Technology Of Evaluation Of Aegilops Species For Resistance To Rhopalosiphum Padi And Mechanism Of Aphid-induced Resistance

Rhopalosiphum padi linne (Homoptera: Aphidiae) is one of important pests which danger wheat. This thesis explored new methods of resistance evaluation and mechanism of resistance through studying on resistance of 5 Aegilops species induced by the feeding of Rhopalosiphum padi linne. The results showed:1. 5 accessions, Aegilops biuncialis, Aegilops kotschyi var. variabilis, Aegilops juvenalis, Aegilops ovata and Aegilops ventricosa, which have different resistance levels, from Aegilops species were evaluated for resistance to Rhopalosiphum padi by the aphid number ratio, necrosis area and the chlorophyll ratio of area unit. The comparisons of evaluation were expected. The necrosis area induced by the feeding of Rhopalosiphum padi was positively related to the aphid number ratio significantly (R=0981^**). The chlorophyll ratio of area unit of 5 Aegilops species which had different resistance levels was negatively related to the aphid number ratio significantly(R=-0.970^**).2. Analyse the resistance of 5 Aegilops species induced by the feeding of Rhopalosiphum padi: after 10-day feeding, the enzyme activities of Polyphenol Oxidase(PPO), Peroxidase(POD), Catalase(CAT), Phenylalanine Ammonia-lyase (PAL) were raised with certain degree in the plant respectively compared to those before feeding, the increasing ratio of enzyme activities which were raised with the resistance levels of species had relations to the aphid number ratio(R=-0.824, -0.856, -0.710, -0.754 and -0.884^*, respectively), and were negatively related to necrosis area significantly(R=-0.920^*,-0.922^*,-0.907^*及-0.953^*). The stepwise regression equation for the increasing ratio PPO, POD and PAL enzyme activities and necrosis area is Y_area=0.187-0.0356 X_POD [F=17.0065, F_0.05(1, 3)=10.1, F_0.01(1, 3)=34.1], which showed the increasing ratio of PPO and PAL enzyme activities were not negatively related to necrosis area significantly without the synergism of the increasing ratio of POD enzyme activity. All these facts possibly indicated that they were somethings to do with the induce of aphid's feeding which would raise with the resistance level of species. PPO and POD synergetically resist to aphid in Aegilops species. The synergy of the increasing ratio of PPO activity by POD is much more than PPO do to the increasing ratio of POD.3. Analyse the threshold of insect number which was enough to induce the resistance of Aegilops by their feeding: A. biuncialis which was with high resistance was much more sensitive to the feeding of Rhopalosiphum padi, that's to say, two aphids' or less feeding could induce the resistance. By comparison, only the feeding of 11 aphids or more could induce the resistance of A. ventricosa which was with high susceptibility and was insensitive to the feeding probation of Rhopalosiphum padi.4. Analyse the threshold of feeding time which was enough to induce the resistance of Aegilops: A. biuncialis which was with high resistance was much more sensitive to the feeding of Rhopalosiphum padi and was induced to resist the aphid's feeding in much earlier time, that's to say, 2 hours feeding or less could induce the resistance of plant which was sensitive to the feeding probation of aphid. By comparison, the resistance of A. ventricosa which was with high susceptibility and was insensitive to the feeding probation could be induced by the aphid's feeding after 8 hours.