Suppressive effects of seed-applied fungicides on arbuscular mycorrhizal fungi (AMF) differ with fungicide mode of action and AMF species

Seed-applied fungicides are commonly used to prevent or suppress fungal disease organisms in pulse crop production. However, non-target beneficial fungi, such as arbuscular mycorrhizal fungi (AMF), also may be affected. Seed-applied fungicides Agrox^® FL (active ingredient: captan), Allegiance™ FL (metalaxyl), Apron Maxx^® RTA^® (fludioxonil and metalaxyl), Thiram 75WP (thiram), Vitaflo^® 280 (carbathiin and thiram), Crown^® (carbathiin and thiabendazole), and Trilex^® AL (trifloxystrobin and metalaxyl) were assessed in a greenhouse study for their effects on colonization and development of AMF in pea and chickpea, and the consequent impact on plant growth. In the absence of disease pressure, systemic fungicides Allegiance™ FL, Apron Maxx^® RTA^®, Vitaflo^® 280, Crown^® and Trilex^® AL restricted mycorrhizal colonization, host growth and P uptake to different levels. In contrast, contact fungicides Agrox^® FL and Thiram 75WP had minimal effects on mycorrhizal colonization, host growth and P uptake. Although consequent sporulation and glomalin-related protein production were not significantly affected by fungicides at an early host growth stage, the compositional structure of the AMF community in host roots was significantly altered in response to Agrox^® FL, Allegiance™ FL, Apron Maxx^® RTA^®, and Trilex^® AL as revealed by pyrosequencing-based analysis of fungal 18S rRNA. These results indicate that the suppressive effects of seed-applied fungicides on AMF development depend on specific fungicide-AMF interactions.     

Problems of using pines in <Emphasis Type="Italic">Tuber melanosporum</Emphasis> culture: soils and truffle harvest associated with <Emphasis Type="Italic">Pinus nigra</Emphasis> and <Emphasis Type="Italic">P. sylvestris</Emphasis>

In Mediterranean pine forests, truffles and mushrooms generate greater profits than any other woodland products. However, there are no studies on Tuber melanosporum Vittad. associated with pines. For this reason, we have carried out a study of this truffle in mountain woods with Pinus sylvestris L. and P. nigra Arnold subsp. salzmannii (Dunal) Franco, in central Spain. Two hundred and eight Tuber melanosporum burns were monitored for 7 years in five different habitats within the same geographical area. An ANOVA test confirmed significant differences in carpophore production. In higher producing habitats, pines were less abundant. We also confirmed that in 433 burns, T. melanosporum was always unequivocally associated with the root base of Quercus or Corylus trees. Similarly, 14 truffle collectors confirmed that they had never found a single burn with carpophore production associated exclusively with pines. Nevertheless, soil analyses indicated that the soil of these pine woods was very favourable to Tuber melanosporum. We therefore conclude that at present Pinus nigra salzmannii and P. sylvestris are of little interest to Tuber melanosporum culture, as they hinder carpophore production. However, this study has also confirmed that Pinus nigra salzmannii and P. sylvestris mycorrhize easily with Tuber melanosporum, both in the laboratory and in natural environments. On this basis, we propose that pines may act as transmitters of T. melanosporum, although they do not induce fruiting. As a result, the commercial cultivation of Pinus nigra salzmannii and P. sylvestris seedlings mycorrhized with Tuber melanosporum is not recommended in truffle culture at the present time.     

Dual inoculation of a woody legume (Centrolobium tomentosum) with rhizobia and mycorrhizal fungi in south-eastern Brazil

The integration of N₂ fixing trees into stable agroforestry systems in the tropics is being tested due to their ability to produce high biomass N and P yields, when symbiotically associated with rhizobia and mycorrhizal fungi. The growth of Centrolobium tomentosum Guill. ex Benth, a native leguminous tree from the Brazilian Atlantic Forest, was assessed with dual inoculation of Rhizobium spp and mycorrhizal fungi under field conditions. Complete fertilization was compared to treatments of inoculation with selected rhizobia strains BHICB-Ab1 or BHICB-Ab3, associated or not to arbuscular mycorrhizal (AM) fungi. The dual inoculation increased the height and growth in relation to the plants treated with rhizobia alone. Plants inoculated with strain BHICB-Ab1 and arbuscular mycorrhizal fungi (AMF) exhibited an increase of 56% dry matter over uninoculated control and nitrogen accumulation was greater than with BHICB-Ab3 inoculated plants. Strain BHICB-Ab1 presented a synergetic relationship with mycorrhizal fungi since the combined inoculation with BHICB-Ab1 enhanced plant height and dry weight more than single inoculation while the growth of BHICB-Ab3 plants was not modified by AMF inoculation. Arbuscular mycorrhizal fungi enhanced plants survival and seemed to favour the nodule occupation by rhizobia strains as compared to the non-mycorrhizal plants. Inoculation with selected rhizobia and AMF improved the growth of C. tomentosum under field conditions. This revised version was published online in June 2006 with corrections to the Cover Date.     

松褐天牛成虫高毒力菌株的筛选试验

松褐天牛不仅本身对树木的生理和工艺造成损害,而且是松材线虫在松林间传播的媒介昆虫,对松木造成巨大危害。该文选用了7株虫生真菌对松褐天牛成虫进行了生物测定,结果表明不同菌株的毒力存在差别,其中以金龟子绿僵菌Ma83菌株的毒力最强,天牛的校正死亡率及感染率都最高,分别10 0 %和79% ,致死中时也最短,LT5 0为5 .2 4d ,致死中浓度LC5 0为1.3 8×10 - 6 孢子 ml.松墨天牛成虫虫体不同部位与无纺布菌条的接触感染实验表明,触角、口器、足和腹的感染率依次升高,致死中时依次下降。     

真菌降解木质素的研究现状

在介绍木质素结构的基础上 ,从降解木质素的菌种及主要酶、产酶的条件 ,分析了真菌降解木质素的研究现状 ,介绍了真菌降解木质素及其酶的应用 ,并提出了存在的问题及发展方向     

紫金山两种主要林型有机物层中丝状真菌多样性

本文对紫金山两种主要林型,栓皮栎林(Quercus variabilis)和马尾松-枫香(Pinus massoniana-Liguidam barformasana)混交林的有机物层(L, F, H层及土壤淋溶A层)可培养丝状真菌多样性进行了研究。通过分离鉴定,共得到真菌67种,其中接合菌3种、子囊菌5种、半知菌类56种和未确定种3种,半知菌类最为丰富。两种林型分解真菌优势种群为链格孢(Alternaria sp.)、曲霉(Aspergillus spp.)、枝孢(Cladosporium sp.)、毛霉(Mucor sp.)、青霉(Penicillium sp.)、木霉(Trichoderma spp.)、根霉(Rhizopus sp.)、粘帚霉(Gliocladium sp.)。混交林型中真菌的种类和数量明显高于栓皮栎林。两个林型均以F层真菌种类最多,但F层之间和L层之间真菌多样性差异较大。在混交林型中从马尾松针叶上分离的真菌种类和数量比从枫香上分离得到的少; 从马尾松针叶上分离的真菌丰富度随着有机物层深度增加而增加,枫香则反之。比较两个林型以及混交林的两种落叶上真菌种类发现,随着有机物层深度的增加,真菌的种类差异性却随之减少,即同时出现在两个林型或两种针叶上的真菌种类增多。真菌种类随着分解过程的进行具有明显的演替现象。混交林型中同一层内不同落叶上分解真菌多样性的差异,表明凋落物基质的差异是决定真菌种类和数量的重要因素     

三种桉树菌根菌培养条件的研究

多根硬皮马勃9215、彩色豆马勃9216及西澳粘滑菇E4070菌株是广东地区应用较多、效果也较好的菌根真菌,为摸清其培养条件,分别进行了适温范围、最适pH以及C源、N源需求的测定。其结果表明:菌株9216适温范围最广,为10～38C,菌株E4070适温范围最窄,为15～30C;最适pH范围以9215菌株最广,为3～7,菌株E4070最窄,仅为5～7;除菌株9216不能利用有机N源中的牛肉膏及酵母浸膏外,其它8种N源均有不同程度的利用,9215菌株对有机N利用较好,而9216菌株对氨态N利用较好;除9215菌株对果糖的利用较差外,其它C源差异不大,菌株9216对麦芽糖及葡萄糖利用较好,而E4070对6种C源利用效果差异不大。     

树木菌根真菌——美味红菇复合制剂的生物效应*

在探明菌根真菌美味红菇生理活性物质的基础上,为使其实用化,又从该菌的发酵液中提取并研制成真菌复合制剂。除在医学上进行了一系列抗菌活性试验外,同时还在育苗造林上,利用不同树种进行防病保苗促进生长的生物活性试验。本文主要报道应用美味红菇复合制剂对几种亚热带针阔叶树种幼苗和种子进行体内生物活性的试验结果。目的在于观察和研究该复合制剂对促进幼苗生长和提高抗生能力的生物效应,以便进一步开拓美味红菇复合制剂的有效应用范围和途径。     

竹材霉变生物学的研究*Ⅰ.毛竹材致霉菌与致霉特征

确证15种霉菌可引起毛竹材霉变，对这15种霉菌的分类学形态特征及其在毛竹材上诱致的霉变外貌特征进行了详细描述；指出其中10种霉菌为毛竹材重要致霉菌，提出在竹材霉变试验中可选用菌体相对覆盖量目测法估计竹材霉变程度。