Geographical distribution of Aspergillus flavus in peanut harvest period in China

In order to grasp the distribution of Aspergillus fiavus in the soil of peanut production areas in China, A. fiavus biomarkers were tested on 555 soil samples from 37 sampling points in 17 provinces, peanut fields in four agroecological zones(Southern area, Yangtze River Basin, Northern area, Northeast area). The results showed that(1) the cultivation amount of A. fiavus per gram of soil in the Yangtze River Basin is 1.30 times that of the southern area, 1.56 times that of the northern area, and...     

Effect of non-aflatoxigenic strains of Aspergillus flavus on aflatoxin contamination of pre-harvest peanuts in fields in China

Aflatoxin contamination of peanuts is one of the most concerns in peanut production in China. Applying non-aflatoxigenic Aspergillus flavus strains, based on competitive exclusion, has been proved to be a promising strategy to reduce aflatoxin contamination in pre-harvest peanuts. Two non-aflatoxigenic A. flavus strains collected in China, which have been proved effectively reducing aflatoxin in the laboratory, were mixed with high aflatoxin producer to the soil in peanut growing season. The two non-aflatoxigenic strains significantly (P ​< ​0.05) reduced aflatoxin contamination in peanut kernels under both normal and drought stresses in two fields. Compared to control, the total aflatoxin (sum of aflatoxin B₁ and B₂) was reduced 26.7–99.12% in field 1, and 84.96–99.33% in field 2. The aflatoxin was reduced 84.96–99.33% under drought stress in two fields. The present study indicated the non-aflatoxigenic A. flavus strains could be potential biocontrol agents for reducing aflatoxin contamination under field condition.     

油菜内生细菌多样性分析及菌株CanL-30生防潜力评估

为筛选防病促生的内生性细菌菌株,提高油菜的抗病性,对武汉地区甘蓝型冬油菜内生细菌进行了分离鉴定和多样性分析,同时对分离的内生细菌进行了拮抗菌株和促生菌株的筛选。结果表明：从采集到的油菜样本中共分离得到134株内生细菌,基于16S rDNA序列分析,发现这些菌株属于18个细菌属中的33个种,其中芽孢杆菌属、假单胞菌属和寡养单胞菌属占优势,分别占分离物总数的46.27%、15.67%和11.94%。油菜根、茎和叶内生细菌分离物的香农多样性指数分别为2.847、2.808和2.356,辛普森指数分别为0.956、0.939和0.907。经过平板筛选、离体叶片筛选以及活体油菜接种筛选,发现枯草芽孢杆菌（Bacillus subtilis）菌株CanL-30对灰葡萄孢（Botrytis cinerea）、立枯丝核菌（Rhizoctonia solani）和油菜黑胫病菌（Leptosphaeeria biglobosa）有拮抗作用,还具有稳定的抑制核盘菌的效果。进一步试验表明,菌株CanL-30主要通过产生抗真菌物质抑制核盘菌生长。研究还发现CanL-30能促进拟南芥和油菜生长。上述结果说明冬油菜存在丰富的内生细菌资源,从中可以筛选得到防病促生的细菌菌株。     

Bacillus subtilis SPB1 biosurfactant: Production optimization and insecticidal activity against the carob moth Ectomyelois ceratoniae

Bacillus subtilis SPB1 was shown to produce a lipopeptide biosurfactant. The insecticidal activity of this biosurfactant was evaluated against Ectomyelois ceratoniae Zeller, a moth pest of stored dates in Tunisia. The LC₅₀ and LC₉₀ values after six days of contact were 152 μg/g and 641 μg/g, respectively. To promote an economical production of this highly effective bioinsecticide, statistical experimental designs and response surface methodology were employed to optimize the concentrations of agro-industrial residues and humidity, for lipopeptide biosurfactant production by B. subtilis SPB1 under solid state fermentation. The optimal medium leading to a production yield near to 28 mg of crude lipopeptide preparation per g of wet solid material was composed of a mixture of 4.34 g of tuna fish flour and 5.66 g of potato waste flour with a moisture content of 76%.     

Effects of Bacillus subtilis strain QST 713 and storage temperatures on post-harvest disease development on greenhouse tomatoes

Tomato plants in two commercial greenhouses were treated with Rhapsody (Bacillus subtilis strain QST 713, rate of 1.45%) once every 4 weeks during 2012–2013 to determine effects on post-harvest fruit infection. Populations of Bacillus and disease incidence were monitored weekly from harvested fruit over an 18-week period. Population levels of Bacillus ranged from 75 to 110 × 10⁴ colony forming units (cfu) cm⁻² of fruit surface area one week after application to 25–30 × 10⁴ cfu cm⁻² of fruit surface area 4 weeks after application. Disease incidence on harvested fruit incubated at 21 °C for 7–10 days was variable, due to variation in inoculum levels within the greenhouse as well as variable environmental conditions. Both disease incidence and severity were significantly reduced on Rhapsody-treated fruit, especially in the 1–2 week period following application. Post-harvest storage temperature (13 °C vs. 21 °C) and incubation time (12 vs. 16 days) had a significant effect on final disease severity. Rhapsody-treated fruit incubated at 13 °C had an average of 1–2% fruit infection compared to up to 20% infection on untreated fruit at 21 °C. The most frequent pathogens affecting fruit quality were Penicillium sp. and Rhizopus stolonifer. Rhapsody applications made every 4 weeks maintained sufficiently high populations of Bacillus on the fruit surface to prevent spread of these fungi onto the fruit, resulting in significant post-harvest disease control on fresh market tomatoes. When combined with storage at 13 °C for no more than 12 days, disease was reduced to negligible levels.     

Strategies for administration of biosurfactant-producing pseudomonads for biocontrol in closed hydroponic systems

Zoospore-producing oomycetes are major plant pathogens of particular concern in hydroponic systems. Compared with pesticides, biocontrol using antagonistic microorganisms is a sustainable approach to control oomycetes. Previous research has demonstrated that biosurfactants and biosurfactant-producing microorganisms are potentially useful components of a sustainable biocontrol strategy.In this study three ways of supplying a biosurfactant-producing strain to a recirculating hydroponic cultivation system infected with a zoospore-producing plant pathogen were evaluated. The strain Pseudomonas koreensis 2.74 was added as washed cells, in its spent KB broth or in a minimal medium adapted from the nutrient solution, and compared with control treatments. A significant reduction in disease with up to 50% was achieved when a high concentration of washed cells was added weekly to the plant cultivation system. The disease suppression obtained through addition of washed cells equalled the effect achieved when the purified biosurfactant was used. Phytotoxicity was observed when the spent broth was included in the treatment.     

花生种子抗黄曲霉侵染性状遗传控制的研究

以高抗黄霉侵染亲本湛秋48和高感亲本粤油92及杂种后代F1，BC1，F2，F3为分析材料，研究了花生抗黄曲霉侵染的遗传控制，结果表明花生对黄曲霉侵染的抗性没有细胞质效应和胚乳效应，是由母株（2n）基因控制，表现为一对主基因和微效基因混合遗传模式。     

Improvement of Hanseniaspora uvarum biocontrol activity against gray mold by the addition of ammonium molybdate and the possible mechanisms involved

The efficacy of Hanseniaspora uvarum against gray mold by adding ammonium molybdate (NH₄–Mo) and the mode of actions were evaluated. The results showed that H. uvarum at 1 × 10⁶ CFU ml⁻¹ plus 1 mmol l⁻¹ NH₄–Mo greatly reduced gray mold in grape fruits. NH₄–Mo at concentrations of 1, 5, 10 and 15 mmol l⁻¹ significantly inhibited spore germination and mycelium growth of Botrytis cinerea. Population growth of H. uvarum was markedly inhibited by NH₄–Mo at 5 mmol l⁻¹in vitro and not affected by addition of NH₄–Mo at 1 and 5 mmol l⁻¹ in wounds combination of NH₄–Mo and H. uvarum induced higher activities of peroxidase (POD), polyphenoloxidase (PPO), phenylalanine ammonialyase (PAL), superoxide dismutase (SOD), catalase (CAT) and β-1,3-Glucanase than individual application of H. uvarum or NH₄–Mo. The enhancement of disease control may be directly because of the inhibitory effects of NH₄–Mo on spore germination and mycelial growth of B. cinerea in vitro, and indirectly because of the induced defense reactions by NH₄–Mo in grape berries.     

Production of monoclonal antibodies against AFLM (Ver-1), a middle key protein involved in aflatoxin biosynthesis

Aflatoxins are potent carcinogens, mutagens and teratogens, and are harmful to both humans and animals. As many as 30 genes are involved in aflatoxin biosynthesis. Among them, aflM (ver-1) gene was predicted to encode a 28-kDa NADPH-dependent ketoreductase (AFLM), which catalyzed middle enzymatic steps in aflatoxin biosynthetic pathway. AFLM (Ver-1) was proved to be necessary for conversion of versicolorin A (VERA) to demethylsterigmatocystin (DMST) in aflatoxin B₁ (AFB₁) biosynthesis. For these reasons, aflM gene was cloned and specific monoclonal antibodies for AFLM was developed to better define potential pathways of AFLM involved in AFB₁ biosynthesis. Monoclonal antibodies 11B2-1D7 and 3G5-4E7 were successfully screened out by immunizing mouse. Immunoblot analysis revealed that both had high sensitivity and specificity to identify native AFLM protein in A. flavus with detection limit of 11 ​ng/mL and 8 ​ng/mL respectively. These results showed that it was suitable for quantitative detection of AFLM in A. flavus isolate. Further investigation revealed that aflatoxin accumulations of various A. flavus were not dependent on AFLM biosynthesis. Overall, this is the first report for development for AFLM monoclonal antibody development and application in A. flavus quantitative detection.     

Suppression of rice sheath blight disease using a heat stable culture filtrate from Streptomyces philanthi RM-1-138

Streptomyces philanthi RM-1-138, isolated from the rhizosphere soil of chili pepper in southern Thailand, was investigated for its antagonistic activity against phytopathogenic fungi. In dual culture on glucose yeast-malt extract (GYM) agar plates, this strain suppressed the mycelial growth of all seven plant pathogenic fungi tested (Rhizoctonia solani PTRRC-9, Pyricularia grisea PTRRC-18, Colletotrichum gloeosporioides NBCRSR-3, Colletotrichum capcisi NBCRSR-15, Ganoderma boninense NBCRSR-26, Fusarium fujikuroi PTRRC-16 and Bipolaris oryzae PTRRC-36) with an 82.2–89.2% inhibition and that was most pronounced on R. solani PTRRC-9. Heat treatment of the culture filtrate from growing R. solani PTRRC-9 at 40 °C, 60 °C, 80 °C, and 100 °C for 30 min and 121 °C for 15 min had no negative effect on the inhibitory activity against R. solani PTRRC-9 tested on both solid and liquid culture. The effective dose (>80% inhibition) of culture filtrate in liquid culture was at 5.0% (v/v) while it was at 10% (v/v) on the solid medium. This effectiveness was similar to those of the four chemical fungicides tested. The effect of S. philanthi RM-1-138 against R. solani PTRRC-9 was investigated using SEM and TEM. The compounds produced by S. philanthi RM-1-138 induced alterations to the cell-wall structure of R. solani PTRRC-9, that resulted in the loss of cytoplasm materials by partial lysis. The greenhouse experiment revealed that using either the culture filtrate or the autoclaved culture filtrate from S. philanthi RM-1-138 effectively suppressed rice sheath blight disease by up to 65.6 and 60.8%, respectively.     

Trichoderma asperellum is effective for biocontrol of Verticillium wilt in olive caused by the defoliating pathotype of Verticillium dahliae

Verticillium wilt caused by a highly virulent, defoliating (D) pathotype of Verticillium dahliae is threatening olive production in Spain and other Mediterranean countries. This disease must be managed by an integrated strategy, in which biocontrol agents can play an important role. We have investigated the potential of Trichoderma asperellum strains for antagonism against V. dahliae and suppression of Verticillium wilt of olive caused by the D pathotype. First, we tested the antagonistic potential of T. asperellum strains Bt2, Bt3 and T25 against six V. dahliae isolates, four of the D and two of the nondefoliating (ND) pathotypes, in different in vitro assays. All T. asperellum strains overgrew the colonies of all V. dahliae isolates to a similar extent. However, extracellular compounds from strains Bt3 and T25 showed higher anti-V. dahliae activities than those of Bt2 in membrane assays. Also, growth of Bt2 was reduced by ND V. dahliae whereas that of Bt3 and T25 was not affected by V. dahliae-secreted compounds. In planta assays using strains Bt3 and T25, and ’Picual’ olive plants, showed that the two T. asperellum strains significantly reduced the severity of symptoms and the standardized area under the disease progress curve caused by highly virulent D V. dahliae, but not the final disease incidence. Strain T25 significantly increased growth of ‘Picual’ plants and displayed higher ability for colonizing the olive rhizosphere and establishing endophytic infection in olive roots than Bt3.     

新型复合型生物种衣剂SN102田间防效研究

为了安全有效地解决大豆苗期根部多种病害复合侵染的问题,利用微生物多样性及诱导抗病性理论,在辽宁省沈阳康平基地与黑龙江大庆基地,对新研发的一种兼抗大豆胞囊线虫与根腐病的新型复合型生物种衣剂SN102进行了为期2年的田间防治效果验证试验。生物种衣剂SN102是由本实验室自主研发,由巨大芽孢杆菌(Bacillus megaterium)Sneb482、简单芽孢杆菌(Bacillus simplex)Sneb545、费氏中华根瘤菌(Sinorhizobium fredii)Sneb183和产黄青霉菌(Penicillium chrysogenum)Snef805 4株生防菌株作为有效活性物质组合混配制成。结果表明:SN102对大豆幼苗生长有一定的促进作用,两年的平均胞囊抑制率分别为37.80%(康平)和28.95%(大庆),对大豆幼苗根腐病的平均防效分别为16.31%(康平)和29.57%(大庆),同时对大豆的平均增产率分别达到21.10%(康平)和12.36%(大庆)。SN102在不同地域的防病增产效果较稳定,具有很高的实际应用价值和开发潜力。     

Use of formulated Trichoderma sp. Tri-1 in combination with reduced rates of chemical pesticide for control of Sclerotinia sclerotiorium on oilseed rape

Sustainable strategies for control of Sclerotinia sclerotiorum on oilseed rape are needed. Here we tested combinations of Trichoderma sp. Tri-1, formulated with oilseed rape seedcake and straw, with reduced application rates of the recommended chemical pesticide carbendazim for control of this pathogen on oilseed rape. The treatment containing the recommended rate of carbendazim provided the greatest reduction in disease when compared with treatments containing individual applications of lower rates of this pesticide or the formulated Tri-1 treatment in all field experiments. Treatments containing formulated Tri-1 combined with carbendazim applied at 50% or 75% the recommended rate reduced incidence of disease to levels statistically similar to the treatment containing carbendazim applied at the recommended rate in two field experiments conducted at the Wuxue County field site where a rice-oilseed rape rotation was used. The treatment containing formulated Tri-1 combined with carbendazim applied at 75% the recommended rate reduced incidence of disease to levels statistically similar to the treatment containing carbendazim applied at the recommended rate in two field experiments conducted at the Wuhan field site where a soybean-oilseed rape rotation was used. Experiments reported here using two oilseed rape production rotations indicate that integration of a biologically based control tactic, such as formulated Tri-1, into a disease management strategy can increase oilseed rape production sustainability through reduction in the use of chemical pesticides.     

Enhancement of biocontrol efficacy of Pichia membranaefaciens by hot water treatment in postharvest diseases of citrus fruit

Effects of hot water treatment (HWT; 53 °C for 2 min) and Pichia membranaefaciens, either alone or in combination, on controlling Penicillium italicum, Penicillium digitatum, and natural infection in citrus fruit were investigated. Results showed that the combined treatment significantly reduced disease incidence and lesion diameters of blue and green molds in artificially inoculated fruit whether the pathogens were inoculated after or before the treatment compared with the treatment of P. membranaefaciens or HWT alone. The combination of P. membranaefaciens with HWT was as effective as the fungicide treatment in natural infection trials. Application of HWT did not affect the growth of P. membranaefaciens in the wounds of citrus fruit at 20 °C or 4 °C. P. membranaefaciens combined with HWT effectively enhanced the phenylalanine ammonia-lyase, peroxidase, polyphenoloxidase, chitinase, and β-1,3-glucanase activities and stimulated the synthesis of phenolic compounds. These results suggest that the use of HWT is a useful approach to improve the efficacy of P. membranaefaciens in postharvest diseases of citrus fruit.     

Combined use of Streptomyces sp. A6 and chemical fungicides against fusarium wilt of Cajanus cajan may reduce the dosage of fungicides required in the field

Biological control agents offer one of the best alternatives to reduce the use of pesticides. This investigation studied the tolerance to fungicides and integrated use of the potential biocontrol agent Streptomyces sp. A6 for control of Fusarium wilt of pigeon pea, Cajanus cajan. Streptomyces sp. A6 exhibited strong tolerance towards most of the fungicides used in the study at concentrations higher than those recommended for field applications. The isolate showed enhanced growth and mycolytic enzyme production in the presence of sulphur, mancozeb, carbendazim, fosetyl aluminium and triadimefon. The fungicides mancozeb, sulphur and carbendazim were selected for further studies. Effective concentrations (EC₅₀ values) of the test fungicides that reduced Fusarium spore germination and fungal biomass by 50% were determined. Similarly, the EC₅₀ for inhibiting fungal spore germination and reducing fungal biomass to 50% by Streptomyces sp. A6 and culture filtrate (CF) were also determined. Combining the EC₅₀ dose of the culture and CF with test fungicides was found to be more effective for controlling Fusarium infection in C. cajan compared to the sum of the effects of the individual treatments. Such combined use of biocontrol agent with fungicides can reduce the dosage of toxic fungicides in agricultural fields, thereby reducing environmental risks. Tolerance and synergistic interaction of Streptomyces sp. A6 with frequently used fungicides suggested its potential in integrated pest management. To the best our knowledge, this is the first extensive study on integrated use of Streptomyces species with fungicides.