Tao Y. Plant-breeding Value of Wheat is Depending on the Functional Features of Powdery Mildew Phytopathogens

The dissertation work provides a theoretical foundation and practical solution to the issues of creating source material of winter wheat with resistance to powdery mildew for breeding purposes and establishing the molecular and genetic basis of plant resistance to powdery mildew. The urgent task of modern science is to expand theoretical research and solve practical problems in order to create varieties with a controlled level of powdery mildew. Therefore, the authors identified the adult disease resistance of powdery mildew in 86 new wheat lines. The experiment was conducted at the Wheat Test Base in Henan Province in 2020–2022. The test materials were from 45 relevant breeding units in China. There are 86 new wheat lines. The test carried out powdery mildew resistance identification. And analyzing the source of disease resistance genes. In the 2020 resistance test for powdery mildew, only 11.7% of the 86 new wheat lines identified performed well. There is no line of disease resistance in the adult stage that is immune or near-immunized. There are four lines that are highly resistant to disease during the adult stage. There are two lines with moderate resistance to disease in the adult stage. There are four lines that are moderately susceptible. They accounted for 4.7%, 2.3%, and 4.7% of the total identified materials, respectively, and the overall resistance was poor. We use pedigree analysis and parental resistance to disease to derive disease resistance genes for varieties that are resistant to disease. It is speculated that the genetic sources of some powdery mildew-resistant varieties may be Aikang 58, Jimai 22, Yumai 34, Zhengmai 366, Liangxing 66, Zhoumai 16, Zhoumai 18, Yumai 47 and Xiaoyan 926A. In the early stages of this research, the yeast two hybrid (Y2H) cDNA library was constructed using the excellent common wheat variety Bainong 64, which has been widely promoted in production and has completed genome sequencing. Based on Y2H, Pm46 was used as a bait protein to screen the Y2H system cDNA library, and the function of the obtained interacting protein genes, which may be related to the resistance of disease, was preliminary proved. As a result, TaGDSL, a gene that plays a positive regulatory role in wheat powdery mildew resistance, was cloned and characterized. Cloning of the Pm46 gene: the Pm46 gene was cloned from the cDNA of Bainong 64, with a total length of 1545 bp and encoding 514 amino acids. Screening the interaction protein of Pm46 by Y2H: In-Fusion technology was used to introduce the CDS of Pm46 into the yeast double hybrid bait vector pGBKT7 to construct the pGBKT7-Pm46 bait vector. The growth of yeast has no toxic effect or self-activation effect, indicating that the full length of Pm46 can be used as a bait to screen the Y2H system libraries; in this study, 5 proteins interacting with Pm46 that may be related to disease regulation were screened by Y2H. Function verification of the interacted protein genes: the gene silencing system induced by barley stripe mosaic virus (BSMV-VIGS) was used to silence 5 of the screened interacted protein genes, which may be related to the resistance to disease in the common wheat of Bainong 207, respectively. The results show that TaGDSL plays an active regulatory role in the powdery mildew resistance pathway. The over-expression vector of the TaGDSL gene and the RNAi interference vector were constructed, and the vectors were transferred into the common wheat Bainong 207 by the Agrobacterium infection method. The stable knockdown expression of TaGDSL plants was built by Agrobacterium tumefaciens transformation. The results also showed that wheat was more susceptible to disease when the TaGDSL gene was silenced, and the result is consistent with the VIGS assays. The germination and mycelia growth rates of powdery mildew on the leaves of positive transgenic plants were much faster than those of wild-type wheat leaves. The silencing (RNAi) TaGDSL plants had enhanced powdery mildew resistance. Functional identification of the TaGDSL gene from wheat by the long-growth period assay proved that silencing of the TaGDSL gene could resist powdery mildew in wheat plants. After inoculation with powdery mildew, the straw biomass, grain, number of spikelets, and 1000-grain weight of the RNAi lines were significantly higher than those of the WT lines at maturation. These results support the idea that TaGDSL is an active regulator of powdery mildew resistance. Our findings demonstrate that TaGDSL silencing is potentially useful since it can help generate genetically modified genotype materials with powdery mildew resistance in wheat.