Restriction of potato and tomato late blight development by sub‐phytotoxic concentrations of boron

Boron is a microelement required for normal growth and development of plants but its positive effect is restricted to a narrow range of concentrations. The gradual increase in use of recycled water, which contains high concentrations of boron for irrigation, has already raised the level of boron in soils and plants in southern Israel. This research was conducted to examine the direct effects of sub‐phytotoxic boron concentrations on potato late blight epidemics and to explore the mode of action of boron against Phytophthora infestans. When boron was applied alone to field grown potato plants it did not affect the epidemic. However, together with a reduced rate of the fungicide Melody Duo (propineb + iprovalicarb), boron improved late blight suppression compared to plants treated with the fungicide alone. The ED₅₀ of boron against P. infestans (256·4 mg L^?1) was about 6400 times higher than the ED₅₀ value of the fungicide chlorothalonil (0·04 mg L^?1), indicating that boron does not have a direct fungicidal activity that would explain the level of protection seen in the field. In greenhouse experiments conducted with potted tomato plants, boron decreased late blight severity in both treated leaves and distant leaves not treated with boron. The results suggest that boron is active locally but also may induce systemic acquired resistance against P. infestans.     

缬霉威原药毛细管气相色谱分析方法研究

本文采用毛细管气相色谱法,以邻苯二甲酸二环己酯为内标,用HP-5毛细管柱和氢火焰离子化检测器,对缬霉威原药进行分离和定量分析.结果表明,该分析方法的线性相关系数为0.999 8,标准偏差为0.37,变异系数为0.38％,平均回收率为100.08％.     

三种羧酸酰胺类杀菌剂对黄瓜疫霉菌不同发育阶段的影响及其敏感性测定

离体条件下测定了3种羧酸酰胺类(Carboxylic acid amides,CAAs)杀菌剂氟吗啉、烯酰吗啉和异丙菌胺对黄瓜疫霉菌不同生长发育阶段的抑制作用。结果表明,3种杀菌剂抑制黄瓜疫霉菌休止孢萌发的EC50值分别为0.54,0.46和 0.34 μg/mL;抑制菌丝生长的EC50值分别为0.92,0.70和0.67 μg/mL;抑制孢子囊形成的EC50值分别为0.48,0.31和0.26 μg/mL。但对游动孢子的释放、游动及休止孢的形成均没有抑制作用。氟吗啉、烯酰吗啉和异丙菌胺抑制田间采集的供试菌株菌丝生长的平均EC50值分别为1.09(±0.24),0.29(±0.04)和0.32 (±0.07) μg/mL,供试菌株对3种杀菌剂的敏感性均呈正态分布,未检测到抗药性菌株的存在。     

葡萄霜霉菌对仿生杀菌剂缬霉威的敏感基线及其抗性突变体生物学性状的研究

 本文对葡萄霜霉菌对缬霉威的抗性风险评估进行了研究。采集尚未使用过缬霉威的105个葡萄霜霉菌株,建立其对缬霉威的敏感基线。葡萄霜霉菌对缬霉威的有效抑制中浓度EC₅₀为0.04～0.60 μg·mL^-1,其敏感性频率符合正态分布,表明这105株葡萄霜霉菌对缬霉威均表现敏感。取其中10株敏感菌的孢子囊经紫外线(UV)诱导,获得4个缬霉威抗性突变体,突变频率为6.8×10^-7。将这10株葡萄霜霉菌孢子囊在叶片上进行缬霉威药剂驯化处理获得7个抗性突变体。11个抗性突变体的EC₅₀值为4.37～14.11 μg·mL^-1,抗性水平17.4～71.6。在未用药处理的健康葡萄叶片上继代培养10代后,这11个抗性突变体抗性水平保持在17.1～71.0。其中药剂驯化获得的7个抗性突变体和1个紫外诱导获得的抗性突变体的抗性水平均表现稳定遗传。但是,其余3个紫外诱导获得的抗性突变体抗性水平明显下降。与各亲本菌株进行比较,11个抗性突变体的潜育期、侵染率、病斑扩展速度和产孢能力都有显著不同。其中2个药剂驯化获得的抗性突变体和3个紫外诱导获得的抗性突变体表现潜育期变长,2个药剂驯化抗性突变体和1个紫外诱导抗性突变体表现侵染率下降。表明在一些情况下,葡萄霜霉菌抗性突变体的潜伏期和侵染率会发生改变。药剂驯化获得的抗性突变体产孢能力存在显著差异,但与抗性突变与否无关。缬霉威与嘧菌酯、甲霜灵、烯酰吗啉和霜脲氰之间无交互抗药性。推测:葡萄霜霉菌对缬霉威为中到高等抗性风险,今后应定期对葡萄霜霉菌对缬霉威的抗性发生动态进行监测。