Molecular Identification And Detection Of Lucerne Witches' Broom And Mosaic Disease In Xinjiang

Lucerne(Medicago sp.) is widely grown in the Xinjiang region, not only rich in nutritional value but also palatability, It can regard as important feed for livestock production. But in recent years, the survey found that lucerne field “arbuscular”, “mosaic” symptoms of the disease were widespread. The diseases affected the yield and quality of lucerne seriously, caused serious damage to livestock. In this study, molecular biology techniques were used to detect and identify lucerne witches and the mosaic disease. The main findings are as follows:1. Total DNA were extracted from 193 lucerne samples that showing arbuscular symptoms by using the nested-PCR with R16 m F2/R16 m R1 and R16F2/R16R2 universal primers, 23 samples of Xinjiang were obtained 1.2 kb specific fragment, the detection rate of 16.8%, thereby determined that the disease was phytoplasma. Then the phylogenetic tree showed that this phytoplasma strain is one of the members of 16Sr?-B subgroup, and appeared highest homology(99.3%) with euonymus whitening phytoplasma of them.2. Total RNA were extracted from 109 lucerne samples that showing mosaic symptoms by using the RT-PCR with specific primers that has been reported in the literature and detected to AMV, SMV, CMV, BCMV, TMV. Three pairs of primers which designed by three components of AMV genome could amplified 700 bp, 800 bp and 810 bp specific fragments by RT-PCR. After cloning and sequence alignment, determined pathogen of the lucerne mosaic disease is AMV. The result of the phylogenetic tree showed that the AMV and other ten strains of AMV were clustered into a large group, belong to AMV?group. Other primers could not amplified the specific fragments by RT-PCR, which means that did not detect SMV, CMV, BCMV and TMV. This study did not find compound infection.3. This is the first research that using the molecular biological techniques to determine the lucerne showing arbuscular symptoms is lucerne witches' broom, the lucerne showing mosaic symptoms is lucerne mosaic virus disease in Xinjiang, and determine the pathogen of two lucerne disease's classified taxonomic status. The results provide a theoretical basis for early diagnosis and detection of lucerne witches' broom and lucerne mosaic disease.