Histological Study,Virus Movement And Detection In Vitro Micrografts Of Grapevine

Grapevine(Vitis)is one of the economically important fruit crops in the world as well as in China.Grapevine leafroll disease(GLRD),which widely occurs in all grapevine-growing regions of the world and is also prevalent in China is one of the most serious viral diseases affecting the yield and quality of grape,Grapevine leafroll-associated virus-3(GLRa V-3)is a major agent causing GLRD.Previous studies have shown that GLRaV-3 reduces vine growth vigour,depresses photosynthesis,resulting in low yield and poor quality of grapevine berries.Availability of virus detection techniques is necessary for production of virus-free plants and quarantine inspection.The most common methods include enzyme linked immunosorbent assay(ELISA),reverse transcription polymerase chain reaction(RT-PCR)and biological indexing plant,with the latest one being the most effective and reliable method for the detection of grapevine leafroll disease.In this study,in vitro healthy and GLRaV-3-infected ‘Cabernet Sauvignon' and virus-infected of ‘HuNan-1' and ‘Chardonnay' were used as scions and rootstocks for micrografting.Histological observations and virus movement were studied in micrografting combinations of healthy/ infected and infected/healthy micrografts.The main results are as follows:1.In healthy/infected micrografting combination,earlier bud break and faster growth were found in scions of micrografts.After 3 days of micrografting,callus started to initiate and after 7 days,the callus was obviously observed,but no virus infection was detected in the healthy scions.After 14 days of micrografting,vascular connection was observed between the healthy scions and virus-infected rootstocks,and virus infection of about 53% was detected in the healthy scions.After 21 days of micrografting,vascular connection was completely between the healthy scions and virus-infected rootstock,and at this time,100% of the healthy scions were detected to be virus infected.2.Infected/healthy micrografting combination,earlier bud break and in greater fresh weight of roots were found in the rootstocks.Histological patterns were similar to those observed in healthy/infected micrografting combination.However,about virus-infected rate was 36.7% and 100% of virus infection rates were detected in the healthy scions after 14 and 21 days of micrografting These data show virus movement was faster from the infected scions to the healthy rootstocks than from the infected rootstocks to the healthy scions.3.In stress medium,the content of virus and gene expression of controlling anthocyanins synthetic is the positive correlation relationship on the white grapevine infected GLRaV-3.To the best of our knowledge,this is the first report addressing histological process of micrograft development and virus localization in micrografts at different stages of micrografting.In vitro culture system established in this study facilitates studies on the ‘pure' impact of the viral infection on micrografting.