Distribution and identification of root-knot nematodes in rice cultivated areas of Pathum Thani province, Thailand

Abstract

Root-knot nematodes, Meloidogyne spp., have been reported in rice production systems of many countries. High population densities of the nematodes in soil usually lead to yield losses of rice cultivation. Therefore, the objectives of this study were to survey the quantity and to identify the species of root-knot nematodes found in rice fields from six districts, including Nong Suea, Lam Luk Ka, Thanyaburi, Khlong Luang, Muang, and Sam Khok of Pathum Thani province. The perineal patterns of adult females of root-knot nematodes collected from all rice fields were generally oval shaped, without lateral lines, and smoothly cuticular, which matched with M. graminicola. Nematode populations in soil and in rice roots were determined by Christie and Perry technique and Extraction tray method, respectively. The results demonstrated that the highest nematode population present in soil was found in Muang District (8.3 nematodes/150 g soil) and in roots in Sam Khok District (70.6 nematodes/10 g roots) where Pathum Thani 1 rice cultivar was grown. The morphological characters of the second stage juveniles included the conoid tail shape and body and stylet lengths of 427–501 µm and 13–15 µm, respectively. Molecular identification based on the Polymerase Chain Reaction (PCR) with three different primer sets, including rDNA2/ rDNA1.58s, C₂F₃/1108 and SCAR-MgFW/SCAR-MgRev showed DNA fragment size of 490, 520 and 650 bp, respectively. Phylogenetic tree based on 18S-ITS1-5.8S genes reiterated that the root-knot nematodes found in this study were M. graminicola with 98% similarity to root-knot nematodes from rice fields of Vietnam. Thus, the main species of root-knot nematodes isolated from Pathum Thani’s rice fields were M. graminicola.