SPATIAL DISTRIBUTION OF <I>MELOIDOGYNE</I> SPECIES AND RACES IN THE TOMATO (<I>LYCOPERSICON ESCULENTUM</I> MILL.) PRODUCING REGION OF MORELOS, MEXICO

Abstract

Guzman-Plazola, R. A., J. Jaraba N., E. Caswell-Chen, E. Zavaleta-Mejia, and I. Cid del Prado V. 2006. Spatial distribution of Meloidogyne species and races in the tomato (Lycopersicon esculentum Mill.) producing region of Morelos, Mexico. Nematropica 36:215-229. Regional spatial patterns of Meloidogyne species and races infecting tomato crops in Morelos state were analyzed from 50 tomato fields in the municipalities of Atlatlahucan, Tlayacapan, Totolapan and Yecapixtla. Rhizosphere soil was collected at each site and evaluated for soil texture, organic matter content, pH and electrical conductivity. Soil collected at each site was distributed in five 2-liter plastic pots. Four tomato seedlings cv. Rio Grande were planted in each pot. Ten to 20 egg masses per positive site were extracted and individual egg masses were placed in the root zone of an individual tomato plant of the same variety. Galling of each was assessed by the Taylor and Sasser Root Gall index. Fourteen out of fifty tomato fields contained Meloidogyne spp., but isolates from only eight fields were able to reproduce on tomato cv. Rio Grande. Thirty three isolates from all sites were identified to species using morphological and morphometric parameters. Species and races from twenty one of those isolates found in the region were: Meloidogyne incognita race 1, M. arenaria race 2 and M. javanica race 1 based on North Carolina Differential Host Test. At the regional level, Meloidogyne spp. were found distributed in three areas. Soils positive for Meloidogyne were moderately to slightly acid, and most of them had 38 to 71% sand and 13 to 29% clay content Soil organic matter content and pH were highly correlated with principal components I and II, respectively. This correlation allowed us to classify soils from all the sampled sites into four groups of edaphic similarity. Conduciveness of soils to Meloidogyne was assessed by means of a logistic regression model of Meloidogyne presence versus sand and clay content. Sand and clay content were useful to forecast the conduciveness of Meloidogyne spp. in the tomato producing soils of Morelos.