Biological Characteristics And Population Diversity Of Peanut Stem Nematode Ditylenchus Arachis

Ditylenchus arachis was a new species of stem nematode parasitizing peanut in China which was first described in 2014.Surveys for distributions of D.arachis have been conducted in major peanut production regions of Shandong and Hebei Provinces.Morphology characteristics and genetic diversities for populations of D.arachis have been studied.The biological characteristics of D.arachis were also studied in the paper.The main results were as follows:1.The result of the investigation has showed that D.arachis were widely distributed in peanut production areas in Shandong and Hebei Province.Based on the sampels collected in peanut fileds or sends by local famers,the results have showed D.arachis were distributed in 18 peanut produced areas of 7 counties in Shandong and Hebei provinces.It was also found for the first time that the stem nematode was distributed in Henan provinced.The results provided a theoretical basis for prevention and control of peanut stem nematode disease.2.The morphological characteristics of ten populations of D.arachis in Shandong,Hebei,Henan provinces have been examined,and the results have been showed that a few morphology variation of D.arachis have been found among the 10 populations,but characteristics of morphological classification were accorded with that of original descriptions of D.arachis species.3.Molecular characteristics of the geographical populations of D.arachis have been determined.The region of rDNA-ITS and 28S D2-D3 of the 10 populations of D.arachis have been sequenced and analysed.The results have showed that sequence similarities among the 10 populations and same region sequences deposited in GenBank for the D.arachis were 99%-100%and indicated that no genotype existed in the geographic populations of D.arachis in the up 3 provinces.The results of the phylogenetic analysis based on rDNA-ITS region and D2-D3 expansion of 28S rDAN showed that the ten populations were placed in same independent clade with populations of D.arachis deposited in GenBank,and separated from the other clade of sister group of D.destructor.The results of network with software TCS 1.21 showed that there may be existed few differences in the species because of the diversity of the ancestral population or the long-term geographical isolation.4.The biological characteristics of D.arachis were studied.The results of inoculation experiments have showed that all juvenile stage except first stage of juvenile and adult of D.arachis could infect the root of peanut seedlings.The infection experiment using Pluronic F-127 confirmed that D.arachis could infect whole peanut roots,and most of invade sites of root by the nematode were on the other part of the roots,rather than root tips.For the first time the inocultion experiments have showed that infection of D.arachis could depress growth of peanut,reduced the number of peanut nodule,reduce yields and quality of peanut.The experimental results showed that embryonic development time of D.arachis was about 5 days and whole life history was 15-20 days at 26?.D.arachis couldn't be parthenogenetic,but only gamogenetic.