通过测定一系列生理变化指标，研究人工接种条件下禾谷缢管蚜(Rhopalosi p hum padi (L.))对带内生真菌(E+) 与不带菌(E-) 醉马草(A chnatherum inebrians (Hance) Keng) 幼苗的影响。结果表明:在一定时期内，禾谷缢管蚜刺吸可使醉马草幼苗叶片相对含水量和叶绿素含量显著降低(P<0.05)，同一个虫口密度E + 与E-植株之间差异显著(P<0.05)；幼苗体内SOD 活性和POD 活性均随危害时间的延长而显著升高(P<0.05)，同一个虫口密度E+与E-植株之间差异显著(P<0.05)；接种蚜虫可使MDA 和游离脯氨酸的含量显著提高(P<0.05)，同一个虫口密度内E+与E-植株之间差异显著(P<0.05)。综上所述，内生真菌的侵染可以在一定程度上间接影响禾谷缢管蚜取食，进而影响醉马草幼苗生理生化的变化。

Root-invading fungi of milk vetch (Astragalus adsurgens) at different growth stages grown in three ages of sown pasture soil were studiedin Huanxian county, Gansu province, China. Pathogenicity was tested by seed and soil inoculation. A total of 44 fungi were isolated from milkvetch roots, 32 from the roots of field plants and 37 from the roots of potted seedlings. The total percentage of root segments yielding fungalcolonies increased with age of plants; they were 70.5%, 82.3% and 97.8% in 1-, 3-, and 5-year-old plant roots, respectively, differences thatwere significant (P<0.05). The frequency of isolation from roots of plants at re-greening, branching, flowering and yellowing growth stageswere 62.0%, 95.3%, 93.0% and 83.7%, respectively. The total percentage of root segments yielding fungal colonies from 3-, 6-and 12-weekoldpotted seedlings were 21.8%, 44.7% and 32.0%, respectively, differences that were also significant (P<0.05). Seedlings were easilyinfected and symptoms of damping-off disease were common in seedlings younger than 3-week-old. Of the 44 fungi isolated and tested forpathogenicity by seed inoculation, 19 decreased seed germination rate, 12 decreased seedling shoot length, and 22 decreased seedling rootlength. Fusarium solani, F. oxysporum, F. chlamydosporum, F. avenaceum and Gliocladium roseum were strongly pathogenic to milk vetch. Insoil inoculation tests, these same fungi (except for F. chlamydosporum) decreased seedling root dry matter production significantly(P<0.05), but seed germination and seedling survival were not affected by any of these fungi.

Microsatellites are often highly variable and abundant in most complex genomes, therefore are widely used in population genetic studies. In this study, twelve polymorphic microsatellite loci were isolated and characterized for the Achnatherum inebrians, a plant abundant in grasslands of Northwest China. Characterization of 24 A. inebrians individuals form four geographically distant populations (Gansu, Qinghai, Xinjiang and Inner Mongolia provinces) showed moderate to high allelic diversity ranging from 3 to 13 alleles per locus, and the expected heterozygosity ranging from 0.41 to 0.67. No evidence of linkage disequilibrium was found for any locus pairwise comparisons. The markers described here will be useful for investigating the genetic diversity, genetic structure and gene flow of this species.

The effect of the endophyte Neotyphodium lolii on susceptibility of perennial ryegrass (Lolium perenne) to ten fungal pathogens in detached leaves was studied. The pathogens were Alternaria alternata, Ascochyta leptospora, Bipolaris sorokiniana, Curvularia lunata, Fusarium acuminatum, F. avenaceum, F. chlamydosporum, F. solani, F. oxysporum, and Gliocladium roseum. In addition, the effect of the endophyte on four pathogens (A. alternata, B. sorokiniana, Curvularia lunata and F. avenaceum) in living plants was studied, and changes in host superoxide dismutase (SOD) or peroxidases (POD) activity were examined. The total lengths of lesions on detached leaves were greater (P<0.05) on Eplants than on E+ plants except for A. leptospora although differences between E+ and E- were not consistently significant at all sample times (days after inoculation).The numbers of lesions were greater (P< 0.05) and the lesions were larger (P<0.05) on intact E- plants than on intact E+ plants for all of the four pathogens. SOD enzyme activity was significantly greater (P<0.05) in E+ plants than in E- plants only for A. alternata, C. lunata, and F. avenaceum. POD enzyme activity was significantly greater (P<0.05) in E+ plants than in E- plants only for C. lunata, B. sorokiniana and the uninoculated control.

Achnatherum sibiricum is a threaten and toxic perennial bunchgrass mainly in the north of China. We developed 11 polymorphic microsatellite loci from A. sibiricum by combining biotin capture method. After validating and scoring, these loci were polymorphic in a test population with the range of alleles from four to 13 per locus. The observed and expected heterozygosities ranged from 0.1649 to 0.5624 and from 0.3071 to 0.8826, respectively. All 11 microsatellite markers were in Hardy– Weinberg equilibrium. These polymorphic microsatellites will be useful for genetic diversity analysis and population structure construction for A. sibiricum.