Contamination of barley seeds with Fusarium species and their toxins in Spain: an integrated approach

Fusarium is a globally distributed fungal genus that includes different species pathogenic to cereals among others crops. Some of these Fusarium species can also produce toxic compounds towards animals and humans. In this work, the presence of the most important Fusarium toxins was determined in barley seeds from Spain, sampled according to European Union requirements. The results obtained were compared with the presence of mycotoxigenic species considered responsible for their synthesis by using species-specific polymerase chain reaction protocols. Fumonisins B₁ and B₂, zearalenone, trichothecenes type A (T-2 and HT-2) and trichothecenes type B (deoxynivalenol and nivalenol) were analysed by using high-performance liquid chromatography. Deoxynivalenol and zearalenone were detected in 72% and 38% of the barley samples, respectively, at levels below European Union limits in all cases. However, the co-occurrence of both toxins in 34% of the samples suggested that synergistic activity of these two mycotoxins should be evaluated. Nivalenol and HT-2/T-2 were detected at low levels in 17% and 10% of the samples, respectively. Fumonisins occurred in 34% of the samples at levels up to 300?µg/kg. This suggested that they might represent a risk in Spanish barley, and to our knowledge, this is the first report on the presence of fumonisins in barley in this country. The species-specific polymerase chain reaction assays to detect mycotoxin-producing Fusarium species showed a very consistent correlation between F. verticillioides detection and fumonisin contamination as well as F. graminearum presence and zearalenone, deoxynivalenol and nivalenol contamination in barley samples. The approach used in this study provided information of mycotoxin contamination of barley together with the identification of the fungal species responsible for their production. Detection of the species with the current polymerase chain reaction assay strategy may be considered predictive of the potential mycotoxin risk in this matrix.     

对虾肠道中产毒镰孢菌抑制菌的筛选与鉴定

为了获得对产毒镰孢菌具有抑制效应的海洋细菌,从对虾肠道中分离细菌,并将分离得到的优势细菌与产T-2毒素的禾谷镰孢菌(Fusarium graminearum)(FG1207)进行固体对峙培养,具有抑菌圈的细菌菌落即为产毒镰孢菌的抑制菌。然后选取对FG1207具有抑制作用的细菌与FG1207进行液体共同培养,用LC-MS/MS技术检测菌悬液中T-2毒素含量,最后对具有抑制FG1207的生长和降解T-2毒素效果的细菌进行16s r RNA序列鉴定和VITEK2细菌生化鉴定。实验结果分离得到8株优势细菌,其中一株对FG1207的生长具有明显的抑制作用;LC-MS/MS检测发现该细菌与FG1207共同培养菌悬液中未检测到T-2毒素,说明该细菌不仅能够抑制产毒镰孢菌的生长,还能降解T-2毒素。经16s r RNA鉴定该细菌为海洋尼泊尔葡萄球菌(Nepal Staphylococcus Aureus),相似度为99.93%,VITEK2细菌生化鉴定的相似度为96.86%。     

禾谷镰刀菌对多菌灵抗性的监测及其演变规律

调查了江苏省1994-2007年小麦赤霉病的危害程度,监测了江苏省1985-2007年禾谷镰刀菌对多菌灵的田间抗性菌株频率,分析了禾谷镰刀菌对多菌灵的抗药性与小麦赤霉病发生程度及气象因子的相关.结果表明:小麦赤霉病在江苏省的苏南江浦等县中发生以上的年份占30.8%,而在江苏北部赣榆、高邮等县,小麦赤霉病中发生以上的年份占7.7%～15.4%.抗药性菌株频率的增减率与小麦赤霉病的发病程度、病情指数和小麦抽穗期4月中下旬的雨日呈极显著的相关关系.研究表明在农业生产上多菌灵防治小麦赤霉病仍然具有使用价值.     

丁香酚、香芹酚和百里香酚对禾谷镰刀菌的抑菌活性及机制

以转录组技术为基础,研究丁香酚、香芹酚和百里香酚对禾谷镰刀菌的抑制作用及作用机理。方法：借助体外抑菌实验测定丁香酚、香芹酚和百里香酚对禾谷镰刀菌菌丝生长、孢子萌发和呕吐毒素生物合成的有效作用浓度;通过测定丁香酚、香芹酚和百里香酚处理后菌丝液的电导率、ATP含量和丙二醛含量进一步从细胞水平探讨其作用位点;通过转录组学阐明丁香酚、香芹酚和百里香酚抑制禾谷镰刀菌生长和毒素合成的分子机制。结果：3 种植物精油活性成分中,百里香酚的抗真菌活性最强。丁香酚、香芹酚和百里香酚可破坏禾谷镰刀菌细胞膜完整性,引起电解质渗漏,能量代谢失衡。此外,3 种植物精油活性成分通过核糖体、线粒体结构和转录组水平上的酶合成发挥对禾谷镰刀菌的抑制作用。     

Impact of post-anthesis rainfall,fungicide and harvesting time on the concentration of deoxynivalenol and zearalenone in wheat

Field experiments were conducted to identify the impact of post-anthesis rainfall on the concentration of deoxynivalenol (DON) and zearalenone (ZON) in harvested wheat grain. Winter wheat plots were inoculated with Fusarium graminearum at stem extension (GS31) and prothioconazole was applied at mid-anthesis (GS65) to split plots and plots were subsequently mist irrigated for 5 days. Plots were either covered by polytunnels, irrigated by sprinklers or left as non-irrigated uncovered control plots after medium-milk (GS75). Plots were harvested either when ripe (GS92; early harvest) or three weeks later (late harvest). Fusarium head blight (FHB) was assessed each week from inoculation. At harvest, yield and grain quality was measured and grains were analysed for DON and ZON. Differences in rainfall resulted in contrasting disease pressure in the two experiments, with low FHB in the first experiment and high FHB in the second. Difference in FHB resulted in large differences in grain yield, quality and mycotoxin content. DON concentration was significantly (P < 0.05) higher in irrigated compared to covered and control plots in the first experiment, whereas in the second experiment, DON was significantly (P < 0.05) higher in the covered plots compared to the control and irrigated plots. ZON concentration was significantly (P < 0.05) higher in irrigated plots in both experiments. Later harvesting resulted in an approximate fivefold increase in ZON in the first experiment, but was not significantly different in the second experiment. Prothioconazole significantly (P < 0.05) reduced DON in both experiments, but gave inconsistent reductions to ZON. This is the first report to show that the post-anthesis rainfall can significantly increase ZON in wheat, which can increase further with a delayed harvest but may be significantly reduced with the application of prothioconazole. Importantly, in the absence of moisture late season, ZON remains at very low concentrations even when wheat is severely affected by FHB.     

玉米穗,茎腐病禾谷镰孢菌和串珠镰孢菌同工酶分析

对沈阳、河北、吉林、北京等地区玉米穗、茎腐病禾谷镰孢菌和串珠镰孢菌进行了可溶性蛋白和同工酶聚丙烯酰胺凝胶电泳,以研究玉米穗、茎腐病同种镰孢菌是否存在寄生专化性或生理分化现象。结果表明：各地区的玉米穗、茎腐病串珠镰孢菌同源性高,亲缘关系近,相似性系数在0．86～0．98之间,菌株间差异仅表现为个体间多样性。而两种病害禾谷镰孢菌亲缘关系困地区不同而有差异,河北、吉林两地区穗、茎腐禾谷镰孢菌间均具有很近的亲缘关系,相似性系数在0．93以上;但沈阳地区禾谷镰孢菌亲缘关系相对较远,相似性系数仅为0．65～0．67。     

室温下麦粒中脱氧雪腐镰刀菌烯醇(DON)及其隐蔽型(D3G)毒素累积分析

为了研究麦粒中脱氧雪腐镰刀菌烯醇（DON）及其隐蔽型脱氧雪腐镰刀菌烯醇-3-葡萄糖苷（D3G）的累积情况,将禾谷镰刀菌菌株F-1和5035分别人工接种至经高温灭菌、8 k Gy和15 k Gy辐照的麦粒中25℃培养7、14、21、28、35 d后,通过LC-MS/MS方法测定DON和D3G毒素在麦粒中的含量。不同处理的麦粒中DON含量均随培养时间延长逐渐增加;禾谷镰刀菌接种灭菌麦粒及15 k Gy辐照麦粒均未检出D3G毒素;禾谷镰刀菌接种8 k Gy辐照小麦籽粒后检测到隐蔽型毒素D3G,培养7 d时D3G最高且其含量随着培养时间延长逐渐降低;本文使用指数模型拟合25℃下F-1与5035接种麦粒（8 k Gy辐照）中D3G/DON的比值与时间关系的R2分别为0.97、0.93,R2均在0.9以上,说明指数模型能够较好地拟合本实验条件下时间与D3G/DON的比值的变化,为进一步后续研究提供依据。