Changes in biochemical constituents of paddy straw during degradation by white rot fungi and its impact on in vitro digestibility

Aims: To improve the digestibility of paddy straw to be used as animal feed by means of selective delignification using white rot fungi. Methods and Results: Solid state fermentation of paddy straw was carried out with some white rot fungi for 60 days. Different biochemical analyses, e.g. total organic matter (TOM) loss, hemicellulose loss, cellulose loss, lignin loss and in vitro digestibility, were carried out along with laccase, xylanase and carboxymethyl cellulase activity. The results were compared with that of a widely studied fungus Phanerochaete chrysosporium, which degraded 464 g kg^?1 TOM and enhanced the in vitro digestibility from 185 to 254 g kg^?1 after 60 days of incubation. Straw inoculated with Phlebia brevispora possessed maximum crude protein. Conclusions: All the tested white rot fungi efficiently degraded the lignin and enhanced the in vitro digestibility of paddy straw. Phlebia brevispora, Phlebia radiata and P. chrysosporium enhanced the in vitro digestibility almost to similar levels, while the loss in TOM was much lesser in P. brevispora and P. radiata when compared to P. chrysosporium. Significance and Impact of the Study: The study reflects the potential of P. brevispora and P. radiata as suitable choices for practical use in terms of availability of organic matter with higher protein value, selective ligninolysis and better digestibility.     

Factors influencing in the response of <i>Schizolobium parahybum</i> (Vell) Blake to <i>Ceratocystis paradoxa</i> and <i>C. moniliformis</i>

In the Ecuadorian coast one of the most destructive diseases of the pachaco is vascular wilt or stem rot caused by Ceratocystis complex, so the aim of this study was to determine the factors that affect the efficiency of the reaction of bark pachaco to this disease. This research was conducted under laboratory conditions, using trees pachaco S38, S41, S98, AE-1, AE-2 and AE-3, and pathogenic species Ceratocystis paradoxa and C. moniliformis. The method utilized was tissue stem bark,with bark sections with 4.5 cm², and a suspension of 3x10⁴ units infection and remained in a humid chamber for 96 hours at 25 ± 5 °C. Were determined grades of resistance/ susceptibility using a scale from 0 to 4, depending on the amount of mycelia and peritecio in each plant sample. Three factors were used: four colonies obtained by several transfers from each fungal specie, four ages of colonies of each fungal specie and four volumes of inoculum applied (units of infection), using for each experiment separately Completely Randomized Design with 4 replications factorial arrangement. For comparison between treatment means was used Tukey test at 5% probability of error. For future trials using this technique, you could use 30-day colonies for C. paradoxa and 40 days for C. moniliformis, and an application volume of 100 μL/cm², it would improve the level of response for the formation of perithecium and mycelia in samples cortex.     

软腐白菜细菌群落结构多样性与生长环境的相关性

[目的]通过对比分析不同生境白菜软腐病变组织与根系土壤相关细菌的群落结构,探讨白菜软腐细菌种群的多样性,以及与生境土壤细菌种群的相关性.[方法]样品采自河南省2个不同生态型白菜田,以成熟白菜软腐组织及病株根系土壤为目标,利用模拟原环境的培养基成分和条件,对样品中的细菌进行高通量分离培养和细胞16S rRNA基因序列比对分析,获得各样品细菌种群结构及其丰度,进而对各样品的优势菌群进行对比分析.[结果]两种不同生境白菜软腐组织细菌总量M05T为4.0×l0s cell/g、Q2T为1.2×1011 cell/g,分别获得纯菌56株和85株.M05T优势菌为萎蔫短小杆菌萎蔫亚种(Curtobacterium flaccunfaciens pv.Flaccumfaciens);Q2T优势菌为假单胞菌(Pseudomonas spp.)(柄木槿假单胞菌(P.hibiscicola)、台湾假单胞菌(P.taiwanensis)、托木尔假单胞菌(P.tuomuerensis)、莫塞尔假单胞菌(P.mosselii)).根系土壤细菌总量M05S为2.7 × 105 cell/g、Q2S为6.2 × 107 cell/g,分别获得纯菌36株和70株.M05S优势菌为巨大芽胞杆菌(Bacillus megatherium);Q2S优势菌为假单胞菌(Pseudomonas spp.)(香鱼假单胞菌(P.plecoglossicida)、栖木槿假单胞菌(P.hibiscicola)、类黄色假单胞菌(P.parafulva)、蒙氏假单胞菌(P.monteilii)、膝形假单胞菌(P.geniculata)).[结论]依据不同生境的白菜软腐组织和根系土壤细菌群落结构对比分析,认为白菜软腐菌可能具有多样性和多种致病来源,本研究为软腐病多种防治措施的制定提供基础研究和菌种资源.     

Uptake of cadmium ions in white-rot fungus Trametes versicolor: effect of cd (II) ions on the activity of laccase

The effects of cadmium Cd (II) ions on the physiology and biological activity of Trametes versicolor, a strain belonging to white-rotting Basidiomycetes, were examined. Cd (II) ions were added to 10-day-old cultures grown on a liquid medium, or at the time of inoculation. Our experiments showed that T. versicolor is a good cadmium biosorbent from aqueous solution, this strain removing almost all the Cd (ll) ions over the first 2h of incubation by what appears to be a rapid, energy-independent surface binding phenomenon, at the rate of approximately 2mg Cd per g mycelial dry weight. An additional slower and energy-dependent transport mechanism was also present, taking in approximately 0.3mg Cd (II) perg dry weight. It is also shown that these Cd (II) ions significantly stimulate the activity of extracellular laccase when added to 10-day-old cultures.     

Influence of the endomycorrhizal fungus Glomus mosseae on the development of peanut pod rot disease in Egypt

Glomus mosseae and the two pod rot pathogens Fusarium solani and Rhizoctonia solani and subsequent effects on growth and yield of peanut (Arachis hypogaea L.) plants were investigated in a greenhouse over a 5-month period. At plant maturity, inoculation with F. solani and/or R. solani significantly reduced shoot and root dry weights, pegs and pod number and seed weight of peanut plants. In contrast, the growth response and biomass of peanut plants inoculated with G. mosseae was significantly higher than that of non-mycorrhizal plants, both in the presence and absence of the pathogens. Plants inoculated with G. mosseae had a lower incidence of root rot, decayed pods, and death than non-mycorrhizal ones. The pathogens either alone or in combination reduced root colonization by the mycorrhizal fungus. Propagule numbers of each pathogen isolated from pod shell, seed, carpophore, lower stem and root were significantly lower in mycorrhizal plants than in the non-mycorrhizal plants. Thus, G. mosseae protected peanut plants from infection by pod rot fungal pathogens. Accepted: 10 February 2000     

假单胞菌YL11对扩展青霉的抑制作用及其机理初探

【背景】苹果青霉病是由扩展青霉引起的一种重要的果实采后病害,影响果实品质导致苹果腐烂从而造成经济损失。【目的】研究假单胞菌YL11对扩展青霉的抑制作用和苹果采后青霉病的防治效果,并对抑菌机理进行初步探讨。【方法】以扩展青霉为供试菌株,研究不同浓度的假单胞菌YL11无菌发酵液对扩展青霉菌落直径、孢子萌发率、菌丝体干重、苹果损伤接种病斑直径扩展的影响,利用对电导率、核酸及蛋白释放量、AKP含量、SDH活性、ATP酶活性和ATP含量的影响对抑菌机理进行探究。【结果】假单胞菌YL11无菌发酵液能有效抑制扩展青霉生长,抑菌圈直径为22.33±0.27 mm,抑菌效价为71.67 mm/mL;能有效抑制孢子萌发,100%无菌发酵液对孢子萌发抑制率达到80.2%;对扩展青霉的生物量也有一定抑制作用,体积分数为100%时,菌丝体干重为4.7mg/mL,抑制率达到39.74%;无菌发酵液处理能有效抑制苹果青霉病病斑的扩展,3d时对病斑扩展的抑制率最大,达到47.1%;无菌发酵液处理均能引起电导率升高、胞内核酸和蛋白释放量增大、胞外AKP含量升高、SDH活性降低、ATP酶活性和ATP含量均降低,且随着发酵液浓度的增加效果越明显。【结论】假单胞菌YL11能显著抑制扩展青霉的生长,破坏细胞膜结构、降低能量代谢酶活性,从而扰乱扩展青霉的正常生长,对苹果青霉病有较好的生防效果,具有潜在的开发价值。     

青稞根腐病对根际土壤微生物及酶活性的影响

选取甘肃省卓尼县青稞种植区为研究地点,调查青稞根腐病的发病情况,并分别采集其健康植株和发病株根际的土壤,对比分析其土壤微生物生物量(碳、氮、磷)、微生物数量(细菌、真菌、放线菌)以及过氧化氢酶、蔗糖酶、脲酶、碱性磷酸酶、纤维素酶5种酶活性。结果发现,研究区10个采样点均有青稞根腐病的发生,发病率在5%—20%之间,不同地点发病率不同。根腐病的发生,会显著影响青稞根际微生物生物量,导致微生物生物量碳、氮、磷的含量发生变化,其中微生物生物量氮和磷含量整体降低,且不同采样点微生物量不同。土壤微生物数量总体呈现细菌放线菌真菌的趋势,但不同微生物对根腐病发病的响应不同,细菌和放线菌数量因根腐病的发生而减少,真菌的数量则增多;不同采样点土壤微生物数量不相同,细菌和真菌呈现区域性特征,放线菌的数量不呈现地域性。根腐病的发生还造成土壤酶活性的改变,其中蔗糖酶、脲酶、磷酸酶的含量因根腐病的发生而降低,而纤维素酶则升高,过氧化氢酶的变化没有规律。总而言之,根腐病的发生会使青稞根际土壤微生物组成发生改变,碳、氮、磷等物质代谢受到抑制,而能量代谢发生紊乱。因此,研究和防治青稞根腐病就必须重视土壤微生物及土壤酶的作用。     

玉米种质和新品种对腐霉茎腐病和镰孢穗腐病的抗性分析

玉米是我国最重要的农作物之一,腐霉茎腐病和镰孢穗腐病是玉米生产上的重要病害。2006-2012年期间,对1647份玉米种质进行了抗肿囊腐霉茎腐病和拟轮枝镰孢穗腐病鉴定,筛选出高抗茎腐病和穗腐病的种质分别为564份和27份,占鉴定总材料的34.2%和1.6%,抗性材料分别为209份和352份,占比为12.7%和21.4%,表明高抗肿囊腐霉茎腐病的资源较为丰富,高抗镰孢穗腐病的种质相对匮乏。其中,13份种质对2种病害均表现高抗,207份种质对2种病害均表现抗性或对其中一种表现高抗而另一种表现抗性。自交系中对肿囊腐霉茎腐病和拟轮枝镰孢穗腐病表现抗性以上(含HR和R)的种质分别占总鉴定种质的56.5%和23.6%,在农家种中分别为21.2%和21.4%,表明玉米自交系中的抗性资源较农家种丰富。2009-2013年期间参加国家玉米区试的品种中,对腐霉茎腐病表现高抗、抗性、中抗、感病和高感的品种分别占11.5%、11.9%、40.1%、17.6%和18.9%。2009-2011年间,中抗以上的育成品种所占比例呈现明显上升趋势,但2012-2013年间,中抗以上的品种所占比例呈下降趋势。     

A new clade of Dickeya spp. plays a major role in potato blackleg outbreaks in North Finland

Until recently Dickeya was regarded as a pathogen not established in Finland. As a result the blackleg symptom observed on potato was often associated with Pectobacterium atrosepticum. The occurrence of Dickeya spp. on potato in Finland was first reported in 2004. Since then the prevalence of Dickeya has been monitored through surveys and routine test of seed lots produced in the country. The results of monitoring of Dickeya spp. in seed lots produced in Finland between the years 2004 and 2008 indicated a steady increase in the incidence of Dickeya spp. The highest incidence was observed in samples from the 2006 growing season where about 37% were positive for Dickeya spp. The summer in 2006 was one of the warmest summers recorded in 100 years in Finland. The majority of infected lots were imported varieties. Since recently heavy blackleg outbreaks have occurred in production fields in the High Grade (HG) zone. A detailed study of these incidents of blackleg outbreaks in North Finland during the years 2008 and 2010 indicated that Dickeya spp. was the major component in the observed blackleg complex. It was detected and isolated from almost all symptomatic plants investigated. Repetitive sequences PCR (REP‐PCR) and Pulsed Field Gel Electrophoresis (PFGE) analysis of strains isolated in Finland showed identical pattern with those isolated recently in other European countries with a proposed name ‘Dickeya solani’. Moreover, the dnaX gene sequence of the representative strains isolated in Finland indicated 100% similarity to the dnaX sequences of ‘D. solani’. The study presents the first report of a detailed analysis of bacteria involved in potato blackleg complex from natural field outbreaks in North Finland HG zone and characterisation of the ‘D. solani’ strains playing the major role in the disease complex.     

Biotransformation of linear alkylbenzene sulfonate (LAS) by Phanerochaete chrysosporium: oxidation of alkyl side-chain

The white rot fungus Phanerochaete chrysosporium, which generally mineralizes substituted aromatics to CO₂, transformed linear alkylbenzene sulfonate (LAS) surfactants mainly at their alkyl side chain. Degradation of LAS was evidenced by a zone of clearing on LAS-containing agar plates and colorimetric analysis of liquid cultures. Disappearance of LAS was virtually complete within 10 days in low nitrogen (2.4 mM N), high nitrogen (24 mM N) and malt extract (ME) liquid media. After 5 days of incubation in ME medium, transformation of LAS was complete at concentrations4 mg l^-1, but decreased at higher concentrations. The LAS degradation was not dependent on lignin peroxidases (LiPs) and manganese-dependent peroxidases (MnPs). Mineralization of¹⁴C-ring-LAS to ¹⁴CO₂ by P. chrysosporium was <1% regardless of the culture conditions used. Thin layer chromatography and mass spectral analyses indicated that P. chrysosporium transformed LAS to sulfophenyl carboxylates (SPCs) through oxidative shortening of the alkyl side-chains. While LAS disappearance in the cultures was not dependent on LiPs and MnPs, transformation of the parent LAS moieties to SPCs was more extensive in low N medium that favors expression of these enzymes. The SPCs produced in LN cultures were shorter in chain-length than those produced in ME cultures. Also there was a notable shift in the relative abundance of odd and even chain length metabolites compared to the starting LAS particularly in the low N cultures suggesting the possible involvement of processes other than or in addition to-oxidation in the chain-shortening process.