Species Identification Of Parasitic Nematode Of Pitaya In Fujian Province

Industry of pitaya(Hylocereus undatus)has been developing rapidly and has become an important cash crop for poverty alleviation in rural areas.In recent years,yellowing and decline disease occurred commonly in pitaya planting areas.During 2019,to identify the species,distribution and damage of pathogen nematodes,the author collected 115 samples of roots and rhizosphere soils from 11 bases in the main planting areas of pitaya including Fuzhou,Quanzhou,Zhangzhou in Fujian province.Below are key research findings:The species of pitaya root-knot nematodes infecting pitaya: Pitaya root-knot nematode diseases occured in the pitaya planting areas of Zhangzhou and Quanzhou in the southern of Fujian province.The rootknot nematodes were isolated from pitaya roots and identified,the morphological characteristics from second-stage juveniles and perineal patterns from adult females matched the original description of Meloidogyne incongnita and M.enterolobii in Zhangzhou region and Quanzhou region respectively.Species identity were further explored by sequencing the r DNA-ITS1-5.8S-ITS2 region,28S-D2D3 region,mt DNACOII region,and NAD5 region,and by phylogenetic trees derived from Maximum Likelihood and Bayesian analysis based on the above genes.The two pathogenic nematode species were identified as M.incognita and M.enterolobii respectively.Species identification were further confirmed with M.incognita or M.enterolobii specific primers Mi-F/Mi-R or MeF/Me-R.The pot inoculation experiments have confirmed pathogenicity of M.incognita and M.enterolobii on pitaya.The surveys have shown that root-knot nematodes are the most important nematode of pitaya in Fujian province,but only been founded in south Fujian.This is the first record of M.enterolobii parasitizing pitaya in mainland of China,and first report of M.incognita infecting pitaya in Fujian province.M.enterolobii is an important pathogenic nematodes with international concern in recent years wiht widely hosts,highly pathogenic.M.enterolobii has been found in several crops and fruit trees in southern Fujian,and should be given sufficient attention to prevent spread.The species of other plant pathogenic nematodes in the rhizosphere of pitaya: Based on the methods of morphology and molecular biology(r DNA-ITS1-5.8S-ITS2 region and r DNA-28S-D2D3region),the isolated species of pitaya rhizosphere nematodes were identified.There are 6 species of nematodes,which are marked as Xiphinema insigne,X.elongatum,Tylenchorhynchus annulatus,T.leviterminalis,Rotylenchulus reniformis and Helicotylenchus dihystera.Among them,T.annulatus and H.dihystera were the dominant populations,which isolation frequency was 73% and 64%.Respectively,it is the first report that X.insigne and X.elongatum were found on pitaya.