PHYTOPARASITIC NEMATODES ASSOCIATED WITH ORNAMENTAL PLANTS IN RIYADH REGION, CENTRAL SAUDI ARABIA

A survey of phytoparasitic nematode genera was conducted in the rhizosphere of 55 ornamental plants (herbaceous, trees and shrubs) in Riyadh region, central Saudi Arabia from February 1999 to June 2001. A total of 453 soil and room samples were collected, and 200 cm3 soil subsamples were assayed for nematodes. A variety of twenty phytoparasitic nematode genera were extracted and identified from the rhizosphere of surveyed plants in general. These genera is a descending order of frequency were; Helicotylenchus (43.7%), Tuylenchorhyachus (41.1%), Meloidogyne (37.1%), Aphelenchus (24.9%), Tylenchus (24.3%), Rotylenchulus (21.4%), Criconemella (20.5%), Heniericonenioides (11.7%), Aphelenchoides (6.6%), Ditylenchus (5.7%), Paratrichodorus (5.5%), Pratylenchus (4.9%), hoplolamus (4.2%), Trichodorus (3.3%), Xiphinema (3.9%), Longidarus (1.8%), Hemicycliophora and Paratylenchus (0.9% each), Rotylenchus (0.7%) and Psilenchus (0.2%). Most of nematode genera were present at population densities of 10-100 nematodes /100cm3 soil, but a relatively high population densities were found with Parylenchus on Codiaeum varigatum, Meloidogyte javanica on Rosmarinus officinalis and Helicotylenchus on Matthiola incona (3442, 1528 and 1366 nematodes /100 cm3 soil, respectively). According to the prominence value (PV), the most prominent nematodes in general were; Parvatylenchus, Helicotylenchus, Meloidogyne, Rotylenchulus and Criconemella. Meloidogyne javanica was identified from galled herbaceous ornamental plants and 15 ornamental trees and shrubs, whereas M. arenaria was only identified from galled roots of Dahlia variabilis and Clerodendron inerme. This is the first extensive survey of phytonenatodes associated with ornamental plants in Saudi Arabia including many new host records (especially for root-knot nematodes) in the country