Abstract:

In order to preliminarily reveal the resistance mechanism of sunflower to Verticillium Wilt at the physiological and molecular levels,the resistant sunflower variety SC89 and susceptible variety LD5009 were used as materials,and the content of H₂O₂,the activities of defense enzymes superoxide dismutase(SOD),catalase(CAT),peroxidase(POD)and phenylalanine ammonia lyase(PAL)were measured and the transcription level of key genes in disease resistance signaling pathways were analyzed after the sunflower varieties inoculated with the toxin of Verticillium dahliae.The result showed that H₂O₂ increased rapidly in the resistant variety SC89 at 6 h after inoculation and reached the highest value at 12 h and 36 h,respectively,0.55,0.60 μmol/g,then decline,while in the susceptible variety,although there was a small peak,0.17 μmol/g,at 12 h after inoculation,the accumulation level was far lower than the resistant variety.In the resistant variety,the activity of SOD,CAT,POD and PAL reached the peak rapidly in a short period of time,and then gradually decreased.While the susceptible variety,the peak value of these ROS scavenging enzymes were lower than that of resistant varieties.At the same time,after inoculation,the six disease resistance related genes such as Pr5,Pal and ROS scavenging enzyme gene Sod,Sco and Cat had in varying degrees of induced expression.These results indicated that signal molecules such as SA,JA and H₂O₂ played important roles in the process of sunflower resistance to Verticillium Wilt.

Key words: Sunflower, Verticillium Wilt, ROS, Signaling molecules