丛枝菌根与植物寄生性线虫相互作用及抗性机制

丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)能够与大多数陆地植物互惠共生,促进植物对养分的吸收,提高植物对各种生物和非生物胁迫的抗逆性,对植物健康生长有重要的作用。在土壤中丛枝菌根真菌与植物寄生性线虫共同依靠寄主植物根系完成生命循环,但二者对寄主植物作用完全相反,引起研究者广泛兴趣,成为菌根研究的热点和焦点之一。本文分析了丛植菌根真菌与植物寄生线虫的相互作用,并探讨了菌根提高植物对线虫抗性的可能机制:菌根真菌改善植物的生长和营养状况、改变植物根系形态结构、影响根系分泌物和根际微生物区系、诱导寄主植物产生防御反应等,旨在深入挖掘丛枝菌根真菌的生物学功能,进一步发挥其在农业生产中的应用潜力。     

温室土壤食物网静态和动态结构特征

Soil food web structure is fundamental to ecosystem process and function; most studies on soil food web structure have focused on agro-ecosystems under different management practices and natural terrestrial ecosystems, but seldom on greenhouses. This study explored the static and temporal variability of soil food structure in two greenhouses of Shandong Province, North China over a two-year period. The static properties were measured directly by surveying functional group composition and a series of parameters portraying the species properties, link properties, chain properties and omnivory properties of the web, as well as indirectly through calculation of nematode indices, enrichment index （EI）, structure index （SI）, and channel index （CI）. The dynamic variability of greenhouse soil food structure was described by the dynamics of functional groups, Bray-Curtis （BC） similarity and cluster analysis. The results showed that the greenhouse soil food web contained 14 functional groups, with microbes having the highest mean biomass, followed by protozoa. Of the three functional groups of protozoa, flagellates were the dominant group on most sampling dates, amoebae only became the dominant group during the summer, while ciliates were the least prevalent group. All nematodes were assigned into one of the four functional groups, bacterivorous, fungivorous, herbivorous and omnivorous, and the fungivorous nematodes had the lowest mean biomass. Mites were assigned into three functional groups and the omnivorous noncryptostigmatic mites were the dominant group. All the functional groups showed significant seasonal changes. The soil food web connectance was 0.15, the maximum food chain length was 5, and the average food chain length was 3.6. The profiles of the EI and SI showed that the food web was resource- depleted with minimal structure. The results of CI indicated that the bacterial decomposition pathway was the dominant pathway in the food web of the greenhouse soils studied and the results of BC similarity showed that the soil food web had higher variability and instability over time. The cluster analysis showed that the functional groups located at high trophic levels with low biomass were in a cluster, whereas those at low trophic levels with high biomass were closer. Compared with the food web structure of agroecosystem and natural terrestrial ecosystem soils, the structure of greenhouse soil food web was simple and unstable, which was likely driven by high agricultural intensification, particularly over application of fertilizers.     

Global status of nematode problems of groundnut, pigeonpea, chickpea, sorghum and pearl millet, and suggestions for future work

Analysis of responses received from 40 cooperators in 20 countries to a questionnaire on nematode problems of groundnut, pigeonpea, chickpea, sorghum and pearl millet suggested that Meloidogyne spp. are internationally important nematode pests of groundnut, chickpea and pigeonpea. Pratylenchus spp. are important on all the five crops. In India, Heterodera cajani and Rotylenchulus reniformis are important pathogens of pigeonpea. Over the last 10–15 years, extensive nematode disease surveys have been undertaken for these crops in Australia, Egypt, India, Jamaica, Senegal, Sudan, Thailand and Zimbabwe; however, < 10% of the total crop areas were covered by these surveys. Except for Brazil, Egypt, USA and Zimbabwe, growers do not use nematicides to control the nematodes. Cultural practices, especially crop rotations, are the most commonly used control measures. Species of Meloidogyne, Pratylenchus and Rotylenchulus on the legumes, and species of Hoplolaimus, Pratylenchus, Quinisulcius and Xiphinema on the cereals, are strongly suspected of increasing the severity of fungal diseases. Work aimed at finding host resistance is being done in Brazil, Fiji, India and the USA, and some sources of resistance have been identified against Meloidogyne arenaria, M. incognita, M. javanica and R. reniformis. Facilities for resistance screening work now exist in many countries. Information on damage thresholds of important pest species are available only from Brazil, Fiji, India and the USA.     

Pine wilt disease: a short review of worldwide research

This article summarizes the results of the research papers presented at the International Symposium on pine wilt disease (IUFRO Working Party Meeting 4.04.03) held in July 2009, at Nanjing, China. The general topics covered were on pine wilt disease (PWD), its causal organism, the pinewood nematode (PWN) Bursaphelenchus xylophilus, plus other PWN-associated microorganisms that play a significant role in PWD such as bacteria (e.g. Pseudomonas fluorescens). Most of the papers that are reviewed are based on work on PWD-PWN in East Asia and Russia. Specific topics covered include: 1) the fundamental conceptions of PWD development, 2) pathogenicity, 3) host-parasite relationships including the histopathology of diseased conifers and the role of toxins from bacteria-nematode ecto-symbionts, 4) PWN life cycle and transmission, 5) B. xylophilus dissemination models, 6) associations (with other nematodes), 7) diagnostics, 8) quarantine and control of the PWN and 9) biocontrol of the PWN.     

The relative resistance to gastrointestinal nematode infection of three British sheep breeds

The relative resistance of Manx Loaghtan, Shetland and Southdown sheep to naturally acquired gastrointestinal nematode infection was assessed over a ten week period. Thirty shearling ewes, ten from each of the three breeds, were co-grazed on an infective pasture. The animals were initially treated with an anthelmintic to minimise previous nematode infection, and faecal samples were collected from individual animals every two weeks. Southdown sheep had significantly higher faecal egg counts (FEC) than Shetland by week 6, and than Manx Loaghtan by week 10. After ten weeks there was an 86-fold difference in FEC between Shetland and Southdown sheep, and a 14-fold difference between Manx Loaghtan and Southdown sheep. These preliminary results suggest that primitive Shetland and Manx Loaghtan sheep may have greater resistance to gastrointestinal parasites, a trait that could be of value to the UK livestock industry.     

Effectiveness of strategic anthelmintic treatments in the control of gastrointestinal nematodes and <Emphasis Type="Italic">Fasciola gigantica</Emphasis> in cattle in Iringa region,Tanzania

A longitudinal field trial was conducted to determine the effectiveness of strategic anthelmintic treatments in the control of gastrointestinal (GI) nematodes and Fasciola gigantica in cattle. A total of 167 cattle (6–18 months) from three large-scale dairy farms, four traditional farms and nine small-scale dairy farms were randomly selected. The selected animals on each farm were ear tagged and allocated into three groups based on live weight and treated as follows: Group T4 was treated with albendazole 10% drench at 10 mg/kg four times a year (mid rainy, end of the rain, mid dry and late dry/early rainy season). Group T2 was treated with albendazole 10% drench at 10 mg/kg two times a year (mid rainy and late dry/early rainy season). Group UT remained as untreated control. Faecal, blood and pasture samples were taken every month for 13 months. In addition, individual body weight (BWT) was measured on every sampling date. Results showed that two and four strategic treatments significantly reduced faecal egg counts (FEC) by 49.5% and 62.3% respectively compared to untreated control animals (P < 0.001). Two and four strategic treatments per year significantly reduced the proportion of animals passing Fasciola eggs in faeces by 30.6% and 51.7% (P < 0.001), respectively. Animals treated two and four times a year significantly outgained untreated animals by 14.8 kg and 17.7 kg respectively at the end of the trial (P < 0.05). The management system had a significant effect on packed cell volume and the proportion of animals passing Fasciola eggs in faeces (P < 0.05). The programme of two strategic treatments per year was only effective in controlling GI nematodes. It is concluded that a programme of four strategic treatments per year was effective in controlling GI nematodes and F. gigantica and improved weight gain.     

青海省门源县石头沟地区牛羊胃肠线虫病的调查

石头沟地区放牧的牛羊每年一到秋末或冬季便出现消瘦、贫血、浮肿、被毛脆弱,容易脱落。为此笔者进行调查,走访14户农户,采集了58头牛羊粪便。结果表明,牛羊的胃肠线虫种类很多,往往混合感染,对牛羊危害极大。结果检查出牛羊的线虫感染率为39.01%。     

沈阳地区番茄根寄生线虫种类鉴定

１９９０～１９９１年对沈阳地区露地番茄根寄生线虫进行了详细的分类鉴定，共鉴定出７个属１３个种线虫：垫刃线虫属Ｔｙｌｅｎｃｈｕｓ１个种：Ｔｙｌｅｎｃｈｕｓｍａｉｕｓ；丝尾垫刃线虫属Ｆｉｌｅｎｃｈｕｓ３个种；Ｆｉｌｅｎｃｈｕｓｂｕｔｔｅｕｓ，Ｆ．ｓａｎｄｎｅｒｉ；螺旋线虫属Ｈｅｌｉｃｏｔｙｌｅｎｃｈｕｓ１个种：Ｈｅｌｉｃｏｌｙｌｅｎｃｈｕｓｅｘａｌｌｕｓ；矮化线虫属Ｔｙｌｅｎｃｈｏｒｈｙｎｃｈｕｓ２个种：Ｔｙｌｅｎｃｈｏｒｈｙｎｃｈｕｓｂｒｅｖｉｃａｕｄａｔｕｓ，Ｔ．ｉｒｒｅｇｕｌａｒｉｓ；短体线虫属Ｐｒａｔｙｌｅｎｃｈｕｓ１个种：Ｐｒａｌｙｌｅｎｃｈｕｓｈｅｘｉｎｃｉｓｕｓ；滑刃线虫属Ａｐｈｅｌｅｎｃｈｏｉｄｅｓ４个种：Ａｐｈｅｌｅｎｃｈｏｉｄｅｓｃｉｂｏｌｅｎｓｉｓ，Ａ．ｐａｒａｂｉｃａｕｄａｔｕｓ，Ａ．ｓｕｂｐａｒｉｅｔｉｎｕｓ；真滑刃线虫属Ａｐｈｅｌｅｎｃｈｕｓ１个种：Ａｐｈｅｌｅｎｃｈｕｓａｖｅｎｏｅ，其中６个种在国内未见报道。     

滑刃线虫属（Aphelenchoides Fischer,1894）的2个国内新记录种

描述了滑刃线虫属（Aphelenchoides Fischer,1894)的2个国内新记录种：游泳滑刃线虫(Aphelenchoides hechaleos)和内卷滑刃线虫(A.involutus)。游泳滑刃线虫采自辽宁省盖州市熊岳镇莴苣(Lactuca sativa)的根际土壤中，它与近似种拟游泳滑刃线虫(A.paranechaleos)的主要区别是雌虫尾较长，尾的形状是腹面凸（而拟游泳滑刃线虫的尾较短，尾的形状是背面凸，腹面凹），雄虫交合刺背杆的弯曲程度较小。内卷滑刃线虫采自辽宁省凌海市苍耳(Xanthium sibiricum)及山东济南大花金鸡菊(Coreopsis grandiflora)的根际土壤中，它与近似种A.jacobi的主要区别是雌虫尾向腹面弯曲程度较大，尾后部呈钩状，尾较长。