Effects Of Endophyte Infection On Pest Resistance To Drunken Horse Grass

Drunken horse grass (Achnatherum inebrians), an intoxicating and water and soil conservation grass growing at native grassland in northwest of China, symbiotic with endophyte of Neotyphodium gansuense was studied in this paper. It maily included survey of pest density, feeding trials and ergot alkaloids detection. The results summarized as followings:1. Seed germination experiment showed that compared with endophy-free (E-) seeds, germination rate, germination index, shoot length and root length of endophyte-infected (E+) seeds were increased.2. Pest investigation showed that there were significantly higher densities of bird-cherry-oat-aphid (Rhopalosiphum padi) and carmine spider mite (Tetranychus cinnabarinus) on E- plants than those on E+ plants (p<0.05), under greenhouse pot condition, outdoor pot experiment and field conditions, respectively.3. Physilogical effects by aphid piercing-sucking showed that leaf relative water content (LRWC) and chlorophyll content (CC) were decreased significantly (P<0.05) with feeding by bird-cherry-oat-aphids. The aphid number of E+ plants was significantly lower than those on E- plants (P<0.05). Compared with trial beginning, enzyme activities of SOD, POD were increased significantly (P<0.05). Only under 20 aphids/plant for 4 days, there was significant (P<0.05) fewer number of E+ plants that those on E- plants. The contents of MDA and proline were increased significantly (P<0.05) by aphid piercing-sucking.4. Feeding trial of detached leaves showed that, compared with E+ leaves, the aphids performed the preference on E- leaves, there was significant lower number of aphids on E+ plants than those on E- plants (p<0.01). After 2-3 weeks of inoculation of aphids onto growing plants, mortality on E+ plants was significantly higer than that on E- plants (p<0.05). However, progenitive number on E+ plants was significantly lower than that on E- plants (p<0.05). 5 Mowing trial showed that mowing height could affect the contents of ergine and ergonovine, there were significantly different (p<0.05) between once per week and once per two weeks mowing, and among the three height grades of 2.5 cm, 5.0 cm, 7.5 cm. There was significantly different (p<0.05) between weekly and biweekly mowing of both alkaloids.6 Correlations analyses showed that there was significantly negative correlation between content of ergonovine (r=-0.901, p<0.01) and ergine (r=-0.981, p<0.01), respectively, and populatioin number of bird-cherry-oat-aphid. There was also significantly negative correlation between content of ergonovine (r=-0.977, p<0.01) and ergine (r=-0.982, p<0.01), respectively, and population number of carmine spider mite.