The Preliminary Study On Mechanisms Of Resistance To Aphids In Brassica Napus L. Conferred By Piriformospora Indica

Piriformospora indica is a root endophytic fungus, which was isolated from Thar Desert in India, forms an association with roots of many plant species. The fungus has captable to stimulate growth, increase biomass and enhance production of the hosts. It also confers the host resistance against abiotic and biotic stresses.Aphid is the most serious pest on rape, mainly for the Myzus persicae, Lipaphis erysimi and Brevicoryne brassicae L.. Because of the strong fecundity, high feed intake and spreading various viruses, aphids cause serious impact on rape yield.In this thesis, Piriformospora indica-rape symbiont was established to confirm the resistance to aphids in Brassica napus L. conferred by Piriformospora indica and preliminarily study the mechanisms. The salient findings of the research are:1. P. indica inoculated B. napus significantly repelled aphidsRapes colonized by P. indica significantly interfered the positioning of aphids to rapes. Aphid dual-choice assay in the greenhouse and laboratory artificial environment indicated that P. indica inoculated B. napus (Bn+Pi) significantly repelled aphids. And aphid dual-choice assay of rape leaf discs also indicated that Bn+Pi significantly repelled aphids. Meanwhile some aphids turned to P. indica-free B. napus(Bn-Pi) after eating Bn+Pi.2. Volatiles emitted by Bn+Pi were significantly different to that emitted by Bn-PiVolatiles analysis showed the total amount of volatiles emitted by100g Bn+Pi plant per hour was significantly higher than Bn-Pi plant. The volatile compounds, whose amount had significantly different between Bn+Pi and Bn-Pi plants, belonging to monoterpenes and sesquiterpenes, were a-pinene, terpinolene, camphor, β-thujene, a-cedrene and β-caryophyllene.3. L. erysimi had different reactions to volatile compoundsThe result of four-sector olfactometer assay indicated that single component α-pinene attracted L. erysimi, camphor repelled L. erysimi, and other components had no effects to aphids. Blend1, blend2and blend3also had significant repellent to aphids. The quantity of the components in the volatiles was also responsible for the differential attraction and repellency of L. erysimi. When the concentration was low (10-6g mL-1), blend1had the strongest repellency to L. erysimi, while camphor most repelled L. erysimi under high concentration (1g mL-1).4. Bn+Pi significantly reduced the food assimilation of aphidThe food assimilated by L. erysimi on Bn+Pi decreased32.7%compared to Bn-Pi. And it may be relevant to the significantly increasing of γ-aminobutyric acid in Bn+Pi plant.