Occurrence,Distribution And Infection Characteristics Of Cyst-forming Nematodes And Plant Parasitic Nematodes Associated With Wheat In Shanxi,China

Wheat is one of the most important food grain source for human beings.Plenty of plant nematodes can parasitize wheat and causes yield reduction,in which cyst-forming nematode is one of the most important,widely distributed sedentary endoparasitic nematode group.During 2015-2017,a systematic study was conducted in the south regions of Shanxi Province to identify cyst-forming nematodes and associated plant parasitic nematodes in the rhizosphere of wheat.The main results were as follows:1.Species and distribution of cyst-forming nematodes in wheat from shanxi,China A systematic survey on cyst-forming nematodes distribution in Pinglu、Ruicheng、Wenxi、Xiaxian、Yanhu and Yongji of Yuncheng city,Shanxi province were couducted during 2015-2017.It showed that 55% incidence of cyst-forming nematodes was detected in the samplings of wheat in Yuncheng,which was found increased as compared to previous years.No cyst-forming nematode was found in the sampling from Pinglu.The average density of white female differs between each district depending on cultivation system and soil texture.The highest average density of white females was 53 females / 100 m L soil in Yanhu district of Yuncheng and the highest population density reached to 101 females/100 m L soil.Based on the morphological characters,morphometrics,PCR amplification and sequences of r DNA-ITS and mt DNA-COI gene,all the cyst-forming nematodes populations detected in Shanxi were identified as Heterodera avenae(cereal cyst nematode,CCN).While H.filipjevi,one of the most important cyst-forming nematodes in China,was not detected during this survey.2.Infection and development of CCN in wheat growing area of Shanxi In order to confirm the life cycle of CCN in the wheat fields of Shanxi,during the growing season of 2015-2016 and 2016-2017,systematic observations on the infection and development of CCN in 2 wheat field of Yuncheng,Gunan Village of Yanhu and Xihan village of Wenxi,were made,respectively.It was found that CCN population has only one generation during the growing season.A few hatching and infection of second stage juveniles(J2s)were observed in December and more hatching and infection of J2 s were observed in early March.The peak of hatching occurred in the early and middle March.The infection of J2 s occurred in the late March.Third stage juveniles(J3s)were observed in roots by late March,and the development peak of J3 s were observed in middle of April.Fourth stage juveniles(J4s)were first found in roots by late April and the development peak occurred in early May.White cysts of CCN were observed on the wheat roots by naked-eyes in late April,and the development peak of white cysts were in middle and late May.The related results would be useful for proper integrated management of CCN in Shanxi province.3.Other major plant parasitic nematodes associated with wheat in Shanxi Based on the morphological observation,morphometrics and molecular methods,4 plant parasitic nematode species belong to 4 different families were identified and described from the wheat growing areas of Shanxi,i.e.Pratylenchus neglectus(family Pratylenchidae),Helicotylenchus pseudorobustus(family Hoplolaimidae),Merlinius brevidens(family Dolichodoridae)and Filenchus vulgaris(family Tylenchidae).All the 4 species are new record found in the rhizosphere of wheat in Shanxi.P.neglectus and M.brevidens are the dominant speices in the wheat fields of Shanxi.In addition,the ultrastructure of the 4 species,observed with SEM,were provided,which will be useful for morphological identification of the related species.