Effects of plant age on disease development and virulence of Clavibacter michiganensis subsp. michiganensis on tomato

The effect of plant age at the time of inoculation on the severity of bacterial wilt and canker disease caused by Clavibacter michiganensis subsp. michiganensis (Cmm) was examined in six greenhouse experiments. The period during which inoculations led to wilt and death of tomato plants was defined. This period, designated ‘window of vulnerability’, ranged from transplanting to the 17‐ to 18‐leaf stage. Plants inoculated after this period expressed disease symptoms but did not wilt or die. No significant changes in disease incidence were observed when leaves of different ages were inoculated. Yield accumulation was significantly reduced in plants inoculated within the window of vulnerability compared with those inoculated after this period. Expression of virulence genes, viz. celA, encoding a secreted cellulase, and the serine protease‐encoding pat‐1, chpC and ppaA, was induced during the early stages after inoculation in plants inoculated within the window of vulnerability. Differences in Cmm population between plants inoculated within and outside of this period were insignificant after the first week post‐inoculation, indicating that differences in disease severity, yield loss and expression of virulence determinants are not correlated with Cmm population level. Results suggest that implementation of precautionary measures during the window of vulnerability to avoid secondary spread of Cmm will have a season‐long effect on plant mortality and may minimize, or even prevent, yield losses.     

M13分子标记快速区分树木溃疡病原真菌的种类

树木溃疡病菌具有寄主多样性、危害症状复杂且分布广泛的特点,快速简便地区分真菌类别是杨树溃疡病研究及防治中需要解决的重要问题。在对树木溃疡病菌的遗传多样性研究,发现以M13为引物的PCR扩增可以在不同的种类之间产生稳定分化的带型。因此,本研究分离了43株18种树木溃疡病相关真菌,并且对这些菌株进行rDNA-ITS序列测定及M13-PCR。结果显示,M13带型差异与真菌的特定种类相对应。因此,认为M13分子标记可以准确快速地鉴定、区分树木溃疡病菌。     

福美砷与抗寒剂混配喷雾防治苹果树腐烂病研究

采用Dn-311近似饱和最优设计三因素五水平试验，研究了福美砷与抗寒剂分别以不同浓度混配及不同时期喷雾对苹果树腐烂病的防治效果。研究表明，福美砷与抗寒剂混配后的喷雾时期是影响防效的主要因子，喷雾时期不同防病效果差异显著。4月中旬及11月中旬两个喷雾时期对提高防效至关重要。两因子交互效应防效≥80％的最佳区域均分布在各因子编码值的－2～－1.414及1．414～2之间。福美砷与抗寒剂混配使用的优化农艺措施为：在青海省乐都地区，喷雾期应选在4月中旬和11月中旬；福美砷浓度用50－75倍，抗寒剂浓度取100－150倍为宜。     

Bacterial canker of olives caused by of Pseudomonas syringae pv. syringae in Iran

Guilan is one of the main province olive oil producers in Iran. The culture of olive trees is of considerable importance. One problem that affects Iran olive orchards is a disease bacterial canker caused by Pseudomonas syringae pv. syringae. In this research, the bacterium was recovered from sunken brown stem lesions on 2-year-old olive trees cv. Marie, during survey from olive orchards in different areas of Guilan province. Samples were taken from infected tissues and were washed with sterile distilled water and crushed in peptone water. Then 50 μl of the extract was cultured on NA and King's B medium containing cyclohexamid antibiotic (50 μg/ml). After 48–72 h, bacterial colonies were selected. Based on morphological, physiological, biochemical, pathogenicity properties and PCR methods with specific primers the predominant pathogenic type was identified as P. s. pv. syringae. This is the first report of the existence of P. s. pv. syringae on olive trees in Iran.     

樟树溃疡病原菌生物学特性及室内毒力测定

为明确福建省樟树溃疡病病菌JY-5(Neofusicoccum parvum)的生物学特性,筛选有效的化学杀菌剂,测定了病原菌的生物学特性,并进行了12种化学杀菌剂对病原菌的毒力以及室内盆栽药效试验。研究结果表明,JY-5菌株在PDA培养基上生长最旺盛,孢子萌发率最高,其次是PSA,且两者之间无显著性差异。最适碳源为葡萄糖,最适氮源为蛋白胨和牛肉浸膏,最适pH值为6~8,最适温度为30℃,致死温度为50℃,最适光照条件为全光照培养。分生孢子萌发需要高湿度条件,在水滴中6 h萌发率达到89.33%。毒力测定结果显示,菌落抑制效果最好的为精甲·咯菌腈(EC90=0.129 mg·L^-1),其次是戊唑醇(EC90=0.151 mg·L^-1)、氟硅唑(EC90=0.176 mg·L^-1),效果最差的药剂为啶酰菌胺(EC90=55309.942 mg·L^-1)。盆栽药效试验结果显示,相同的药剂预防作用明显大于治疗作用,且随着药剂浓度的提高而增加。精甲·咯菌腈(400 mg·L^-1)的保护和治疗效果为最佳,抑制率分别为92.44%和87.50%。     

杨树冰核细菌溃疡病损失估测及防治指标

在东北杨树冰核细菌溃疡病重发区和发生区,分别不同树种,林龄和立地条件,选设具有代表性的样地,采用野外均匀分布,典型整群抽样调查和树干解析的方法,获得１２０块样地,２７０株解析木的调查数据,确定了病情指数与材积损失率相关数律,建立了东北地区杨树冰核菌溃疡病材积损失估测的模型,并以此推算出了东北地区相应的经济危害允许水平模型和防治指标的计算模型。     

陕西苹果树腐烂病病原菌的鉴定

分别从陕西各县区采样分离鉴定表明:引起陕西苹果腐烂病的病原菌主要为苹果壳囊孢属(Cytospo-rasp.),其次是梨壳囊孢属(C.carphospermaFr.)。回接及致病性测定表明:两种病原菌分别单独和混合接种后的致病率分别为100%,87%,100%。     

Cut-off shoots method for estimation of partial resistance in apple cultivars to fruit tree canker caused by Neonectria ditissima

Fruit tree canker, caused by the fungus Neonectria ditissima, is an economically devastating disease in apple orchards, especially in north-western Europe. Complete resistance has not yet been reported in apple, but variation in levels of partial resistance has been described and could be valuable in plant breeding programmes. A screening method based on spore inoculation of manually inflicted leaf scars on cut shoots was evaluated for reliability and repeatability in discrimination of 11 apple cultivars during two years – 2012 and 2013 – in two different facilities – biotron and standard greenhouse – and different time periods (February–May). The resulting cankers were counted (infection percentage), first appearance noted (incubation period) and lesion size measured at regular intervals during a period of 25–29 days for comparison of resistance levels. Results of two-way analysis of variance and correlation analyses showed that the area under the disease progress curve yielded the most robust data. This parameter was then applied for screening 30 apple cultivars using the same cut-shoot method. ‘Elise’ showed very high susceptibility, while the ornamental ‘Prairifire’ showed the highest level of partial resistance. Results suggested that cut shoots can be used to assess levels of resistance among cultivars, but great care must be taken to provide stable experimental conditions.     

Treponemes-Infected Canker in a Japanese Racehorse: Efficacy of Maggot Debridement Therapy

A 3-year-old thoroughbred colt presented with canker on its left hind foot. Subsequent development of cottage cheese-like horns and dermatitis disturbed healing, despite the use of miscellaneous orthodox treatment approaches to the lesions. Histological examination revealed exudative and suppurative dermatitis, and proliferatively suppurative epidermitis infected with helically coiled treponemes. Total debridement under general anesthesia led to a temporary improvement, but the ground surface regenerated abnormal epidermis similar to that observed initially after surgery. Maggot debridement therapy (MDT) was attempted, which removed all the abnormal tissue. After MDT, general farriery trimming helped to correct the distorted ground surface, and the horse returned to constant training and eventually raced. This case shows that MDT was successfully used for treatment of an intractable and treponemes-infected canker.