禾草-内生真菌共生体在草地农业系统中的作用

综述了国内外近年对禾草 -内生真菌 (N eotyphodium)的研究进展。全世界现已报道 14种禾草内生真菌 ,与 2 3个属的禾草形成共生体 ,我国已在 13属 2 5种天然草地禾草中发现内生真菌 ,其中发草属 (Descampsia)、大麦属 (H ord eum)和赖草属(L eymus)以往在国际文献中未曾报道。内生真菌在禾草体内产生的生物碱 ,致使采食带菌禾草的马、牛、羊、鹿等家畜产生中毒症状 ,每年给美国、新西兰等国造成的经济损失达 6.4亿美元之多 ,对其毒理研究取得了进展。已发现我国醉马草 (Achnatheruminebrians)对家畜的毒性与内生真菌的侵染有关。内生真菌侵染增加可使禾草对 42种害虫的抗性 ,并可增加对某些线虫和病害的抗性。与不带菌禾草相比 ,带菌禾草的另一特点是抗逆性强 ,牧草产量高。国际在该领域的研究主要集中在多年生黑麦草(L olium p erenne)和高羊茅 (Festuca arundinacea)。我国的研究发现 ,带菌布顿大麦草 (H ordeum bodg anii)和圆柱披碱草(Elymus cylind ricus)的牧草产量分别增加 3 3 .3 %和 2 78.8% ,分孽数分别增加 13 6.8%和 84.5%。目前 ,国际研究的重点包括大规模开展内生真菌生物学与生态学特性的研究 ,创造不含对家畜有害毒素的有益禾草 -内生真菌共生体 ,培育带内生真菌的草坪草品种 ,培育抗毒

Roles of the grass-Neotyphodium association in pastoral agriculture systems

Neotyphodium (syn. =Acremonium) endophytes are a group of fungi which live for all, or at least a significant part of their life cycle asymptomatically within grass plant parts. Innumerable studies on graminicolous endophytic fungi have been carried out internationally in the fields of mycology, pasture agronomy, animal and plant sciences and veterinary science during the last 25 years. Research on endophytes started in the early 1990's in China. In this paper research progress on the grass-endophyte association both in China and overseas was reviewed and key areas for further study were suggested. Fourteen Neotyphodium species have been formally identified and reported from 23 genera of grasses in the world literature. Endophytes have been found in 13 genera and 25 species of forage grasses in native grasslands in China. Among these host plants, Descampsia, Hordeum and Leymus genera have not been reported as Neotyphodium hosts previously in the world literature. Endophytes produce alkaloids within the host plant, which are toxic to livestock, including cattle, sheep, horses and deer grazed on Neotyphodium infected grasses. It has been estimated that the livestock industry in the United States and New Zealand suffers more than 640 million US dollars in lost production annually due to the endophytes. Fortunately the mechanism of toxicity has been understood and the chemicals responsible for livestock toxicosis identified. It was found that the toxicity of drunken horse grass in China was related to endophyte infection. The effects of endophyte infection on drunken horse grass toxicity to livestock are being studied in a series of feeding trials. One of the most beneficial effects conferred by endophytes on their host grasses is the production of toxins and feeding deterrents which reduce insect grazing. About 42 insect species have been reported worldwide to be deterred or adversely affected by feeding on endophyte infected grasses. Another beneficial effect imparted to grasses by endophytes is tolerance to environmental stresses. Compared with grass not infected, plants with endophytes showed better adaptation to drought and heat conditions, and produced higher herbage dry matter yield. Reported research of this type has mainly focused on ryegrass (Lolium perenne) and tall fescue (Festuca arundinacea). Glasshouse and field studies carried out in China showed that, compared to the plants not infected with endophyte, the herbage dry weight of endophyte-infected Hordeum bogdanii and Elymus cylindricus was increased by 33.3% and 278.8%, and number of tillers per plant by 36.8% and 84.5%, respectively. Key areas for further research internationally include large scale research into the endophyte-grass association, and biology and ecology of endophytes, creating novel endophyte-grass association which are not toxic to livestock deter the negative effects of insects, breeding new turfgrass cultivars by introducing endophytes into existing turfgrass cultivars, selecting and breeding toxin tolerant livestock, genetic engineering research, and research into the role of endophytes in native grassland development.