Physiological,Guality,Agronomic Traits Differences And Analysis Of Candidate Genes For Resistance To Disease Of Foxtail Millet Varieties Resistant And Susceptible To Downy Mildew

Foxtail millet is one of the main coarse cereals in north of China.In recent years,with the increase in the planting area of foxtail millet,the Sclerospora graminicola has become one of the devastating diseases in foxtail millet production,seriously affecting the yield and quality.In order to clarify the differences in physiology,quality,agronomic traits and gene expression of foxtail millet after inoculation with S.graminicola so as to provide a certain theoretical basis for resistant breeding,the study compared the physiological,quality,and agronomic traits of the resistant and susceptible varieties selected in the laboratory.At the same time,the field resistance to S.graminicola was identified through the hybrid progeny of the resistant and susceptible foxtail millet varieties,and then the RT-PCR analysis and the analysis of the CAP gene family related to disease resistance clarified the differences in gene expression of resistant and susceptible varieties.The main findings are as follows:1.The 50 foxtail millet varieties that showed different degrees of resistance to the incidence of S.graminicola,obtained by the research group in the early stage,were analyzed for differences in physiology,quality,and agronomic traits:(1)By measuring the physiological differences in stomata area,stomata density,wax content,lignin content,photosynthesis,chlorophyll content,etc.of resistant and susceptible foxtail millet varieties,it was found that there were significant differences in the stomata of resistant and susceptible varieties.,While the stomata of disease-resistant varieties are relatively long and narrow.There was no significant difference between the stomata density of the epidermis of the resistant varieties and the susceptible varieties;the determination of the wax content showed that the wax content of the resistant varieties was significantly higher than that of the susceptible varieties;the chlorophyll content of the resistant varieties was obvious after inoculation of S.graminicola.It is higher than that of susceptible varieties;the lignin content of susceptible varieties is significantly lower than that of resistant varieties.(2)Through the determination of total carotenoids,folic acid content,beige color,protein and amino acid content of resistant and susceptible varieties,the total carotenoids of resistant varieties are less than those of susceptible varieties,but the difference is not significant;the content of folic acid in resistant and susceptible varieties It is not significant,and there is a significant difference in amino acid content;the beige of susceptible varieties is better than that of resistant varieties;the protein content of resistant varieties is higher than that of susceptible varieties.(3)Through the investigation of the agronomic traits of the screened resistant varieties,it was fo und that there were significant differences in the agronomic traits of the resistant varieties.Among them,the plant height,ear length,ear weight and thousand-grain weight of resistant varieties were significantly higher than those of susceptible varieties,while there were no significant differences in ear thickness and stem thickness.2.Through the field indirect fungi,phenotypes and incidence statistics of 209 hybrid progeny populations constructed by the parents JG21 and GBS,it was found that the hindband population showed significant resistance differences.Among them,38 varieties were identified as immune,23,24,68,47 and8 varieties were identified as highly resistant,resistant,medium resistant,susceptible and highly susceptible,respectively.Earlier analysis of transcriptome data of resistant cultivar GBS and susceptible cultivar JG21 revealed that 9 genes,Seita.2G024600,Seita.9G290900,Seita.9G298200,Seita.6G228600,Seita.6G225400,Seita.5G278500,Seita.8G141000,Seita.6G246300,Seita.5G277900 were differentially expressed in resistant foxtail millet cultivars.RNA was extracted and analyzed by RT-PCR.All genes were up-regulated at 24 h except Seit A.8G141000 and Seit A.9G298200,while the expression of all genes was down-regulated at 48 h and 72 h.Seita.8G141000 and Seita.9G298200 genes were up-regulated in resistant cultivars and down-regulated in susceptible cultivars,consistent with the transcriptome sequencing results,suggesting that these two genes may be involved in the anti-susceptible response of foxtail millet.Through the above studies,it was found that resistant cultivars differed in physiology,quality and agronomic traits.At the same time,B115,B156,B22 and other resistant and high quality cultivars and two candidate genes of resistance to S.graminicola were obtained,namely Seita.8G141000 and Seita.9G298200,which are expected to provide research basis for screening excellent resistance germplasm resources and cloning of resistance genes.