Observation Of Biological Characteristic And Evaluation Of Resistance To Powdery Mildew Of RPW8.2 Transgenic Grapevine

Widely cultivated grapevine(Vitis vinifera L.)in the world is sensitive to pathogen,especially sensitive to powdery mildew caused by Erysiphe necator.The use of genetic engineering technology to improve the disease resistance of grapes is one of the important directions of grape molecular breeding.In the previous study we transferred the broad-spectrum gene RPW8.2 to the disease-susceptible grape ‘Thompson Seedless’,and inoculated powdery mildew in the phytotron,the results indicated that transgenic grape increased the resistance to the powdery mildew.Based on the previous study,the transgenic grapes were transferred to plastic greenhouses,observed the growth characteristics of transgenic grapes,and further tested their resistance to powdery mildew.The main results are as follows:1.The expression of RPW8.2 gene in transgenic ‘Thompson Seedless’ grape did not affect the biological characteristics of the plants: the difference between the phenophase of the transgenic and wild-type plants was controlled within 5 days;the difference of shoot elongation within two weeks was controlled about 4 cm.2.The cutting seedlings and isolated leaves were inoculated with En.NAFU1,which was inoculated in the greenhouse for 7 days.After 3,5,7,and 14 days of inoculation in a light growth chamber,trypan blue staining was used to observe hypha growth.The results showed that the length of hypha and the number of spores of the powdery mildew in the wild type grapes were more than twice that of the transgenic plants,and the haustorium growed well.But there was a phenomenon of poor development of the haustorium and darkening color in the transgenic plants.The growth of the powdery mildew hyphae in the transgenic plants was inhibited,and the resistance of the transgenic grape to the En.NAFU1 was higher than that of the wild type plants.3.After 15 days of natural infection with the powdery mildew,the transgenic grape was stained with trypan blue and DAB and the spore number was counted.The results showed that the amount of spores on the leaves of the transgenic plants was 35% of the wild-type plants,whereas the accumulation of hydrogen peroxide on the wild-type plants was only 20% of the transgenic plants.This indicates that the transgenic grape is able to inhibit the growth of powdery mildew by accumulating a large amount of hydrogen peroxide,which is consistent with the results of indoor inoculation of transgenic Arabidopsis and transgenic grapes.4.In the case of natural susceptibility,the wild type ‘Thompson Seedless’ grape was evaluated for disease resistance.Its disease index was 32.85,and the disease resistance level was 4,indicated it is a susceptible type.The susceptibility index of transgenic grapes ranged from 3 to 21,and the disease resistance levels were grade 2 and 3.This shows that the transgenic grapes are more resistant to the powdery mildew than the wild type plants under natural disease conditions.