Several species of Achnatherum (grass tribe Stipeae) and Melica (tribe Meliceae) typically are infected by nonpathogenic, seed-transmissible fungi with characteristics of Neotyphodium species (anamorphic Clavicipitaceae). Molecular phylogenetic studies clearly have distinguished the endophytes from Achnatherum inebrians (from Xinjiang Province, China), A. robustum and A. eminens (both from North America) and indicate that the A. inebrians endophyte comprises a unique nonhybrid lineage within the Epichloe and Neotyphodium phylogeny, whereas the endophytes of A. robustum, and A. eminens are hybrids with multiple Epichloe species (holomorphic Clavicipitaceae) as ancestors. Likewise distinct hybrid origins are indicated for Neotyphodium species from the European Melica species, M. ciliata and M. transsilvanica, the South African species M. decumbens and M. racemosa, and the South American species M. stuckertii. Neotyphodium species have been described from A. inebrians from Gansu Province, China, (N. gansuense), A. eminens (N. chisosum), M. stuckertii (N. tembladerae) and the South African Melica species (N. melicicola). However the endophytes from A. robustum and the European Melica species have not been described and the phylogenetic relationships of N. gansuense have not been investigated. Here we report a comprehensive study of morphological features and phylogenetic analyses of b -tubulin and actin gene sequences on an expanded collection of endophytes from the Stipeae and Meliceae. These data provide a firm foundation for the description of two new Neotyphodium species, N. guerinii from M. ciliata and M. transsilvanica, and N. funkii from A. robustum. We also propose the new variety, N. gansuense var. inebrians for endophytes of A. inebrians from Xinjiang Province, which are morphologically and phylogenetically distinct from, yet clearly related to, N. gansuense from Gansu Province.

综述了国内外近年来关于内生真菌Neot y p hodi um 对禾草类植物抗旱性方面的研究成果。结果表明:与不带菌禾草相比,带菌禾草的抗逆性强、产量高,特别是内生真菌的侵染可增加宿主植物的抗旱性。据报道,内生真菌主要是通过促进植株根系发育、叶片生长、气孔开闭、渗透调节、抗氧化保护系统等来提高禾草类植物的抗干旱胁迫能力。但也有学者认为并非所有内生真菌对宿主禾草的抗旱性都有增益作用,内生真菌与禾草的共生关系还很大程度上决定于宿主、内生真菌基因型和生境的相互关系。在未来的研究中应以内生真菌- 禾草共生体的抗旱机理、生物学特性和群体特征为重点;此外利用真菌-禾草共生体的抗旱特性开展优良牧草草坪草选育,发挥内生真菌在天然草地中的生态作用也是重要的研究方向。

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.

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.

通过饲喂试验,研究了带内生真菌(E+)和不带内生真菌(E-)的醉马草对家兔健康的影响。内生真菌的侵染,使醉马草粗脂肪含量显著提高,粗蛋白和粗纤维含量无显著改变。按10 mL /kg体重的剂量灌服E+醉马草水提液,家兔表现出明显的中毒症状;但累计灌服20mL/kg体重的剂量,亦未引致死亡。平均按每kg体重累计饲喂E+醉马草131.6g,可引起家兔中毒;累计饲喂350.9g可使家兔致死,死亡率达66.7%。而灌服和饲喂E-醉马草的家兔则无异常。初步认为,醉马草对家兔的致毒机理是由内生真菌与宿主互作产生的生物碱所致。