Prevalence and Distribution of Plant-Parasitic Nematodes Associated with Doum Palm Trees Hyphaene thebaica (L.) Mart. in Aswan Southern Egypt with Emphasis on Biochemical and Molecular Identification of Root-Knot Nematode

An intensive field study was carried out during the period from December, 27th 2016 to November, 3rd 2017 to survey nematode associations of doum palm trees, Hyphaene thebaica in Aswan governorate, Southern Egypt. In this regard, a total of 105 composite rhizosphere soil and root samples were collected from different provinces (Aswan, Daraw, Edfu and Kom Ombo) belonging to Aswan governorate. Nematodes were extracted by Cobb’s wet-sieving and centrifugal sugar flotation techniques and identified to the genus level according to the original body descriptions and standard identification keys of plant-parasitic nematodes. Fourteen genera were found to be associated with the rhizosphere of doum palms and could be descendly arranged based on their frequency of occurrence (FO%) as follows: Meloidogyne (46.7%), Rotylenchulus (33.3%), Helicotylenchus (27.6%), Aphelenchus (17.1%), Tylenchus (14.3%),Hemicriconemoides (12.4%), Tylenchorhynchus (9.5%), Ditylenchus (8.6%), Aphelenchoides (7.6%), Pratylenchus (6.7%), Trichodorus (5.7%), Criconemella (4.8%), Paratylenchus (3.8%) and Hoplolaimus (2.9%). It was clearly noticed that root-knot (Meloidogyne), reniform (Rotylenchulus) and spiral (Helicotylenchus) nematodes appeared to be the most prominent genera recording high prominence value (PV) reaching 3444, 2816 and 1902, respectively and population density (PD) 504, 488 and 362 nematodes/250 cc3 soil, consequently, whereas the rest genera were less prominent representing PV ranging between 109-595 with PD reaching 46-201 nematodes/250 cc3 soil. Examination of root samples revealed the presence of ideal root galling caused by Meloidogyne and their sedentary adult females were isolated and subjected to the traditional identification to the species level using perineal pattern test and reconfirmed by the biochemical and molecular identification methods. Meloiodogyne javanica appeared to be the predominant root-knot nematode species in this study. The current results updated the database of nematode associations with their plant hosts in Egypt and introduced doum palm as new host of M. javanica and probably to other nematodes.