Identification and evaluation of resistance to white rot in grape resources

Abstract:【Objective】Grape is one of the most important fruit crops. Vitis vinifera is widely grown because of its high fruit quality and its capacity to grow in a wide range of climatic conditions. However, V. inifera is susceptible to many pathogens such as phytoplasmas, viruses, bacteria, and fungi. White-rot (Coniothyrium diplodiella) is a severe disease to V. vinifera cultivars in warm and humid climates in China, causing great loss of fruit production. It is extremely important to select new varieties of grape resistant to white rot. Digging germplasm with resistance is prerequisite for breeding new cultivar. The aim of this study was to identify and evaluate the resistance of grape germplasms and reveal the mechanism of resistance of grape plants.【Methods】The identification and evaluation of the resistance of Vitis species and hybrids were made using inoculation of pathogen in vitro. The transcription factor WRKY was used as indicating gene to detect the different resistance models of the resistant and susceptible resources.【Results】78 strains of 20 Vitis species were evaluated in vitro. V. davidii Ciputao was the most resistant resources to white rot. Resistance of different permplasms to C. diplodiella varied widely. Among the Chinese grapevines tested, no species was immune to the disease. Ciputao and Ciputao♀ exhibited strong resistance to the disease, while Guangximao, Jiuligousangye, Sangye 943, Sangye 946, Sangye 1099, Shuangxixianzhi 01, Shuangxixianzhi 03, Duolieyeyingyu, Qingyaoshanyingyu, Huadong 1058, Huajia 8, and Lingbaoq-♂♂iu were highly susceptible. European grapes were less resistant than the Chinese wildgrapes. There wereno highly resistant species (resistance rating II) in European grapes.‘Red Globe'‘Manicure Finger'‘Olympia'‘Fenghuang 51'‘Khoussaine Blanc'‘Munage'‘Amilia'‘Pinot Noir'and‘Ribier'were verysusceptible to the disease. American and Seibel grapevines varied in resistance from Ⅲ to IV, belonging tomoderately resistant to moderately susceptible species, Ciputao was the most resistant species and thuswas singled out for further investigation. After inoculation with C. diplodiella, the expressions of WRKY, PR, NPR1 were significantly different between the susceptible and the resistant grapevines. WRKY1, 2, 3, 11, and 70 were up-regulated and WRKY32 were down-regulated in‘Manicure Finger'. In Ciputao, WRKY1 and WRKY32 was down-regulated, WRKY2, 3, 11, and 70 were up-regulated, and the expressionof WRKY1 was unchanged. WRKY1 and WRKY32 were differentially expressed in Ciputao and‘Mani-cure Finger'. The expressions of PR1, PR2, NPR1 were scaled 9, 12, 24, 30 and 48 h following inoculation. PR1 and NPR1 were up-regulated and PR2 were down-regulated in‘Manicure Finger'. PR1, PR2, NPR1 were upregulated in Ciputao.【Conclusion】Disease resistance in Chinese wild Vitis variedamong species and genotypes. Variation in resistance, even within the same species, was not related to geo-graphic distribution. Therefore, Chinese wild Vitis present an essential germplasm resource for breedingnew varieties resistant to white rot. Disease resistance mechanisms were very different in Chinese wildgrapes. Further investigation is needed for clarifying the mechanism of resistance to white rot in grapes.