Identification Of Viruses On Kiwifruit And Moleculelar Variability Of Kiwifruit Viruses In Shaanxi Province

Actinidia is an important cash crop in the world.In 2017,the output of kiwifruit was2.025 million tons,and the planting area was 16.7 million hectares in China,the planting area and output ranked first in the world.Shaanxi Province is the largest producer of kiwifruit in China.In 2017,planting area was 6.9 million hectares and the output of kiwifruit reached 1.389 million tons,which was more than 50% of China’s total production.In recent years,While the yield and planting area of kiwifruit in Shaanxi Province ranks first in the country,but there are few studies in the filed of kiwifruit virus disease.In order to figure out the species,incidence and molecular variation of kiwifruit virus in the main producing areas of kiwifruit in Shaanxi Province,from 2017 to 2018,we collected 440 kiwifruit samples suspected to be infected with viruses from Meixian,Zhouzhi,Yangling and Hanzhong in Shaanxi Province.Due to RT-PCR combined with Dot-ELISA,kiwifruit viruses were identified,viruliferous percent of the seedlings was counted,the nucleic acid sequence of the coat protein(CP)was cloned and the molecular variation was analyzed.The results were as follows:1.Six viruses were identified on kiwifruit,namely Actinidia virus A(Ac VA),Actinidia virus B(Ac VB),Actinidia chlorotic ringspot-associated virus(Ac CRa V),Cucumber mosaic virus(CMV),Apple stem grooving virus(ASGV),Potato virus X(PVX).To our knowledge,this is the first report of PVX infecting kiwifruits.And this is the first to detect CMV and PVX on kiwifruit in Shaanxi Province.2.The viruliferous percent of the seedling samples of the six viruses was counted.As to the single-virus infection,the highest was Ac CRa V of 41.6%,and the lowest was CMV of21.1%.Different viruses have different rates of viruliferous percent in different regions.The rates of Ac CRa V and ASGV in Meixian County were the highest,43.5% and 42.4%,respectively.The highest rates of Ac VA and Ac VB were 56.7% and 52.5%,respectively.In Yangling Ac VA and Ac VB,the highest of viruliferous percent were 85.7% and 71.4%respectively;in Hanzhong,the highest rate of Ac CRa V was 70.0%.Most of the kiwifruit viruses showed complex infection when infecting plants.Ac VA+Ac VB was the most common in different infection combinations,and the viruliferous percent in the samples reached 22.3%.3.Based on the nucleic acid sequences of six kiwifruit virus CP genes,phylogenetic trees were constructed.The results showed that the sequences of Ac VA,Ac VB and Ac CRa V were divided into groups I and II,and the molecular variation was larger.On the contrary,ASGV,CMV and PVX were almost allocated to the same group and the molecular variation was very small.