The effect of Trichoderma harzianum and T. koningii on the control of tan spot (Pyrenophora tritici-repentis) and leaf blotch (Mycosphaerella graminicola) of wheat under field conditions in Argentina

The effect of six isolates of Trichoderma harzianum and one isolate of T. koningii on the incidence and severity of tan spot (Pyrenophora tritici-repentis) and leaf blotch of wheat (Mycosphaerella graminicola) was evaluated under field conditions. Significant differences between wheat cultivars, inoculum types and growth stages were found. Three of the isolates tested (T2 for M. graminicola, T7 for P. tritici-repentis and T5 for both of them) showed the best performance in controlling leaf blotch and tan spot when coated onto seed or sprayed onto wheat leaves at different growth stages, with significant severity reduction up to 56%. At tillering, six of the isolates reduced the severity of P. tritici-repentis and M. graminicola compared to the control by up to 39% and 12-53%, respectively. In some experiments, the biocontrol preparation (T2 and T5) gave a level of disease control similar to that obtained with Tebuconazole (70 and 48%, respectively). The effect of Trichoderma against P. tritici-repentis was also observed at the heading stage, when six of the treatments reduced disease severity by 16-35%. This is the first report on the efficacy of Trichoderma spp. against wheat necrotrophic pathogens under field conditions in Argentina.     

不同栽植密度对斑叶稠李苗木培育质量的影响

以斑叶稠李（Padus maackii）1年生苗木为研究对象,通过4种不同栽植密度（60、80、100、120 株·m^-2）试验,测定其苗木形态、生物量、光合速率及养分含量,旨在探明不同密度对斑叶稠李苗木生长及养分含量的影响,为其高质量苗木培育提供理论依据。结果表明：（1）栽植密度显著影响苗木生物量,各密度下苗木根、茎、叶生物量由大到小顺序均为80 株·m^-2 > 60 株·m^-2 > 100 株·m^-2 > 120 株·m^-2;60和80 株·m^-2密度下斑叶稠李苗木质量指数显著高于100和120 株·m^-2密度处理。（2）栽植密度显著影响苗木侧根数,在80 株·m^-2的密度下达到最大;（3）80 株·m^-2密度较其它密度显著提高了苗木氮、磷、钾养分含量。（4）叶生物量、根生物量和侧根数与苗木各质量指标间Pearson相关性系数均达到了显著水平（P<0.1）,而光合速率和主根长与苗木各质量指标均不相关（P>0.1）。综合以上结果,斑叶稠李1年生苗木最适栽植密度为80 株·m^-2,且密度处理主要影响斑叶稠李苗木叶生物量、侧根数及根生物量指标,进而影响苗木质量。     

The influence of circulation frequency on fungal morphology: a case study considering Kolmogorov microscale in constant specific energy dissipation rate cultures of Trichoderma harzianum

The energy dissipation/circulation function (EDCF) is the product of the specific energy dissipation rate in the impeller swept volume (P/kD³) and the frequency of particle circulation (1/t_c) through that volume. A direct relationship between mycelial fragmentation and EDCF has been reported. However, and although hyphal fragmentation is assumed to occur by hyphae-eddy interaction, Kolmogorov microscale (λ) has not been shown to determine, at least directly, fungal morphology. In this work we studied the influence of λ and EDCF evolution, as well as the individual effects of P/kD³ and 1/t_c, on Trichoderma harzianum cultures in an attempt to elucidate the mechanistic interactions between parameters. T. harzianum cultures, conducted at equivalent yielding P/kD³ conditions, were developed using two different Rushton turbines diameter sets. For the studied conditions, 1/t_c had a greater effect over mycelial clump size and growth rate than P/kD³. Consequently, broth viscosity, and hence Kolmogorov microscale, was a function of impeller diameter, even among cultures operated at equivalent specific energy dissipation rates. The latter could partially explain why Kolmogorv's theory has not been able to fully correlate morphological data, and highlights the importance of 1/t_c on fungal bioprocesses. A theoretical approach to monitor λ in large-scale bioreactors is proposed.     

Augmentation of Soil with Sporangia of Actinoplanes spp. for Biological Control of Pythium Damping-off

A method was developed for applying strains of Actinoplanes spp. that are hyper-parasites of oospores of Pythium ultimum to soil for reducing Pythium damping-off of plants. The method is based on the augmentation of soil with sporangia of a strain of Actinoplanes spp. borne on clay granules. In vitro sporulation of strains K30, W57, W257 and 25844 was: (1) greater for most strains on dilute Czapek-Dox agar than on four other agar media; (2) inhibited by continuous exposure to fluorescent light of intensity 4-150 μEm^-2s^-1, but not by exposure to 1 μEm^-2s^-1 or darkness; (3) greater at 20-307deg;C than at 10°C;and (4) greater at pH 6-7 than at pH 5 or 8. On solid carriers treated with dilute Czapek-Dox broth (pH 7) and incubated in the dark at 30°C for 3 weeks, strains sporulated poorly or not at all on vermiculite, perlite and rice hulls, but sporulated abundantly (10⁷-10⁹ colony-forming units (CFU) g^-1 of granules) on montmorillonite clay granules. When strains 25844, W57 and W257 were applied as granules (4 10⁷ - 4 × 10⁸ CFU g^-1) at 5% (w/w) to field plots infested with 750-1000 oospores of P. ultimum g^-1 of soil, only strain 25844 consistently increased emergence and reduced root rot of table beets 8- 1 at 24-28 days after planting compared with controls. Strain 25844 (10⁸ CFU g^-1 of granules) at 1% (w/w) also increased the emergence of bush beans at 28 days after planting in P. ultimum-infested plots, but lower rates were ineffective. The inoculum viability of strain 25844 on clay granules declined 100-fold during 2 months of storage at 5-35°C, but thereafter remained stable for another 4 months. Strain 25844 on 6-month-old granules retained a high degree of hyper-parasitic activity toward oospores of P. ultimum. Augmentation of field soil with sporangia of Actinoplanes spp. is a valid approach to the biological control of pythium damping-off.     

滇中亚高山人工林凋落物分解对模拟氮沉降的响应

2018年2月至2019年1月,利用尼龙网袋法对滇中亚高山华山松和云南松两种人工林开展模拟氮(N)沉降下凋落叶和凋落枝原位分解试验,N沉降水平分别为对照(CK, 0 g N·m^-2·a^-1)、低N(LN, 5 g N·m^-2·a^-1)、中N(MN, 15 g N·m^-2·a^-1)和高N(HN, 30 g N·m^-2·a^-1)。结果表明: 华山松凋落叶和凋落枝年分解率分别为34.8%和18.0%,分别高于云南松凋落叶的32.2%和凋落枝的16.1%。模拟N沉降下,LN处理使华山松凋落叶、枝分解95%所需时间较对照分别减少0.202和1.624年,MN处理分别减少0.045和1.437年,HN处理则分别增加0.840和2.112年;LN处理使云南松凋落叶、枝分解95%所需时间较对照分别减少0.766和4.053年,MN处理分别增加0.366和0.455年,HN处理分别增加0.826和0.906年。经过1年的分解,低N处理促进了华山松和云南松凋落物(叶、枝)的分解,而高N处理表现为抑制作用;N沉降对两种林型凋落物分解的影响与凋落物中纤维素和木质素含量密切相关。可见,凋落物基质质量在一定程度上决定了凋落物分解对N沉降的响应情况,尤其是纤维素和木质素含量。     

外源氮添加对温带荒漠地表凋落物分解及养分释放的影响

采用分解网袋法,在古尔班通古特沙漠南缘设置对照N₀(0 g N·m^-2·a^-1)、N₅(5 g N·m^-2·a^-1)、N₁₀(10 g N·m^-2·a^-1)和N₂₀(20 g N·m^-2·a^-1)4个施N处理,研究外源N添加对多枝柽柳、盐角草及两者混合凋落物分解过程及养分释放的影响,分析氮沉降对荒漠生态系统凋落物分解的影响。结果表明: 各物种凋落物的分解速率存在显著差异,经过345 d的分解,多枝柽柳、盐角草及混合物在不同N处理间的分解速率分别为0.64～0.70、0.84～0.99和0.71～0.81 kg·kg^-1·a^-1。凋落物分解过程中,N、P均表现为养分的直接释放,试验结束时,N₀、N₅、N₁₀和N₂₀处理单种凋落物及其混合物N分别释放60.6%～67.4%、56.7%～62.6%、57.4%～62.3%、46.8%～63.0%,P分别释放51.9%～77.9%、59.9%～74.7%、53.0%～79.9%、52.3%～76.4%。N处理对单种凋落物及其混合物的分解影响不显著,但各种凋落物的养分动态对N添加的响应不同,N处理抑制了盐角草N、P释放及混合凋落物P释放,而对多枝柽柳无影响。在温带荒漠,适量的N输入对凋落物分解速率影响不大,但可能会延缓个别物种养分向土壤系统的归还。     

Bench-scale fermentation of Trichoderma viride on wastewater sludge: Rheology, lytic enzymes and biocontrol activity

Conidiation and lytic enzyme production by Trichoderma viride at different solids concentration of pre-treated municipal wastewater sludge was examined in a 15-L fermenter. The maximum conidia concentration (5.94 × 10⁷ CFU mL⁻¹ at 96 h) was obtained at 30 g L⁻¹ suspended solids. The maximum lytic enzyme activities were achieved around 12–30 h of fermentation. Bioassay against a fungal phytopathogen, Fusarium sp. showed maximum activity in the sample drawn around 96 h of fermentation at 30 g L⁻¹ suspended solids concentration. Entomotoxicity against spruce budworm larvae showed maximum value ≈17290 SBU μL⁻¹ at 30 g L⁻¹ suspended solids concentration at the end of fermentation (96 h). Plant bioassay showed dual action of T. viride, i.e., disease prevention and growth promotion. The rheological analyses of fermentation sludges showed the pseudoplastic behaviour. In order to maintain required dissolved oxygen concentration ≥30%, the agitation and aeration requirements significantly increased at 35 g L⁻¹ compared to 30 and 25 g L⁻¹. The oxygen uptake rate and volumetric oxygen mass transfer coefficient, k_La at 35 g L⁻¹ did not increase in comparison to 30 g L⁻¹ due to rheological complexity of the broth during fermentation. Thus, the successful fermentation operation of the biocontrol fungus T. viride is a rational indication of its potential for mass-scale production for agriculture and forest sector as a biocontrol agent.     

Media and Fermentation Processes for the Rapid Production of High Concentrations of Stable Blastospores of the Bioinsecticidal Fungus Paecilomyces fumosoroseus

In shake flask and fermentor studies, various media components and culture inocula were tested to improve P. fumosoroseus spore production rates, yield and stability. To evaluate inoculum potential and inoculum scale-up for fermentor studies, conidia and liquid culture-produced spores of various strains of P. fumosoroseus were compared as inoculum. Inoculation of liquid cultures with blastospores at concentrations of at least 1×10⁶ spores mL^-1 resulted in the rapid production of high concentrations of blastospores (∼1×10⁹ spores mL^-1, 48 h fermentation time) for all strains tested. The rapid germination rate of blastospores (90% after 6 h incubation) compared to conidia (>90% after 16 h incubation) and the use of higher inoculum rates reduced the fermentation time from 96 to 48 h for maximal spore yields. A comparison of various complex nitrogen sources showed that liquid media supplemented with acid hydrolyzed casein or yeast extract supported the production of high concentrations of blastospores that were significantly more desiccation-tolerant (79-82% survival after drying) when compared to blastospores produced in media supplemented with other nitrogen sources (12-50% survival after drying). For rapid spore production, requirements for trace metals and vitamin supplementation were dependent on the type of hydrolyzed casein used in the medium. Fermentor studies with two strains of P. fumosoroseus showed that high concentrations (1.3-1.8×10⁹ spores mL^-1) of desiccation-tolerant blastospores could be produced in 48-h fermentations. These studies have demonstrated that the infective spores of various strains of the fungal bioinsecticide Paecilomyces fumosoroseus can be rapidly produced using deep-tank, liquid culture fermentation techniques.     

黄土丘陵区刺槐和侧柏人工林树干液流特征及其对降水的响应

水分供应不足及水热不同步常导致黄土丘陵地区在春末和夏初出现季节性干旱。为阐明该地区主要造林树种的蒸腾耗水特征及其对降水的响应, 使用热扩散式树干茎流计(TDP)于2009年4-10月对黄土丘陵区安塞国家生态试验站刺槐(Robinia pseudoacacia)和侧柏(Platycladus orientalis)的树干液流密度(F_d)进行连续观测, 并同步测定了气象、土壤水分等环境因子。结果表明: 刺槐和侧柏在生长季内不同生长时期的F_d均表现为单峰型日变化特征, 刺槐最高液流峰值为0.12068 m³·m^-2·h^-1, 是侧柏最高液流值(0.03737 m³·m^-2·h^-1)的3.23倍。除生长旺盛季(7-8月)外, 刺槐和侧柏降水后的F_d明显高于降水前。同时反映水汽压差(VPD)和太阳辐射(R_s)的蒸腾变量(VT)能够很好地模拟F_d, 且两者呈显著的指数正相关关系, 随VT的增加F_d逐渐增大, VT增加到50 kPa (W·m^-2)^1/2左右时, F_d的变化趋于稳定; 通过对降水前后两个树种水力导度(拟合参数b值)分析, 相对于侧柏, 刺槐更易受降水的影响(p < 0.001)。因此, 可认为刺槐是降水敏感型植物, 而侧柏是降水不敏感型植物。该研究通过分析黄土丘陵区人工林树种对降水的差异性响应, 从树木水分利用方面能够为当地生态恢复过程中人工林的管理提供科学依据。     

Effect of Trichoderma harzianum on perithecial production of Gibberella zeae on wheat straw

Conidial suspensions and cell-free filtrates of Trichoderma harzianum isolates were evaluated for their effectiveness in reducing perithecial and ascospore production of Gibberella zeae on wheat straw. Isolate T-22, which is registered in the US as a biological control agent (Plant Shield™), was included in the study as a positive control. When co-inoculated with G. zeae all 11 isolates of T. harzianum significantly reduced perithecial numbers on wheat straw. Five T. harzianum isolates, including T-22, reduced perithecial formation by 70% or greater. All isolates of G. zeae, varied in their ability to produce perithecia. Isolate 192132 produced the greatest number of perithecia and was used to further evaluate the effect of application time of the T. harzianum isolates. Perithecial reduction was highest (96-99%) when T. harzianum conidial suspension or cell-free filtrate was applied to straw 24 h prior to inoculation with G. zeae. Control was less effective when T. harzianum was applied at the same time (co-inoculated) or 24 h after G. zeae. Treatments which reduced perithecial numbers also reduced ascospore numbers; however, the average numbers of ascospores per perithecia were not significantly lowered. Field trials showed significant reduction of perithecia on residues treated with T. harzianum prior to placement on the soil surface. Both T. harzianum and G. zeae were re-isolated from residues sampled in July and August after 30 and 60 days of exposure to the environment.     

不同土壤含水量下侧柏幼树叶片水分利用效率

对植物水分利用效率的研究,可以揭示植物的内在耗水机制,为区域森林生态系统经营与维护提供依据.本研究以侧柏幼树为研究对象,通过室内控制试验设置不同的土壤水分梯度,分别用气体交换法和稳定同位素法对其不同土壤含水量条件下的瞬时水分利用效率(WUE_gs)和短期水分利用效率(WUE_cp)进行研究.结果表明:受气孔导度(g_s)的影响,叶片净光合速率(P_n)和蒸腾速率(T_r)随土壤含水量的增加呈现相同的变化趋势,均在土壤含水量为70%～80%田间持水量(FC)时达到最大值;叶片WUE_gs则在土壤含水量最低(35%～45% FC)时达到最大值(7.26 mmol·m^-2·s^-1).叶片可溶性糖、枝条韧皮部渗出液的δ¹³C都在土壤含水量最低(35%～45% FC)条件下达到最大值,且叶片可溶性糖的δ¹³C明显高于枝条韧皮部渗出液的δ¹³C,未产生明显分馏;而叶片WUE_cp也在土壤含水量最低(35%～45% FC)时达到最大值(7.26 mmol·m^-2·s^-1).相同条件下,叶片WUE_gs和WUE_cp存在一定差异(平均相差0.52 mmol·m^-2·s^-1),WUE_gs时空变异性较大,而WUE_cp更具有代表性.侧柏幼树通过降低生理生态活动和提高水分利用效率来适应干旱的土壤条件.     

木霉对月季幼苗生长的影响

为了研制促进月季生长的木霉生防菌肥，采用本实验室分离鉴定的哈茨木霉T6施于月季盆栽土壤中，分析木霉菌对"十姐妹"月季硬枝扦插发芽、幼苗生长、防御酶活性和内源激素水平的影响。结果表明：施用哈茨木霉T6的月季硬枝出芽率和幼苗枝条长度分别是对照的1.4和1.82倍；并且枝条和叶的干重、枝条和叶的含水率均显著增加。此外显著提高了叶中3种防御酶SOD、POD、CAT的活性及6种内源激素IAA、GA₃、ZT、ABA、SA和JA的水平。说明木霉T6具有促进月季生长和提高其抗性的作用，研究结果为研制促进月季生长的生物菌肥提供理论依据。     

Synergistic effects of antagonistic fungi and a plant growth promoting rhizobacterium, an arbuscular mycorrhizal fungus, or composted cow manure on populations of Meloidogyne incognita and growth of tomato

Effects of four antagonistic fungi (Paecilomyces lilacinus, Pochonia chlamydosporia, Trichoderma harzianum and Gliocladium virens) alone and together with a plant growth promoting rhizobacterium Pseudomonas putida, an arbuscular mycorrhizal fungus Glomus intraradices or with composted cow manure (CCM) were assessed on the growth of tomato and on the reproduction of Meloidogyne incognita in glasshouse experiments. Application of all antagonistic fungi (except G. virens), P. putida, G. intraradices or CCM caused a significant increase in the growth of plants without nematodes. However, use of either of these fungi, P. putida, G. intraradices and CCM against plants with nematodes caused a significant increase in tomato growth. Paecilomyces lilacinus caused a 42% increase in the growth of nematode-inoculated plants followed by P. chlamydosporia (36%), T. harzianum (18%) and G. virens (15%). CCM caused about 57% increase in the growth of nematode-inoculated plants followed by P. putida (37%) and G. intraradices (31%). Maximum increase (71%) in the growth of nematode-inoculated plants was observed when CCM was used with P. lilacinus. Moreover, P. lilacinus caused a high reduction (55%) in galling and nematode multiplication, while G. virens the least (25%). Use of P. putida also caused a 39% reduction in galling and nematode multiplication followed by CCM (34%) and G. intraradices (32%). Combined use of CCM with P. lilacinus caused maximum reduction (79%) in galling and nematode multiplication. Re-isolation of antagonistic fungi from nematodes revealed that P. lilacinus parasitised more females and eggs than other antagonistic fungi. Root colonisation by P. putida was increased with P. lilacinus, while colonisation by G. intraradices was reduced in the presence of antagonistic fungi.     

Sap flow characteristics and its responses to precipitation in Robinia pseudoacacia and Platycladus orientalis plantations

Aim In the loess hilly region, drought stress frequently occurs during the late spring and early summer as a result of insufficient water supply and asynchronous changes between temperature and precipitation. Our objective was to quantify the characteristics of water-consumption through transpirations and their responses to precipitation in the dominant plantations in this region. Methods Thermal dissipation probe (TDP) was used to measure the sap flow density (F_d) of Robinia pseudoacacia and Platycladus orientalis from April through October in 2009 in Ansai National Ecological Experimental Station. Environmental variables, including meteorological factors and soil water content, were simultaneously measured. Important findings The diurnal variation of F_d exhibited a single-peak curve during the growing season of R. pseudoacacia and P. orientalis. The maximum F_d was three times greater in R. pseudoacacia (0.12068 m³·m^-2·h^-1) than that in P. orientalis (0.03737 m³·m^-2·h^-1). Except in the rapid-growth season (July to August), the F_d of these two species during the post-precipitation period were significantly higher than that during the pre-precipitation period. The F_d of P. orientalis and R. pseudoacacia was well fitted with transpiration (VT), an integrated index calculated from both vapor pressure deficit (VPD) and solar radiation (R_s), using an exponential saturation function. Generally, F_d increased in response to rising VT, while these values tended to be stable when VT reached about 50 kPa (W·m^-2)^1/2. Furthermore, R. pseudoacacia showed more sensitive to precipitation (p < 0.001) than P. orientalis, according to different hydraulic conductance model coefficients (fitting parameter b) between pre- and post-precipitation periods. Therefore, R. pseudoacacia could be considered as a precipitation-sensitive species, while P. orientalisasa precipitation-insensitive species. Through analyzing the different responses of plantation species to precipitation in the loess hilly region, this study provides a scientific basis for the local plantation management from the aspect of tree water use during ecological restoration.     

Interaction Between the Entomopathogens Beauveria bassiana, Metarhizium anisopliae and Paecilomyces fumosoroseus and the Mycoparasites Clonostachys spp., Trichoderma harzianum and Lecanicillium lecanii

Biocontrol agents of numerous insect pests and fungal pathogens exist but virtually nothing is known about their interaction if used simultaneously. Our objective was to investigate the compatibility of the entomopathogens Beauveria bassiana, Metarhizium anisopliae and Paecilomyces fumosoroseus, and the broad host-range mycoparasites Clonostachys spp., Trichoderma harzianum and Lecanicillium lecanii. In vitro host-range tests revealed that M. anisopliae was highly susceptible to all mycoparasites tested. B. bassiana was attacked by Clonostachys rosea, and P. fumosoroseus. was resistant to mycoparasites. M. anisopliae but not P. fumosoroseus killed nymphs of Bemisia tabaci in bioassays. B. bassiana and M. anisopliae proved lethal to Cosmopolites sordidus, Diatraea saccharalis and Sitophilus oryzae. Coapplication of mycoparasites with entomopathogens did not affect their biocontrol efficacy in vivo, although the reisolation success of entomopathogens could be significantly reduced, especially from smaller insect species. Trichoderma spp. were reisolated from mycoparasite-treated insects more frequently than C. rosea. The coapplication of the highly susceptible M. anisopliae generally enhanced mycoparasite recovery. Mycofungicide preparations caused some insect mortality but less than a copper hydroxide fungicide which is still permissible in organic agriculture. We concluded that the tested entomopathogens and mycoparasites are compatible elements of integrated pest management.     

Production of cellulase by freely suspended and immobilized cells of Trichoderma reesei

Trichoderma reesei (QM 9123) was immobilized within the open porous network of reticulated polyurethane foam matrices, and the growth pattern, glucose consumption and cellulase production were compared with those of freely suspended cells. It was found that the method of immobilization was simple and had no detrimental effect on cell activity. Various production media, to be used after the cultivation of T. reesei were tried. It was found that a nitrogen source-free production medium gave the highest enzyme titers of 1.5 × 10³ FPA U l⁻¹. Similar results were obtained with both freely suspended and immobilized cells.     

水杉原生种群核心种质资源的繁殖特性

水杉(Metasequoia glyptostroboides)原生种群天然更新困难, 为探究其原因是否与繁殖特性有关, 本文以其核心种质资源(40株个体)为对象, 通过对生境、母树个体和种子性状的调查, 并结合田间播种试验, 分析其繁殖特性。以方差分析检测不同母树个体间种子性状、发芽率和幼苗生长特征的差异; 采用相关性分析和多元线性回归模型分析个体性状对其种子、发芽率及幼苗生长的影响; 通过Logistic模型拟合, 分析幼苗生长的节律参数。结果显示: (1) 40株母树个体仅有7株产种, 产种率仅为17.50%, 且不同母树个体间产种量差异显著(P < 0.05)。(2)不同母树个体间的种子千粒重、种子发芽率、幼苗存活率和基径生长量均存在显著差异(P < 0.05)。(3) 7株母树个体种子的平均发芽率为19.73%, 幼苗平均存活率为73.42%, 不同母树之间差异显著(P < 0.05)。(4)母树个体的胸径与种子千粒重、种子发芽率呈显著负相关(P < 0.05), 种子发芽率与幼苗存活率呈极显著正相关(P < 0.001), 树高与幼苗存活率呈显著正相关(P < 0.05)、与幼苗基径呈极显著正相关(P < 0.001)。(5)母树树高对幼苗存活率有显著正效应(P < 0.05), 胸径对种子发芽率有显著负效应(P < 0.05)。(6)苗高、基径的生长符合“S”型生长曲线(R ² ≥ 0.928)。水杉原生种群产种量低, 种子发芽率低、幼苗存活率较低, 且不同母树之间差异显著可能是造成其天然更新困难的原因。     

马尾松人工林林窗边缘效应对樟和红椿凋落叶难降解物质分解的影响

采用凋落物分解袋, 以四川低山丘陵区马尾松人工林人工砍伐形成的7个不同面积的林窗边缘(100、225、400、625、900、1225、1600 m²)为研究对象, 以林下为对照, 研究了2种乡土树种——樟和红椿凋落叶难降解物质(木质素、纤维素、总酚、缩合单宁)在不同大小林窗边缘的降解动态特征.结果表明:马尾松人工林林下与不同大小林窗边缘相比较,红椿凋落叶中除纤维素外,其余难降解物质的降解率以及樟凋落叶木质素降解率均显著高于林下.在全年分解过程中, 2种凋落叶4种难降解物质的降解率总体均呈现持续上升的趋势.其中,缩合单宁降解最快,其次是总酚和纤维素,而木质素降解最慢.随林窗面积的增大, 红椿凋落叶除纤维素外,其余难降解物质在中型林窗边缘(400、625 m²)具有相对较高的降解率,而樟凋落叶的木质素在625 m²林窗边缘时也表现出较高的降解率.在凋落叶分解过程中,难降解物质降解率与凋落叶袋内温度和凋落物质量均呈显著相关.中型林窗(400～625 m²)对凋落物分解过程中难降解物质的降解具有更显著的边缘效应, 而这种边缘效应与物种有一定关联.     

内蒙古天竺葵腐霉枯萎病病原菌

为了明确天竺葵腐霉枯萎病的病原菌种类,从内蒙古通辽采集天竺葵腐霉枯萎病样品,对病原物进行了分离、纯化和致病性测定,并对病原物进行形态学和rDNA-ITS序列分析鉴定。结果表明,从10个植物样品中分离得到16个腐霉菌株,分别属于终极腐霉Pythium ultimum var. ultimum、瓜果腐霉P. aphanidermatum和两个与P. ultimum var. ultimum相似的待定种。其中,P. ultimum var. ultimum的分离频率为75%、P. aphanidermatum的分离频率为12.5%,两个腐霉待定种的分离频率均为6.25%;P. ultimum var. ultimum是优势类群。致病性测定结果表明,4种腐霉菌都能引起天竺葵腐霉枯萎病,与自然发病症状相同,其中P. ultimum var. ultimum和P. aphanidermatum的致病性较强,发病率分别为71.4%和85.7%。     

Laboratory investigations on the potential of entomopathogenic fungi for biocontrol of Helicoverpa armigera (Lepidoptera: Noctuidae) larvae and pupae

The susceptibility of third instar Helicoverpa armigera to seven strains of three entomopathogenic fungal species, i.e. Metarhizium anisopliae, Beauveria bassiana and Paecilomyces fumosoroseus, was tested under laboratory conditions using the larval immersion method. High efficacies ranging from 68 to 100% corrected mortality were recorded with more profound effects in treatments with B. bassiana and P. fumosoroseus strains. The median lethal concentration (LC₅₀) for L3 was 6.0×10⁵ in M. anisopliae 79, 1.5×10⁵ in B. bassiana 124 and 4.2×10⁴ in P. fumosoroseus 14. These three strains were further used to characterize the age-dependent mortality of different larval stages (L2-L5) and the effect against pupae of H. armigera. Larval stages did not differ in their mortality but differed i in median lethal time, with shorter values recorded in the second instar. Tested fungi also caused a high reduction between 74.4 and 100% in the emergence of pupae using the soil inoculation method and the pupal immersion technique. All three fungal species, especially P. fumosoroseus, have a high potential for biocontrol of H. armigera larvae and also as a soil treatment targeting the pupae.