Identification of resistance to anthracnose in leaves of grape resources and QTL localization of disease resistance genes

Abstract：【Objective】Grape anthracnose is one of the main diseases of grape, which mainly infects the fruits, young leaves and new branches of grape, causing fruit rot, shedding, or water loss and shrinkage into stiff fruits. Breeding disease-resistant grape varieties is the most economical, effective, and environmentally friendly long-term control strategy for the prevention of the anthracnose disease. There have been a few studies on the identification of the resistance to anthracnose and the QTL localization of relative disease resistant genes so far. The study aimed to identify the resistance to the anthracnose disease of different grape germplasms and seek for new QTL locus for the resistance and provide germplasm materials and basis for the breeding and research on the disease resistance mechanism.【Methods】The indoor ex vivo leaf inoculation method was used to identify and evaluate the resistance to anthracnose in 60 strains of Chinese wild grapes, 122 accessions of V. vinifera and 76 accessions of V. vinifera-V. labrusca, and the hybrid offsprings of Manicure Finger (susceptible)×Ciputao0940 (resistant), and the QTL localization of grape anthracnose resistance was carried out using the genetic map constructed by SNP markers.【Results】A total of 1 germplasm with high resistance, 43 germplasms with resistance and 75 germplasms with medium resistance were screened out, accounting for 0.39% , 16.67% and 29.07% of the total identified accessions, respectively. There were great differences in the resistance to anthracnose in different germplasm populations. 63.34% of the East Asian population 56.57% of the V. vinifera-V. labrusca population, and 31.15% of the Eurasian population had the resis-tance to anthracnose. In the identification of anthracnose resistance in Chinese wild grape germplasms, it was found that the resistance of different strains in the same population varied greatly, and the species with strong resistance on the whole included V. davidii, V. pseudoreticulata, V. amurensis, and V. piasezkii. The strong resistance of the strains include Shanputao♀, Longyuwanfuye1♀, Duolieye-yingyu , Shanputao- shanyang1807, Mianmaoputao- chayu1955, and Ciputao0940. The resistance of the hybrid offsprings of Manicure Finger (susceptible)×Ciputao0940 (resistant) were distributed in five grades. According to the normality test and single-sample Kolmogorov-Smirnov test based on the resistance level distribution of the F1 population, it was found that the hybrid offsprings of Finger (susceptible) × Ciputao0940 (resistant) showed continuous variation in anthracnose resistance, which was a typical quantitative trait controlled by polygens, and the phenotypic distribution of disease resistance identification results showed a trend of partial normal distribution, which could be analyzed by QTL localization. In the positioning of QTL related to grape resistance to anthracnose, the interval or site of LOD≥3.0 was used as the threshold value for QTL, and when the above conditions were met, the site corresponding to the highest LOD value in the interval was considered to be one QTL of grape anti-anthracnose. In this experiment, a QTL interval associated with grape anthracnose resistance was detected on the 8th linkage group, and the locus with the highest LOD value in this interval was located at 140.682 cM, and the tightly linked label was Maker1675910, which could explain the 14.7% of the phenotypic variation. Based on the gene annotation results of the QTL locus interval, 15 resistance- related genes were screened out, and they were hypothesized to play a role in grape anthracnose resistance.【Conclusion】 The resistance level of different grape germplasms to anthracnose was clarified, one QTL site against anthracnose was located and 15 resistant-related genes were screened.