Identification of field populations of Meloidogyne spp. by chromosome number.

Identification of species of Meloidogyne Goeldi, 1887 is fi-equently accomplished by using perineal patterns and morphometrics, but intraspecific populations are not easily distinguished. Chromosome numbers have been determined for 10 (6) of the 36 species of Meloidogyne which are currently recognized (1, 5). Four of these species have a range of chromosome numbers. This chromosome range permits the identification of 19 chromosomal populations among M. arenaria (Neal, 1889) Chitwood, 1949; M. hapla Chitwood, 1949; M. incognita (Kofoid and White, 1919) Chitwood, 1949; and M. javanica (Treub, 1885) Chitwood, 1949. The purpose of this study was to identify Meloidogyne spp. present in 0.2 ha of a 37-year-old vineyard of own-rooted grape vines (Vitis vinifera L., 'Thompson Seedless') on McCall Avenue, Selma, California. The use of perineal patterns alone to identify species of Meloidogyne was unsatisfactory for an analysis of nematode community structure (3, 4). Soil samples were taken from the root zones of six vines chosen at random from 200 vines. Forty samples were taken from each vine site with a 7.5-cm diam auger (3). These 240 soil samples (Hanford sandy loam: 54.6% sand, 27.5% silt, 17.9% clay) were pooled. Eight tomato plants (Lycopersicon esculentum L., 'Pearson') were grown in subsamples of this vineyard soil. Sixty single egg-mass cultures were established on 'Pearson' tomato in the greenhouse. The females which produced these egg masses were dissected from rootgall tissue. Chromosome analyses were performed on these females according to the method of Tr iantaphyl lou (7), and perineal patterns were cut from the empty cuticles. After 6 weeks, each culture was