三江源区高寒草地不同生境土壤可培养纤维素分解真菌群落结构特征研究

为了解三江源区不同生境土壤可培养纤维素分解真菌的群落结构特征,在黄河流域、长江流域、澜沧江流域共选取有代表性的12个样点,采集土层0~15cm,15~30cm的土壤样品,采用稀释平板法在羧甲基纤维素钠平板培养基上进行可培养真菌的计数和分离,利用种群优势度、Shannon-Wiener多样性指数、均匀度、生态位宽度以及群落相似度等指标对不同生境土壤中可培养纤维素分解真菌群落结构特征进行了分析。结果表明,三江源区不同生境土壤可培养纤维素分解真菌的数量和类群差异明显,数量由大到小的顺序为:灌丛草地嵩草草地藏嵩草草地禾草草地;在4种生境土壤中共分离获得土壤可培养纤维素分解真菌17属,禾草草地土壤中群落的优势度指数、物种多样性指数、均匀度指数最高,除均匀度指数外,藏嵩草草地土壤中群落的优势度指数、物种多样性指数最低;物种生态位结果分析表明,毛霉属、镰孢菌属、被孢霉属、青霉属具有较宽的生态位,属于广适性物种;而亚隔孢壳属、梭孢壳属、腐质霉属等的生态位很窄,属于狭适性物种,只存在于某个生境中。禾草草地与藏嵩草草地土壤可培养纤维素分解真菌群落的相似性最低,灌丛草地和嵩草草地相似性最高。土壤纤维素分解真菌的群落结构及多样性与生境类型的特异性有着密切的关系。     

玉米秸秆对风沙土土壤微生物的影响

本研究以新型沙袋沙障为研究对象,分别对不同内部添加物、不同外层材料袋沙障内部、外部风沙土土壤细菌、真菌、放线菌及土壤微生物总量进行了测定。结果表明:沙袋沙障内添加玉米秸秆、玉米芯营养物质能够有效改善沙袋沙障内部风沙土环境,沙障内部微生物数量显著提高,微生物总数量分别达到了7.35×10~7 cfu/g、9.47×10~7 cfu/g,分别是对照(只灌装风沙土)沙袋沙障的113.11倍、145.62倍,并且添加玉米芯的作用效果更加显著,土壤微生物总数比添加玉米秸秆的高28.77%;添加玉米秸秆、玉米芯均对土壤真菌的影响较大,真菌数量可升高至微生物总数量的50%以上;玉米秸秆、玉米芯添加量越多,微生物数量越多,添加物体积百分比达到20%时,土壤微生物总数达到了1.01×10~8 cfu/g,随着添加量的继续增加,沙障内微生物数量无显著增加趋势;3种外层材料黄麻纤维、玻璃纤维、稻草沙袋沙障内部微生物总数排序为黄麻纤维>稻草>玻璃纤维,黄麻纤维沙障内部土壤细菌、真菌、放线菌三者总数分别比稻草、玻璃纤维的高58.80%、112.64%。     

Characterization,phylogenetic analyses and pathogenicity of Bipolaris setariae associated with brown stripe disease on sugarcane in Yunnan,China

Brown stripe disease is a severe foliar fungal disease of sugarcane worldwide and is widespread in all sugarcane planting areas in China. Brown stripe is a major disease that seriously affects the output and quality of the sugarcane industry in Yunnan Province, China's second-largest sugar base, while the pathogen of this disease remains not yet fully understood. To address this, we isolated and identified the fungi associated with 68 leaf samples showing typical symptoms of brown stripe from 22 sugarcane varieties in different areas of Yunnan Province. A total of 113 isolates were obtained, which were morphologically similar. Of these, 64 representative isolates were sequenced for the internal transcribed spacer region (ITS), GAPDH and EF-1α loci. All representative isolates grouped with the type strain of Bipolaris setariae in the phylogenetic trees inferred with individual and concatenated sequences of ITS, GAPDH and EF1-α. Pathogenicity test results showed that B. setariae strains were able to induce typical symptoms of brown stripe. The results obtained in this study clarify that only B. setariae is associated with sugarcane brown stripe in Yunnan, China. It is recorded here for the first time as a pathogen causing sugarcane brown stripe in Yunnan, and it is able to infect many major cultivars and new varieties, posing a new threat to the sugar industry in Yunnan Province. In addition, these results provide the scientific basis for the future breeding of disease-resistant varieties and effective prevention and control of sugarcane brown stripe disease.     

无纺布白僵菌条防治萧氏松茎象试验

2010-2011年在信丰林区开展了无纺布白僵菌条防治萧氏松茎象成虫试验。结果表明,2010．2011年试验区萧氏松茎象当年肴虫株率平均分别下降71．2％和76．7％;相对防治效果平均分别为75．0％和78．9％。这说明无纺布白僵菌条能明显抑制萧氏松茎象种群的上升。     

球囊霉属真菌与芽孢杆菌M3-4协同作用降低马铃薯青枯病的发生及其机制初探

 丛枝菌根真菌(AMF)和根围促生细菌(PGPR)能在一定程度上拮抗土传病原物、提高植物抗病性而降低病害。本研究旨在(1)确定不同AMF与PGPR组合中,菌间相互作用的关系;(2)评价不同AMF与PGPR组合促进马铃薯生长、降低青枯病(Ralstonia solanacearum)危害的效果;(3)初步探索最佳AMF与PGPR组合降低马铃薯青枯病的作用机制。结果表明,与单接种AMF或PGPR相比,一些AMF与PGPR组合能够促进AMF的侵染和PGPR在马铃薯根围的定殖; AMF与PGPR组合能显著促进马铃薯的生长(如株高、茎粗、地上鲜重、地上干重、薯块重),其中以AMF摩西球囊霉(Glomus mosseae, Gm)与PGPR芽孢杆菌(Bacillus sp.)M3-4菌株组合以及地表球囊霉(G. versiforme, Gv)与 M3-4菌株组合促生效果最好。另外,接种AMF和PGPR的组合不同程度降低了马铃薯青枯病的危害,其中也以Gm与M3-4和Gv与M3-4的组合防治效果最佳,防治效果分别为65.2%和69.5%。并且,后者处理的叶片中超氧化物歧化酶、苯丙氨酸解氨酶和过氧化氢酶活性显著高于其他处理,丙二醛含量则显著低于其他处理。实验结果表明,Gm与M3-4以及Gv与M3-4的AMF和PGPR组合能够协同作用大幅促进马铃薯的生长、诱导其防御反应而降低马铃薯青枯病危害。     

腐殖酸对花生连作地土壤真菌群落结构的影响

土传病害的绿色防控是当前农业、生态和环境领域中为建立资源节约型、环境友好型病虫害可持续治理技术体系的重要组成部分。将来自藓类泥炭和风化煤的腐殖酸添加至两个花生种植年限的土壤中（1年和6年）,进行室内恒温培养。对土壤真菌进行内部转录间隔区（internal transcribed spacer,ITS）测序,运用非参数多因素方差分析（PerMANOVA）、相关性分析等方法阐释腐殖酸对土壤真菌群落的影响。结果表明：腐殖酸的添加显著影响了培养94 d以后的土壤真菌群落结构,而添加量对4个培养时间点的土壤真菌群落结构均可产生显著影响;同时腐殖酸显著改变了部分真菌属的相对丰度。腐殖酸对土壤真菌功能的影响,主要表现为显著改变了土壤中真菌功能营养型的组成。其中,随着腐殖酸添加量的增加,土壤植物病原菌的相对丰度均显著降低;相关性分析表明腐殖酸添加量与致病菌镰刀属（Fusarium spp.） 和丝核菌属（Rhizoctonia spp.）的相对丰度呈显著负相关,而与拮抗菌青霉属（Penicillium spp.）的相对丰度呈显著正相关。本研究表明,特定腐殖酸在适当添加量下可显著改变花生地的土壤真菌群落结构和功能营养型组成,尤其是降低了土壤中植物病原菌的相对丰度,但影响程度因花生种植年限的长短而异。本研究结果为腐殖酸生态功能应用拓展提供了理论依据,为土传病害绿色防控技术的研发提供新的视角。     

离体条件下水稻种衣剂对串珠镰刀菌生长及形态毒理影响

 检测了黑龙江水稻主产区4个当地主栽品种的种子内部镰刀菌寄藏情况,测定了20%克福甲和20%克多甲种衣剂对种子带菌消毒处理效果及对水稻串珠镰刀菌(Fusarium moniliforme)的抑菌作用和联合毒力,并借助扫描电镜观察了上述2种混配种衣剂对串珠镰刀菌的形态毒理影响。结果表明,种子内部镰刀菌的分离频率高达56.7%~96.0%,其中串珠镰刀菌的分离频率为32.6%~48.2%,2种种衣剂对带菌种子具有显著的消毒处理效果。20%克福甲和20%克多甲种衣剂对镰刀菌F.moniliforme的毒力指数分别为457.11和802.04,增效倍数分别为6.53和0.13。20%克多甲种衣剂(多菌灵:甲基立枯磷为5:5,W/W)对串珠镰刀菌的抑菌作用优于20%克福甲种衣剂(福美双:甲基立枯磷为8:6,W/W),增效作用低于20%克福甲种衣剂。电镜观察表明,种衣剂低浓度至高浓度处理下均可引起串珠镰刀菌菌丝不同程度的异常生长,表现为主菌丝局部膨大或形成菌丝束,菌丝顶端异常膨大、缢缩或形成穗状和花絮状分枝。     

Comparative antifungal activities and biochemical effects of monoterpenes on plant pathogenic fungi

The antifungal activity of twelve monoterpenes, camphene, (R)-camphor, (R)-carvone, 1,8-cineole, cuminaldehyde, (S)-fenchone, geraniol, (S)-limonene, (R)-linalool, (1R,2S,5R)-menthol, myrcene and thymol was evaluated against four plant pathogenic fungi Rhizoctonia solani, Fusarium oxysporum, Penecillium digitatum and Asperigallus niger by using mycelial growth inhibitory technique. (S)-limonene and thymol were examined for their inhibitory effects on pectin methyl esterase (PME), cellulase and polyphenol oxidase (PPO) of tested fungi. Thymol was the most potent antifungal compound against the four test fungi with EC₅₀ values of 33.50, 50.35, 20.14 and 23.80 mg/L on R. solani, F. oxysporum, P. digitatum and A. niger, respectively. The antifungal activity of thymol was comparable to a reference fungicide, carbendazim. (S)-limonene and 1,8-cineole exhibited pronounced antifungal activity against the four tested fungi. The most effective antifungal compounds thymol and (S)-limonene showed strong inhibitory effect on the activity of PME and cellulase but revealed no inhibitory effect on PPO. The results showed that PME was more sensitive than cellulase to thymol and (S)-limonene. This is the first report on the inhibitory effects of monoterpenes thymol and (S)-limonene on PME, cellulase and PPO. The results indicated that monoterpenes may cause their antifungal activity by inhibiting PME and cellulase. The strong antifungal activity of thymol, (S)-limonene and 1,8-cineole reported in this study indicated that these compounds have a potential to be used as fungicides.     

Evaluation of the combination of 1,3-dichloropropene and dazomet as an efficient alternative to methyl bromide for cucumber production in China

BACKGROUND: The combination of 1,3‐dichloropropene (1,3‐D) and dazomet (DZ) offers a potential alternative to methyl bromide (MB) for soil disinfection. MB is scheduled to be withdrawn from routine use by 2015 in developing countries. Combination treatments of 1,3‐D + DZ were evaluated in a laboratory study and in two commercial cucumber fields. RESULTS: Laboratory studies found that nearly all of the tested combinations of 1,3‐D and DZ displayed positive synergistic activity on root‐knot nematodes (Meloidogyne spp.), two major soilborne fungi (Fusarium spp. and Phytophthora spp.) and the seeds of two major weed species (Digitaria sanguinalis and Abutilon theophrasti). Field trials revealed that the combination of 1,3‐D and DZ (at 10 + 25 g m^?2) successfully suppressed Meloidogyne spp. root galling, sharply reduced Fusarium spp. and Phytophthora spp. and maintained high cucumber yields. The combination treatment of 1,3‐D + DZ was more effective than 1,3‐D or DZ alone and provided results similar to methyl bromide with respect to pest control, plant mortality, plant height, yield and income. All of the treatments were significantly better than the non‐treated control. CONCLUSION: The results indicate that the tested combination of 1,3‐D and DZ offers an efficient alternative to methyl bromide for cucumber production. Copyright © 2012 Society of Chemical Industry     

The complex symbiotic relationships of bark beetles with microorganisms: a potential practical approach for biological control in forestry

Bark beetles, especially Dendroctonus species, are considered to be serious pests of the coniferous forests in North America. Bark beetle forest pests undergo population eruptions, causing region wide economic losses. In order to save forests, finding new and innovative environmentally friendly approaches in wood-boring insect pest management is more important than ever. Several biological control methods have been attempted over time to limit the damage and spreading of bark beetle epidemics. The use of entomopathogenic microorganisms against bark beetle populations is an attractive alternative tool for many biological control programmes in forestry. However, the effectiveness of these biological control agents is strongly affected by environmental factors, as well as by the susceptibility of the insect host. Bark beetle susceptibility to entomopathogens varies greatly between species. According to recent literature, bark beetles are engaged in symbiotic relationships with fungi and bacteria. These types of relationship are very complex and apparently involved in bark beetle defensive mechanisms against pathogens. The latest scientific discoveries in multipartite symbiosis have unravelled unexpected opportunities in bark beetle pest management, which are discussed in this article.