thinopyrum bessarabicum; J genome) and Psathyrostachys (Psathy rostachys fragilis, P. juncea, P. stoloniformis; N genome) expressed m ore resistance to M. chitwoodi than species within the genera Agropyro n (Agropyron cristatum and A. mongolicum; P genome), Pseudoroegneria ( Pseudoroegneria spicata, P. stipifolia, A. aegilopoides, P. libanotica ; S genome), and Hordeum (Hordeum bogdanii, H. brevisubulatum, H. cali fornicum, and H. chilensis; H genome), although there was variation am ong individuals within P. spicata, P. juncea, and P. fragilis. The var iation among genera and within species indicates that it would be poss ible to select Triticeae grasses for resistance to M. chitwoodi in ord er to identify and introgress genes for resistance into cultivated cer eals.