Diversity of root-lesion nematodes (Pratylenchus spp.) associated with wheat (Triticum aestivum and T. durum) in Morocco

Abstract

Root-lesion nematodes (Pratylenchus) have a worldwide distribution and cause severe production constraints on numerous important crops. During a survey of the wheat-growing area of Morocco, 17 populations of root-lesion nematode were collected. They were identified on the basis of their morphological and morphometric characters, and by molecular methods. Microscopic observations of females and males demonstrated the occurrence ofP. penetransin 13 of the 17 samples;P. thorneiandP. pseudocoffeaewere detected in four samples from Zaers and a single sample from Settat, respectively. A duplex PCR primer set was used to confirm the presence ofP. penetranswhile the species-specific forward primer PTHO and the common reverse primer D3B were used forP. thornei. For the remaining populations, the D2-D3 expansion segments of the 28S rRNA gene were amplified and the obtained sequences were compared with those ofPratylenchusspecies in the GenBank database. This comparison confirmed the morphological identifications and revealed a population ofP. pinguicaudatus. The study of the phylogenetic relationship of the MoroccanPratylenchuspopulations showed a high similarity (99-100%) between allP. penetranspopulations. The population dynamics of sixPratylenchuspopulations from Morocco were evaluated on carrot disk cultures at 4, 8 and 12 weeks after inoculation, and at 10, 15, 20 and 25°C. The optimum temperature for reproduction of all populations was 20°C. After 8 weeks at this temperature, nematode numbers increased up to 458-fold, 310-fold and 252-fold for the four populations ofP. penetrans, theP. thorneiand theP. pseudocoffeaepopulation, respectively.