The Study On The Resistant Identification Of Sunflower Varieties And Resistance Mechanism To Sunflower White Mold

Sunflower Sclerotinia, caused by Sclerotinia sclerotiorum (Lib) de Bary(S. sclerotiorum), is a serious sunflower disease around the world. The lacking of natural resistance sources limited the resistant breeding progress to S. sclerotiorum. In this research, we studied the characteristics of S. sclerotiorum, classified the resistant level of sunflower varieties to S. sclerotiorum under the field condition and unravel the resistant mechanism of high resistant varieties. These results will be layed a theoretical foundation for sunflower resistance breeding in the future. Our results listed in follows:1. The inoculation plug position in the cultural plate has the influences on the pathogenicity of S. sclerotiorum. The further the distance of the inoculation plug to the centre of cultural plate, the much stronger pathogenicity was observed. Meanwhile, the distance of the inoculation plug to the centre of the plate also have the same effects on the oxalic acid (OA) production and PG enzyme activities. The more further to the center, the more OA secreted and more PG enzymes activity was detected.2. The passage number has the effects on the pathogenicity of S. sclerotiorum When the passage number is over20times, the obvious reduced effects among the different passage times was aboserved.3. Winter broad irrigation was found not only inhibit the germination rate and mycelial growth speed, but also decrease the oxalic acid secretion and the PG enzyme activity. The pathogenicity was also observed decreased both on the detached leaves and also on the living plant. Thus, winter irrigation can be used as one of agricultural practices to control the Sunflowe White Mold.4. The resistance identification of different sunflower varieties to sunflower white mold was tested under field condition in three different locations (Guyuan of Ningxia, Wuyuan and Chifeng of Inner Mongolia). Our results suggested that there not only have significant differences on the resistance leve among all the testes varieties in the same field, but also the same variety showed different resistant level at different tested fields. In addition, the same sunflower varity showed different resistant level in different tested sites, suggesting the virulence variation of S. sclerotiorum do exist in the sunflower planting fields in China.5. Inoculation of S. sclerotiorum under field and laboratory conditions on detached leaves and stem of living plants facilitated us to select oil seed varieties Faguo land Xinkuiza5as the material to unravel the resistant mechanism of sunflower to S. sclerotiorum.6. Using Faguo land Xinkuiza5, we unraveled the resistance mechanism of Faguo1through detecting the callose deposition, necrotic cells number, soluble protein content, activity of SOD, POD, PAL, CAT enzymes and H2O2level. The results indicated that more callose deposition on the cell wall、low number of necrotic cells、high amount of soluble protein content、high level of H2O2accumulation fast and high ROS scavenge enzymes activities were observed in resistant variety Faguol.7. The transcript level of resistant related genes was detected also in this study. Our results suggested that SA synthesis genes Pal and downstream effector gene Def, JA pathway marker gene Pr5and H2O2pathway related genes Sco, Cat and Sod were upregulated by S. sclerotiorum, indicating the involvement of SA, JA,and H2O2signaling molecules in the resistance mechanim establishment in Faguol.