柑桔黑斑病的发病特点及检测方法研究进展

柑桔黑斑病(Citrus Black Spot,CBS)是一种真菌性病害,主要为害果实,并产生褐色斑点,严重时蔓延至全果,造成果实腐烂,显著影响果实的品质和外观,降低经济价值,被欧美等国列为重要的检疫性病害,近年来该病在我国一些柑桔产区已上升为主要病害。本文主要从柑桔黑斑病的病原菌、发病特点及检测方法等几个方面进行简要的概述。     

重庆万州柑橘轮斑病菌的鉴定及防治药剂筛选

【目的】明确2018年起在重庆万州柑橘种植区新发生病害的病原菌,筛选有效防控药剂,为田间防治该病害和后续深入研究提供理论参考。【方法】通过组织分离法从患病样品中获得菌株,进行病原菌形态学、分子生物学和致病性鉴定,采用生长速率法测定不同药剂对目标菌株的毒力。【结果】此病害的病原菌为柑橘轮斑病菌Pseudofabraea citricarpa。病原菌对万州地区主栽的8个品种柑橘的叶、枝、果和昭通苹果及砀山酥梨果实具有致病性。苯醚甲环唑、咪酰胺、甲基硫菌灵等17种杀菌剂的EC50值小于3 mg/kg,代森锰锌与啶酰菌胺1：64比列复配、克菌丹与苯醚甲环唑1：1比例复配、代森锰锌和矿物油1:50比例复配对菌株生长抑制效果良好。【结论】重庆万州柑橘种植园区发生柑橘轮斑病,病原菌对柑橘枝、叶、果和其它果树果实都具有致病性。17种药剂单用或复配对病原菌生长有抑制作用,可进一步用于田间实验。     

Effect of defoliation by livestock on stem canker caused by Leptosphaeria maculans in Brassica napus

Brassica napus (canola, oilseed rape), an important break crop for cereals across the Australian wheat belt, is being rapidly adopted as a dual‐purpose (forage and grain) crop in mixed farming systems. Stem canker caused by the fungus Leptosphaeria maculans is the most important disease of B. napus in Australia. The primary source of inoculum is airborne ascospores released during autumn/winter which coincides with the grazing of dual‐purpose crops. Field experiments were defoliated by sheep to determine the effect of grazing on blackleg stem canker severity at plant maturity in B. napus cultivars differing in their resistance level and grazed at different times. One cultivar was sown on different dates to investigate the impact of grazing at the same time, but at different growth stages. Defoliation by mowing was compared to defoliation by livestock. Similar amounts of dry matter remained after defoliation by machinery (0·66 t ha^?1) or livestock (0·52 t ha^?1). However, stem canker severity was higher in the grazed (40% of crown cross‐section diseased) compared with the mown (25%) treatment, which was higher than the ungrazed control (9%). Stem canker severity generally increased with grazing, but the increase was eliminated or reduced in cultivars with good resistance. Grazing during vegetative plant growth minimized the increase in stem canker severity compared with grazing during reproductive growth. Currently, cultivars with good L. maculans resistance are recommended in high disease situations. To avoid excessive yield loss in dual‐purpose B. napus crops due to L. maculans it is recommended that such cultivars are grown even in low‐moderate disease situations.     

杜松赤枯病病原菌的研究

阐述了杜松赤枯病病原菌的研究结果 ,研究表明交链孢 (Alternariasp )和茎点霉 (Phomasp )是杜松赤枯病的主要致病真菌 ;两种病原菌均喜偏酸性的条件 ,菌丝生长发育的适宜pH值是 5～ 7;菌丝生长的适宜温度是 2 0～ 30℃ ,孢子萌发的适宜温度是 15～ 2 5℃ ,2 0℃时萌发率最高 ;Al ternariasp 在相对湿度 90 %以上能较好萌发 ,Phomasp 在湿度 10 0 %时才能萌发 ,在水滴中萌发率最高 ;两种病原菌对云杉和丹东桧的嫩枝叶也有较强的致病性     

草茎点霉粗毒素的产生条件及活性测定

为了寻求能够充分发挥草茎点霉粗毒素活性的最佳培养条件,笔者利用有机溶剂萃取草茎点霉发酵液,获得粗毒素,采用针刺法、种子萌发法确定草茎点霉毒素合适的提取条件及对鸭跖草的致病性。结果表明：草茎点霉胞外毒素活性较高,3种有机溶剂中乙酸乙酯萃取效果最好,产毒的最佳条件为：培养温度32℃、培养时间14天、培养方式为150 r/min震荡培养。粗毒素浓度在1000 μg/mL时种子萌发抑制率为26.09%,病斑面积达到6.85 mm2。萃取毒素采用有机溶剂的种类以及培养温度、培养时间、培养方式对草茎点霉粗毒素的活性影响很大。     

Mineralization of hydroxylated isoproturon metabolites produced by fungi

When exposed to the herbicide isoproturon, some soil fungi in pure culture metabolize the substance to hydroxylated metabolites. Hydroxylated metabolites of isoproturon have also been detected in soil studies. In an agricultural soil not previously exposed to isoproturon we found that the hydroxylated isoproturon metabolite N-(4-(2-hydroxy-1-methylethyl)phenyl)-N′,N′-dimethylurea mineralized faster than both isoproturon and its N-demethylated metabolite N-(4-isopropylphenyl)-N′-methylurea (MDIPU), thus indicating that mineralization of isoproturon is stimulated by fungal hydroxylation in this soil. In soils previously treated with isoproturon, in contrast, isoproturon and both its hydroxylated and demethylated metabolites mineralized at almost the same rate with up to 52% of the ¹⁴C-ring-carbon being degraded to ¹⁴CO₂ within 63 days. Thus hydroxylated metabolites of isoproturon do not seem to be more persistent than isoproturon, and hence may degrade before they can leach from topsoil and contaminate the aquatic environment. While an isoproturon-mineralizing bacterium Sphingomonas sp. SRS2 and a MDIPU-mineralizing mixed bacterial culture were able to deplete the medium of hydroxylated metabolites, little or no mineralization took place. This indicates that other bacteria must be present in the soil that are able to benefit from isoproturon being made available to mineralization by fungal hydroxylation.     

陕北榆树大量死亡原因探析

根据分离培养和接种试验结果，认为白榆死亡是由白榆干枯病感染流行造成，病原菌为茎点霉菌。其发展蔓延具有明显的流域特征：河谷台地、沟坝地、山坡基部发病较重；山顶、梁峁地和山坡中、上部发病轻。红足壮异蝽的危害能加重病害的流行和扩展。     

抗Cd菌株的筛选及其对Cd的去除特性

从高Cd含量的闪锌矿土样中进行了抗Cd并富集Cd菌株的筛选,并对高效菌株的吸附和去除Cd特性作了分析。结果得到一株对Cd具有很强抗性和富集能力的茎点霉菌F2,该菌可在2000mg·L-1的Cd浓度下存活,在液体培养下对培养基中Cd尤其是高浓度Cd具有较好的去除作用,菌体Cd含量可达28%。F2干菌体对重蒸水中Cd的吸附动力学研究表明,吸附过程符合一级吸附动力学方程,同时计算了动力学参数。冷冻干燥菌体对Cd的吸附能力远大于烘干菌体,并在较大Cd浓度范围和pH值范围内对Cd具有较好的去除效果。     

Influence of seed tuber infestation,chemical seed treatment,and pre-harvest climate on incidence of gangrene and dry rot of potato (Solanum tuberosum L.)

Summary In each of the five years 1978 to 1982, seed lots of cv. Bintje, variously infested byPhoma foveata Foister andFusarium solani var.coeruleum (Sacc.) Booth, as found by wound and cut tests, respectively, were planted in a series of field experiments at six sites in Sweden. A statistically significant relationship between seed and progeny infestation was found forP. foveata each year, and in three years forF. solani. Benomyl and thiabendazole mist treatments of seed tubers at grading in spring controlled the development of gangrene and dry rot in treated seed tubers, but did not consistently reduce the levels ofP. foveata andF. solani infestation in progeny from treated seed tubers. The site of cultivation markedly influenced mean levels ofP. foveata infestation, which were found to be related to temperature and rainfall during a 40 day pre-harvest period at the trail sites; however, mean levels ofF. solani infestation were not so related.