木材腐朽菌在森林生态系统中的功能

木材腐朽菌是森林生态系统的重要组成部分,在森林生态系统中起着极为重要的降解还原作用,主要包括担子菌门非褶菌目、子囊菌门盘菌纲和半知菌类的部分真菌,能全部或部分降解木材中的木质素、纤维素和半纤维素,其降解机制有3种：白色腐朽、褐色腐朽和软腐朽．木材腐朽菌与生态系统中其它生物关系密切,为很多昆虫、鸟类提供营养,有些昆虫也能使木腐菌得到传播．保护木材腐朽菌的生物多样性是保护森林生态系统、维护生态系统健康的重要因素．     

The effects of wood decay type on the growth of bryophyte gametophytes

Deadwood is an important habitat for bryophytes in boreal and subalpine forests. The type of decay in wood (white, brown, and soft rot) caused by fungal colonizers has been revealed to affect bryophyte communities. However, little is known about the effects of decay type on the growth of bryophytes. We tested the effect of wood decay type on gametophyte growth for two common bryophyte species, Scapania bolanderi Austin and Pleurozium schreberi (Brid.) Mitt., which dominate the logs in subalpine coniferous forest on Mt. Ontake, in central Honshu, Japan. We used pot culture experiments in an open-sky nursery field. After eight months of cultivation, the growth of S. bolanderi was larger on brown rot wood than white rot wood, but the growth of P. schreberi was not. Mixed cultures of the two species also showed greater growth on brown rot wood. However, growth of S. bolanderi was significantly smaller than P. schreberi in mixed culture. These results suggest that brown rot wood enhances growth of S. bolanderi, but growth may be reduced under competition from P. schreberi. The results are in agreement with the field observation that brown rot wood has a positive association with S. bolanderi coverage on deadwood.     

First record and preliminary evaluation of Mucor hiemalis as biocontrol agent on inflorescence brown rot incidence of date palm

In Egypt, inflorescence brown rot disease of date plam trees caused by Thielaviopsis paradoxa De Syenes causing high losses of pollen grains and fruits yield productivity. Infection occurs early on spathes even when it still hidden in the leaf bases. White mycelium of pathogenic fungi grows on inflorescence then turned to brown when fungus spores abundant. Isolation trails from diseased spathes showed brown rot, yielded three genus of fungal i.e. Aspergillus niger (25%), Mucor hiemalis (25%) and T. paradoxa (50%). Pathogenicity test by using fungal isolates and male inflorescence of data indicate that, all isolates of T. paradoxa were able to induce brown rot of inflorescence. Isolates of T. paradoxa were differed in pathogenic activity for producing inflorescence brown rot symptom. Also, A. niger isolate could cause slightly decay on inflorescence. Meanwhile, all isolates of M. hiemalis recorded as non pathogenic. In vitro, dual culture technique by using M. hiemalis showed antagonistic properties against T. paradoxa. Scanning electron microscopy (SEM) study revealed that, pollen grains of date palm are susceptible to infection by T. paradoxa, accompanied by complete lyses and ruptured. SEM examination of inflorescence treated by each of M. hiemalis or/and T. paradoxa showed that M. hiemalis was able to colonisation on inflorescence and reduced colonisation of T. paradoxa on inflorescence and pollen grains. Preliminary evaluation of M. hiemalis as a biocontrol agent showed that, spray of inflorescence with M. hiemalis suspension two days before or after infestation by T. paradoxa were reduced brown rot of inflorescence than the control. Spraying of spathes by M. hiemalis before infestation by pathogen was highly effective in reduction brown rot incidence compared with spraying after infestation. These results help to explain the role of M. hiemalis in the suppression and biological control of T. paradoxa.     

Lignocellulosic polysaccharides and lignin degradation by wood decay fungi: the relevance of nonenzymatic Fenton-based reactions

The brown rot fungus Wolfiporia cocos and the selective white rot fungus Perenniporia medulla-panis produce peptides and phenolate-derivative compounds as low molecular weight Fe³⁺-reductants. Phenolates were the major compounds with Fe³⁺-reducing activity in both fungi and displayed Fe³⁺-reducing activity at pH 2.0 and 4.5 in the absence and presence of oxalic acid. The chemical structures of these compounds were identified. Together with Fe³⁺ and H₂O₂ (mediated Fenton reaction) they produced oxygen radicals that oxidized lignocellulosic polysaccharides and lignin extensively in vitro under conditions similar to those found in vivo. These results indicate that, in addition to the extensively studied Gloeophyllum trabeum—a model brown rot fungus—other brown rot fungi as well as selective white rot fungi, possess the means to promote Fenton chemistry to degrade cellulose and hemicellulose, and to modify lignin. Moreover, new information is provided, particularly regarding how lignin is attacked, and either repolymerized or solubilized depending on the type of fungal attack, and suggests a new pathway for selective white rot degradation of wood. The importance of Fenton reactions mediated by phenolates operating separately or synergistically with carbohydrate-degrading enzymes in brown rot fungi, and lignin-modifying enzymes in white rot fungi is discussed. This research improves our understanding of natural processes in carbon cycling in the environment, which may enable the exploration of novel methods for bioconversion of lignocellulose in the production of biofuels or polymers, in addition to the development of new and better ways to protect wood from degradation by microorganisms.     

Incidence and identification of Cassava tuber rot caused by Phytophthora palmivora

The occurrence of Cassava tuber rot in regions of Kolli hills, Kollam, and Kottayam of South India, causes major economic loss up to 70% in Cassava production. The disease tuber is characterised by brown watery lesions with foul smell, making it unfit for further use. The sporangia of the pathogen were oval and ellipsoid with a short pedicle. Identification of the isolate from these regions was also confirmed by ribosomal internal transcribed spacer (ITS) of rDNA region. The pathogen was highly aggressive when pathogenicity was tested. Based on morphological, pathogenicity and ITS sequences, the pathogen was identified as Phytophthora palmivora. Development of integrated disease management practices is essential to combat the disease. This is the first report recording the spread of Cassava tuber rot disease in regions of Kolli hills of Tamil Nadu and Kollam and Kottayam, of Kerala.     

Comparing lignocellulose physiochemistry after decomposition by brown rot fungi with distinct evolutionary origins

Among wood‐degrading fungi, lineages holding taxa that selectively metabolize carbohydrates without significant lignin removal (brown rot) are polyphyletic, having evolved multiple times from lignin‐removing white rot fungi. Given the qualitative nature of the ‘brown rot’ classifier, we aimed to quantify and compare the temporal sequence of carbohydrate removal among brown rot clades. Lignocellulose deconstruction was compared among fungi using distinct plant substrates (angiosperm, conifer, grass). Specifically, aspen, pine and corn stalk were harvested over a 16‐week time series from microcosms containing Gloeophyllum trabeum, Fomitopsis pinicola, Ossicaulis lignatilis, Fistulina hepatica, Serpula lacrymans, Wolfiporia cocos or Dacryopinax sp. After quantifying plant mass loss, a thorough compositional analysis was complemented by a saccharification test to determine wood cell wall accessibility. Mass loss and accessibility varied depending on fungal decomposer and substrate, and trajectories of loss for hemicellulosic components and cellulose differed among plant tissue types. At any given stage of decomposition, however, lignocellulose accessibility and the fraction remaining of carbohydrates and lignin within a plant tissue type were generally the same, regardless of fungal isolate. This suggests that the sequence of plant component removal at this typical scale of characterization is shared among these brown rot lineages, despite their diverse genomes and secretomes.     

桃树根部内生真菌ZJ-4的分离鉴定及其对桃褐腐病的抑制效果

自桃树根部组织中分离能够防治桃褐腐病害的内生拮抗真菌,并从细胞学水平对其抑制机理进行了初步的探究。采用两点对峙法筛选抑制桃褐腐病菌Monilinia fructicola的内生拮抗真菌,通过菌落形态学特点观察及ITS基因测序分析,初步鉴定内生拮抗真菌的系统发育学地位;采用果实离体实验检测内生拮抗真菌的抗菌效果;使用电子显微镜观察被内生拮抗真菌抑制的桃褐腐病菌丝、孢子的形态以及细胞结构的变化。分离得到的内生真菌ZJ-4对桃褐腐病防效高且稳定,初步鉴定为篮状菌属Talaromyces;果实离体试验表明,内生真菌ZJ-4明显降低了桃褐腐病的发病率;通过电子显微镜观察到被内生真菌ZJ-4抑制的桃褐腐病菌丝及孢子表面粗糙凹陷,畸形现象严重,胞质溶胶收缩凝聚,细胞内部出现大量的空腔。本研究筛选的ZJ-4对桃褐腐病原菌的生长有明显的抑制作用,为开发应用该菌株提供参考。     

Resistance of parenchyma cells in wood to degradation by brown rot fungi

Wood degradation by two basidiomycetes, Fomitopsis pinicola and Laetiporus sulphureus was studied in one conifer and four broadleaved trees: Picea abies (Norway spruce), Acer pseudoplatanus (sycamore), Betula pendula (birch), Quercus robur (common oak) and Robinia pseudoacacia (robinia). Observations of birefringence under polarized light showed that in all hosts both brown rot fungi affected cells of the early wood before those of the late wood. Degradation of cellulose, as shown by the loss of birefringence, was apparent after 6 weeks in the cell wall of fibres and fibre tracheids, but even after 12 weeks, axial parenchyma showed no signs of degradation. The results indicate that both brown rot fungi cause higher weight losses in hosts (P. abies and B. pendula) with a small amount of parenchyma cells, whereas the lowest weight losses are associated with wood containing a high amount of parenchyma cells (Q. robur and R. pseudoacacia). Resistance of parenchyma cells to degradation by brown rot fungi appears to be related to the cell wall morphology of parenchyma cells and may also reflect a low co-evolutionary adaptation of brown rot fungi to the xylem of broadleaved trees.     

Assessment of saccharification efficacy in the cellulase system of the brown rot fungus Gloeophyllum trabeum

Brown rot fungi uniquely degrade wood by creating modifications thought to aid in the selective removal of polysaccharides by an incomplete cellulase suite. This naturally successful mechanism offers potential for current bioprocessing applications. To test the efficacy of brown rot cellulases, southern yellow pine wood blocks were first degraded by the brown rot fungus Gloeophyllum trabeum for 0, 2, 4, and 6 weeks. Characterization of the pine constituents revealed brown rot decay patterns, with selective polysaccharide removal as lignin compositions increased. G. trabeum liquid and solid state cellulase extracts, as well as a commercial Trichoderma reesei extract (Celluclast 1.5 L), were used to saccharify this pretreated material, using β-glucosidase amendment to remove limitation of cellobiose-to-glucose conversion. Conditions varied according to source and concentration of cellulase extract and to pH (3.0 vs. 4.8). Hydrolysis yields were maximized using solid state G. trabeum extracts at a pH of 4.8. However, the extent of glucose release was low and was not significantly altered when cellulase loading levels were increased threefold. Furthermore, Celluclast 1.5 L continually outperformed G. trabeum cellulase extracts, although extent of glucose release never exceeded 22.0%. Results suggest methodological advances for utilizing crude G. trabeum cellulases and imply that the suboptimal hydrolysis levels obtained with G. trabeum and Celluclast 1.5 L cellulases, even at high loading levels, may be due to brown rot modifications insufficiently distributed throughout the pretreated material.     

New Insights into the Ecological Interaction Between Grape Berry Microorganisms and Drosophila Flies During the Development of Sour Rot

In this work, we studied the ecological interactions between grape berry microorganisms and Drosophila sp. flies involved in sour rot disease during grape ripening. After veráison the total microbial counts of grape berries affected by sour rot increased from about 2 log CFU/g of berries to more than 7 log CFU/g. Berry damage provoked a clear shift in yeast diversity from basidiomycetes to ascomycetous fermentative species. The latter were mostly Pichia terricola, Hanseniaspora uvarum, Candida zemplinina, and Zygoascus hellenicus. However, these species were not able to produce the metabolites characteristic of sour rot (gluconic and acetic acids) in inoculated berries. On the contrary, the acetic acid bacteria Gluconacetobacter saccharivorans produced high levels of these acids, mainly when berries were incubated in the presence of the insect Drosophila sp. Sour rot was not observed when grape bunches were physically separated from insects, even when berries were artificially injured. The wounds made in berry skin healed in the absence of insects, thus preventing the development of sour rot. Therefore, in the vineyard, the induction of sour rot depends on the contamination of wounded berries by a microbial consortium--yeasts and acetic acid bacteria--transported by drosophilid insects which disseminate sour rot among damaged berries. In the absence of these insects, plant defense mechanisms are effective and lead to skin healing, preventing disease spread. Thus, we showed that Drosophila sp. act as a vector for microorganisms associated with grape sour rot disease.     

Phylogenetic analysis of Antrodia and related taxa based on partial mitochondrial SSU rDNA sequences

Sequences of mitochondrial SSU rDNA were obtained from six species of Antrodia and related fungal taxa to reveal their phylogenetic relationships. Phylogenetic analysis showed that the species of Antrodia did not cluster into a single clade. Brown rot fungi were separated into two main groups through which Antrodia was dispersed. Antrodia sinuosa, A. serialis, A. heteromorpha and A. malicola clustered with Perenniporia, Fomitopsis, Piptoporus, Daedalea and Melanoporia within one group of brown rot fungi, while A. carbonica and A. vaillantii clustered with Oligoporus, Gloeophyllum and Auriporia within the other group of brown rot fungi, indicating that Antrodia is a heterogeneous genus and that brown rot fungi have evolved convergently. This revised version was published online in June 2006 with corrections to the Cover Date.     

Comparison of methods to evaluate the potential of fungal growth on decay of spruce wood after short-time treatment

Several analytical methods were compared to evaluate characteristic wood decaying fungi for their potential to depolymerise lignin on spruce wood particles. Wood samples were treated with the white rot fungi Phlebia brevispora, Ceriporiopsis subvermispora, Merulius tremellosus, Pycnoporus sanguineus, Trametes pubescens and with the brown rot fungus Gloeophyllum trabeum. The UV absorbancies of crude ethanol extracts, total extractives content from sequential extraction, ligninolytic enzyme activities, lignin solubilisation and decrease of lignin content were compared. It was shown, that, in early decay stages, UV absorbancies of crude ethanol extracts and total extractives content correlate well with lignin degradation, increase of acid soluble lignin and increased production of ligninolytic enzymes (total peroxidase). Lignin content was determined using FT-NIR spectroscopy as well as by wet-chemical analysis, indicating a very good correlation between the two methods. According to the different analytical methods, the tested fungi can be classified into three categories based on their characteristic behaviour: brown rot, “slow” and “fast” white rot.     

Outbreak of Rhizopus Rot Caused by Rhizopus oryzae on Seedlings of Grafted Cucumber on Pumpkin Rootstock in South Korea

In 2013, an outbreak of Rhizopus rot caused by Rhizopus oryzae occurred in cucumber grafted onto pumpkin rootstock sampled from seedling farms in Changnyeong, South Korea. A water‐soaked appearance of the affected tissue was the first symptom of this soft fungal rot in the seedling stems of grafted cucumber. Lesions at the graft sites softened and rapidly, rotted, and turned brown or dark brown. Measurements and taxonomic characteristics were most similar to R. oryzae. DNA sequencing and phylogenetic analysis of the internal transcribed spacer rRNA gene region confirmed that the isolates were indeed R. oryzae. Koch's postulates were supported by pathogenicity tests conducted on healthy plants. Based on mycological characteristics, pathogenicity test, and molecular analysis, the causal fungus was identified as R. oryzae Went & Prinsen Geerligs. To our knowledge, this is the first report of Rhizopus rot caused by R. oryzae in seedlings of grafted cucumber on pumpkin rootstock in South Korea.     

Reactions of six cultivars of rice (Oryza sativa L.) to three fungal diseases

Abstract

Fungal diseases are the most important threat for rice production in the world. Rice fields were visited and sampled from diseased bushes to identify fungal diseases in Kohgiluyeh and Boyer-Ahmad province, in the south-west of Iran. Fungi were isolated from diseased tissues by Agar-plate method, and purified by single-spore or hyphal-tip methods. They were identified by studying morphological characteristics. The virulence of isolated fungi was evaluated on six dominant rice cultivars, Champa of temperate region, Champa of subtropical region, Gerdeh, Shamim, Fajr and Tarom, under greenhouse conditions. The experiment was set up in a factorial experiment in completely randomized design with four replicates. The incidence of three fungal diseases: brown spot caused by Curvularia australiensis and Bipolaris cookei, foot rot caused by Fusarium globosum and Fusarium sambucinum, and black root rot caused by Exserohilum pedicellatum, was proven in this study. Although, all of the tested cultivars significantly showed different reaction to these fungi, but the cultivars Champa of subtropical region and Tarom were resistant to foot rot as well as the black root rot and the cultivar Gerdeh was resistant to brown spot disease.     

Fungi Associated with Foot Rots on Winter Wheat in Northwest Italy

In a 3-year survey on bread and durum wheat grown in Northwest Italy, brown root rot was the most important disease of the basal part of culm. Year, wheat-growing area, cultivar and their interactions significantly influenced brown root rot incidence. The most important fungal species isolated from lower stems with browning were Microdochium nivale, Drechslera sorokiniana, Fusarium avenaceum, F. graminearum, and F. culmoniliforme, and Pythium spp. were frequently isolated. F., crookwellense was also isolated. Sharp eyespot was a frequent disease; take-all and eyespot occurred only occasionally.     

Antimicrobial Activity of 3-Phenylimidazolidine-2,4-diones and Related Compounds

The structure-activity relationships of 3-(3′,5′-dichlorophenyl)imidazolidine-2,4-dione derivatives were investigated by the agar dilution method using Sclerotinia sclerotiorum as a test microbe. Several compounds were tested for antimicrobial spectrum in vitro with other pathogenic microbes and for foliage protective activity in green house tests with rice sheath blight, rice brown spot, damping-off of cucumber and kidney bean stem rot. It was found that the antimicrobial activity was enhanced when the 1-position of imidazolidine ring was substituted by an alkyl group but was reduced when the 5-position was substituted by alkyl groups. Generally, 3-(3′,5′-dichlorophenyl)imidazolidine-2,4-dione derivatives were active against Scierotiniaceae, Corticiaceae, Dematiaceae, Polystigmataceae or Pleosporaceae. In green house tests, some of these compounds showed high protective activity against rice sheath blight, rice brown spot, damping-off of cucumber and kidney bean stem rot. Results of the green house tests on the above mentioned diseases correlate well with those of in vitro tests except in the case of kidney bean stem rot.     

水稻黑条矮缩病传毒昆虫的防治实践与研究

水稻黑条矮缩病 (RBSDV)是由传毒媒介灰飞虱Laodelphaxstriatellus (Fall n)传播所致 ,治虫防病是目前防治水稻黑条矮缩病的重要手段。生产实践证明 ,防治该病应以控制灰飞虱种群数量增长为首选目标 ,把带毒灰飞虱尽可能地扑灭在迁移到水稻秧苗进行传毒侵染之前。因此掌握防治适期 ,选用高效低毒农药 ,切断初次侵染来源 ,才能达到控制该病发生的目的。     

Build-up of tomato brown root rot caused by Pyrenochaeta lycopersici Schneider and Gerlach

The incidence in unheated glasshouses of tomato brown root rot (BRR) was recorded on five successive crops starting with the first ever grown on the experimental site. In the protected environment the changes followed a pattern that was defined mathematically, the regression linking angular or logit transforms of per cent BRR, observed at different intervals after planting, accounting for c. 72% of the variation. Rates of build-up, seemingly related to initial amounts of inocula, increased in successive seasons, there being more BRR in the fifth season than in the first. Four per cent BRR recorded 5 weeks after planting increased threefold during the next 3 months to 12 %, but in later years, when amounts of early-season infection were doubled to 8%, the incidence of root rot subsequently increased five times. Tomato roots colonized by Pyrenochaeta lycopersici either brown and rot or become corky. The proportion of end-of-season BRR attributable to corkiness increased from the first to fifth seasons. The monthly increments of fruit yield were inversely proportional to the incidence of BRR.     

The Potential Efficacy of Glycyrrhizic Acid and Its Nanostructure Against Brown Rot of Peach fruits

Production of peaches (Prunus persica (L.) Batsch) for both local market and export is increasing each year in Egypt. Brown rot disease, caused by Monilinia laxa and Monilinia fructigena, is considered one of the most important postharvest rots affecting peaches in Egypt and economic losses are increasing. Antifungal activity of glycyrrhizic acid nanoparticles (GA-NPs) and glycyrrhizic acid (GA) at 0.2 and 0.4 mmol/L was investigated as a control for both these brown rot pathogens on peach fruits in both in vitro and in vivo studies. In the in vitro studies, GA-NPs were the most effective as shown by the ability to decrease linear growth of both brown rot pathogens in potato dextrose agar (PDA) amended with 0.4 mmol/L GA-NPs. Micrographs of M. fructigena exposed to 0.4 mmol/LGA showed mycelial deformations, nodule formation, detachment of the cell wall, shrinkage and inhomogeneous cytoplasmic materials with large vacuoles. Mycelium of M. laxa exposed to 0.4 mmol/ LGA-NPs resulted in thinner and distorted hyphae, nodule formation, cell wall thinning, and swellings. The GANPs and GA treatments improved fruit quality by maintaining firmness and total soluble solids (TSS). GA-NPs were more effective in decreasing decay incidence than their bulk material. The 0.4 mmol/L GA-NPs completely inhibited the disease on naturally infected peach fruits for both seasons of 2018 and 2019. Furthermore, 0.4 mmol/L GA-NPs reduced the disease incidence in inoculated fruits by 95 (M. laxa) and 88% (M. fructigena) in 2018 season and 96 (M. laxa) and 85% (M. fructigena) in 2019 season. In conclusion, GA-NPs could enhance the resistance of peaches against brown rot caused by M. laxa and M. fructigena.     

Fusarium incarnatum is associated with postharvest fruit rot of muskmelon (Cucumis melo)

Postharvest fruit rot was observed on muskmelon (Cucumis melo) on market shelves at a melon farm in the city of Hatyai, Songkhla, Thailand. Diseased muskmelon fruit displayed cotton-like mycelia on wounds and had brown to dark brown internal tissue. Based on morphological characteristics and molecular analysis of internal transcribed spacer (ITS) and translation elongation factor 1-α (TEF1-α) DNA sequences, the fungal pathogen was identified as Fusarium incarnatum. This species belongs to the Fusarium incarnatum-equiseti species complex (FIESC). A pathogenicity test was conducted to verify Koch's postulates, and F. incarnatum was observed to cause fruit rot on muskmelon; symptoms of the disease were similar to those seen in the field. However, only artificially wounded melons became infected, suggesting that F. incarnatum is an obligate wound-infecting pathogen. To our knowledge, this is the first report of F. incarnatum causing fruit rot of muskmelon in Thailand.