Identification Of The Plant Parasitic Nematodes Of The Root And Tuber Crops And Morphological And Genetic Analysis On Different Populations Of Ditylenchus Destructor In Shanxi Province

Root and tuber crops are the dominant crop and play important roles during the adjustment period of agricultural structure in Shanxi Province.Plant diseases damaged by plant parasitic nematode are an important factor for economical outputs of root and tuber crops.In this study,264 samples were collected from the tuber and the rhizosphere soil of the root and tuber crops in 9 cities,17 counties or districts in Shanxi Province.Major plant parasitic nematodes were identified by traditional classification and molecular methods.Morphological characters and ITS sequence diversity of dominant species Ditylenchus destructor from different geographical populations were studied.In addition,distribution of plant parasitic nematodes and symptoms on tubers were analyzed.The main results are as following:1.Nine species in eight genera of plant parasitic nematodes were identified using morphological characters,SSU?LSU D2/D3 and ITS r DNA molecular characteristics and phylogenetic relationships.They are: Aphelenchus avenae,Geocenamus sp.,Heterodera glycines,Pratylenchus coffeae,Pratylenchus scribneri,Psilenchus hilarulus,Rotylenchus capensis,Tylenchorhynchus sp.and Ditylenchus destructor.Rotylenchus capensis is a new record in China.Pratylenchus scribneri and A.avenae were found firstly on potato tubers in China.Pratylenchus coffeae was found firstly in Dioscorea opposita tuber in Shanxi Province.Psilenchus hilarulus is a new record in Shanxi Province and H.glycines were found firstly under rhizosphere soil of potato in Shanxi Province.2.Ditylenchus destructor was the dominant species in the plant parasitic nematode and 10 populations were found in the tuber and under the rhizosphere soil of three crops from five cities in Shanxi Province.Morphological characteristics contrast of ten populations showed that there is no differentiation in the morphological characteristics,but there is differentiation in morphometrics of body length,stylet length,tail length and de Man's a,b,c,V and T values.ITS sequence characteristics and phylogenetic analysis of ten populations showed that there are two types ITS populations: type A and type B,type A is the dominant population and has a wide distribution.In addition,there is no significant differentiation in the geographical and host distribution for ten populations of D.destructor in Shanxi Province.3.The distribution statistics showed that plant parasitic nematodes were found in seven cities,including Datong City,Xinzhou City,Taiyuan City,Jinzhong City,Linfen City,Yuncheng City and Changzhi City,but there is no found in Lvliang City and Shuozhou City.The abundance of plant nematodes species ranked as north Shanxi >middle Shanxi > south Shanxi.The hosts of plant parasitic nematodes include sweet potato(D.esculenta),potato(Solanum tuberosum)and yam(D.opposita).The abundance of plant nematodes species ranked as potato > yam > sweet potato.The extraction ratio of plant parasitic nematodes is 54.5% and ratio extracted from soil(70.0%)higher than tubers(45.1%).In addition,D.destructor has a wide distribution and mainly in middle and south of Shanxi Province,but it was no found in north Shanxi.Type B population was only found from potato tuber in Pu County,Linfen City,and other nine populations were all type A.The extraction ratio and population density was highest from sweet potato tuber.The damage degree of D.destructor ranked as sweet potato > potato > yam.