Effects Of Endophyte Infection On Drought Resistance To Drunken Horse Grass (Achnatherum Inebrians)

Drunken horse grass (Achnatherum inebrians) is one of intoxicating grasses growing at native grassland in Northwestern China, which has obvious advantages on growth in arid and semi-arid alpine grasslands under adverse environmental conditions. The endophyte of Neotyphodium gansuense which is symbiotic with A. inebrians, its biological and physiological characteristics, disease and insect resistance of the grass caused by endophyte has been studied. However, the effect of the endophyte on drought resistance is scarce.In this paper, seed germination, seedlings and mature growth, and drought-related physiological criteria on A. inebrians was studied under osmotic and drought stress conditions. Effects of endophye on drought tolerance to drunken horse grass in different growth stage were determined. Interactions and relationships of N. gansuense, A. inebrians and water scheme were theoretically clarified. The main results are as follows:1. The endophyte infection rates of A. inebrians in Xiahe, Yuzhong were as high as over 90%. Leaf sheaths, stem piths, seeds of A. inebrians were infected by endophytic mycelia.2. Under conditions of osmotic stress in germinator, endophyte could increase the germination rate, accelerate germination speed and promote growth of radicle and embryo of A. inebrians seeds collected from arid area. Under strong osmotic stress, endophyte infected (E+) plants of drunk house grass from the arid region, its germination rate, germination index, and length of radicle and embryo were significantly higher than those of endophyte free (E-) plants (p<0.05). However, seed germination rate, germination index and length of radicle and embryo between E+ and E- plants originated seeds in humid area were not significantly different (p>0.05).3. Under conditions of osmotic stress in greenhouse, endophyte could significantly increase leaf relative water content (LRWC), number of leaves and leaf elongation of seedlings of A. inebrians originated from arid area. Number of leaves and the leaf elongation of E+ seedlings from arid area were significantly higher than those of E-seedlings (p<0.05). However, the differences of leaf number and leaf elongation between E+ and E- seedlings from humid areas were not significantly different (p>0.05).4. Under conditions of nature drought stress in outdoor, the effects of endophyte on tiller number, leaf growth and LRWC of A. inebrians were not significantly different (p>0.05). The oxidative damage of E+ plants from arid area was significantly belower than that of E-plants (p<0.05), but the photosynthetic performance between E+ plant and E-plants was not significantly different (p>0.05). The superoxide dismutase (SOD) activity of E+ leaves from arid area was significantly lower than that of E- leaves (p<0.05), but there was no significant difference (p>0.05) between E+ and E- leaves from humid area.5. Whether under the conditions of osmotic or drought stresses in greenhouse or outdoor, compared with the E- plants from arid region, endophyte could obviously promote leaf proline accumulation and underground biomass accumulation of E+ plants (p <0.05), increase or maintain underground biomass, change biomass pattern by redistributing, i.e.: root/shoot ratio was increased. However, there were no significant differences from humid area (p>0.05).6. In drought recovery trials, endophyte could increase tiller and leaf growth of A. inebrians from arid area under the strong stress conditions, and slow down the degradation of proline, which enhanced A. inebrians recovery after drought stress. However, their drought recovery capabilities were not affected by endophyte of grass from humid area.