Research Progress in Biological Control of Soft Rot of Amorphophallus konjac

In this paper,the main control methods of soft rot of Amorphophallus konjac are reviewed,with a focus on the current research status of using plant growth promoting rhizobacteria for biological control of soft rot of A.konjac,and future research directions are looked forward to.

Screening of Antagonistic Actinomyces against Soft Rot of Amorphophallus konjac and Its Antibacterial Activity

[Objective] Antagonistic actinomyces of Amorphophallus konjac soft rot were isolated from the soil,the antibacterial activity of the fermentation was detected,and its active components were separated.[Method] The antagonistic actinomycetes were screened using plate confrontation culture method.The SJK18 antagonistic strain with strong activity was conducted single-factor tests using different carbon sources,nitrogen sources,temperatures and pH value as the culture condition,and the antibacterial activities of fermentation liquid was determined,respectively.The fermentation liquid of antagonistic strain was extracted with alcohol and acetic ester,and their antibacterial activities were determined.[Result] A total of 112 strains of actinomycetes were obtained,and 11 strains had antibacterial activity.The antibacterial activity of SJK18 strain was the strongest in the single-factor test,when the corn powder was adopted as the carbon sources,KNO3 was the nitrogen source,the temperature was 30 ℃ and the pH was 6.0,the appropriate pH value for the activity was 5.5-10.0.The diameters of inhibition zone of alcohol extract and raffinate of ethyl acetate were 17.0 and 20.0 mm,respectively,while the extraction of ethyl acetate had no antibacterial activity.[Conclusion] A strain of actinomyces with strong antibacterial activity against soft rot of A.konjac was obtained.

Effects of Nitrogen, Phosphate and Potassium Fertilizers on Soft Rot of Konjac Based on Grey Correlation Analysis

[Objective] The effects of different application amounts of nitrogen, phos-phate and potassium fertilizers on soft rot of konjac were investigated in this study. [Method] The grey correlation analysis was adopted to evaluate the correlation be-tween the application amount of nitrogen, phosphate and potassium fertilizers and the occurrence of soft rot of konjac. [Result] The excessive application of nitrogen fertilizer would induce the occurrence of soft rot of konjac, but the application of potassium fertilizer had a good control effect on soft rot. [Conclusion] The applica-tion amount of nitrogen fertilizer should be control ed reasonably in the planting of konjac, but the application amount of phosphate and potassium fertilizer could be in-creased to some extent, reducing the occurrence of soft rot of konjac.

Comparative Study on the Efficacies of 11 Chemical Agents against Taro Soft Rot Caused by Pectobacterium aroidearum

[Objective]The paper was to screen the effective agents for effectively controlling the occurrence and prevalence of taro soft rot.[Method]The fungicidal effects of 11 fungicides on taro soft rot were determined by inhibition zone method.[Result]0.3%Tetramycin,25%bromothalonil,3%Zhongshengmycin and 30%zinc thiazole had better antifungal effect on Pectobacterium aroidearum at recommended concentration.The indoor toxicity of four fungicides showed that the EC50 of 0.3%tetramycin AS was the smallest of 0.6μg/mL,indicating that tetramycin had the largest toxicity and the best inhibitory effect against P.aroidearum;followed by 25%bromothalonil EC and 3%Zhongshengmycin WP,with the EC_(50) of 2.57 and 97.72μg/mL,respectively;the inhibitory effect of 30%zinc thiazole SC against P.aroidearum was the poorest.[Conclusion]The study provides a reference for screening out new and efficient chemical agents against taro soft rot.

Field Efficiency Trial of 72% Streptomycin against Konjac Bacterial Soft Rot

72% Streptomycin soluble powder was used to control konjac bacterial soft rot in the study. The control efficiency and yield of different treatments were investigated,and the benefit was analyzed. The control scheme against konjac bacterial soft rot was as follows: spraying 72% atreptomycinon twice on rotation fields after all the seedlings were strong and uniform,or irrigating roots with 72% atreptomycinon once and spraying twice on continuous cropping fields.

Decay threshold of acetylated rattan (Calamus manan) against soft rot

We investigated the resistance of acetylated rattan against soft rot and other soil inhabiting micro-organisms in comparison with wood of beech and Scots pine. Calamus manan of 10 and 13 years old under rubber tree canopy was acetylated to different levels by reaction times （0.25 to 30 hours） and was tested for soft rot decay for 32 weeks. Acetylated rattan at decay protection thresholds of 15.4% and 16.2% weight gain （WG） were fully protected, as shown by both weight loss and strength loss criteria. The static bending properties of untreated rattan decayed by soft rot were significantly lower than for acetylated rattan.

Identification and Control of Radish Alternaria Leaf Spot, Black Rot, Soft Rot, Virus Disease and Hollowness

The damage characteristics and occurrence regularity of radish alternaria leaf spot, black rot, soft rot, virus disease and hollowness are introduced in the paper, and the corresponding control method is proposed from two aspects of agricultural control and chemical control.

Identiffcation of soft rot resistance loci in Brassica rapa with SNP markers

Soft rot caused by Pectobacterium carotovorum(Pc)is a devastating disease of Brassica rapa,causing substantial reductions in crop yield and quality.Identifying genes related to soft rot resistance is the key to solving this problem.To characterize soft rot resistance,we screened a soft rot-susceptible Chinese cabbage(A03),a resistant pakchoi(‘Huaguan’),and a resistant mutant(sr).An F_(2) population was generated by crossing susceptible Chinese cabbage A03and resistant pakchoi‘Huaguan’to identify quantitative trait loci(QTLs)that confer soft rot resistance.A high-density genetic map was constructed and the three QTLs identified contain 166 genes.Based on available transcriptome data,we analyzed the expression of the 166 genes during an important defense regulatory period in Pc infection in both A03and the resistant mutant sr.Among the 166 genes,six candidate genes were related to the soft rot defense response in B.rapa.TIFY10B(JAZ2,BraA07g038660.3C)was located in the major soft rot resistance QTL,DRQTL-3 on A07,and we speculate that this gene may play an important role in the defense mechanism against soft rot in B.rapa.This study lays the foundation for further investigations on the mechanism of soft rot resistance in B.rapa crops.

Genetic Relationships of Soft Rot Bacteria Isolated from Konjac in China by Amplified Fragment Length Polymorphism (AFLP) and 16S rDNA Gene Sequences

Twenty-three isolates of soft rot bacteria from konjac corms were examined for their diversity using 16S rDNAs and AFLP technology. Both methods clustered two groups, dependent on their biotype characterization of Pectobacterium carotovora subsp. carotovora (P.c.c) and Pectobacterium chrysanthemi (P.ch), respectively. Of all isolates, 17 (73.9%) belonged to P. ch, indicated as the main pathogenic bacteria of konjac producing areas in China. The genetic variation among isolates from the same biotype was also rich, not consistent with the distances of the geographic sources.

Characterization of the Causal Organism of Soft Rot of Tomatoes and Other Vegetables and Evaluation of Its Most Aggressive Isolates

To isolate the causal organism of soft rot of vegetables, diseased samples of potato, tomato, carrot, chilies, and bell pepper, were analyzed in the lab, using nutrient agar (NA) and/or the enrichment host (Bell pepper) technique. Successful isolations were purified by sub-culturing, identified as Erwinia carotovora subsp. carotovora through biochemical tests and their pathogenicity was confirmed through inoculation on green tomato fruits. The isolates were tested for their aggressiveness to find out the most aggressive one in term of producing maximum soft rot on tomatoes. CRD (completely randomized design), with four replication was used and data were analyzed using LSD (least significant test) test. Among the five isolates evaluated for aggressiveness on tomato fruits, chili isolate was found to be the most aggressive followed by tomato and potato isolates producing 22.3 mm, 7.9 mm, and 7.8 mm diameter soft rot lesions, respectively.

Detection and Identification of Potato Soft Rot <i>Pectobacterium carotovorum</i>Subspecies <i>carotovorum</i>by PCR Analysis of 16S rDNA in Jordan

Various bacterial species are known to be agents causing soft rot of potatoes. The results of this study showed that potato soft rot is widely spread in different potato planting areas in Jordan. A survey was conducted through the years 2013-2015 to detect potato soft rot disease in Jordan, two hundred and four rotted potato samples were collected from different potato growing areas through different potato growing seasons. One hundred and thirty one bacterial isolates were isolated, purified on selective media and identified as Pectobacterium carotovorum subspecies carotovorum (Pcc) by different biochemical and physiological tests. Furthermore, 131 Pcc Jordanian (Jo) isolates were identified by PCR analysis of total DNA extracted from isolates that were biochemically identified as Pcc using universal primer Fd1/Rd1. Cloning and sequencing of representative PCR products, amplifying the 16S rDNA region were done. Phylogenetic analysis of the Pcc Jo-isolates revealed other than 90% similarity with different reference Pcc strains available at the GenBank. Different rot causal agents also were detected by PCR amplification and further sequences. The sequencing data revealed similarities to Pseudomonas fluorescence, Enterobacteriaceae genera such as Enterobacter spp., Serratia spp. and Klebsiella spp., in addition to Pectobacterium carotovorum subsp. carotovorum. This study indicated that using molecular techniques such as amplification of 16S rDNA region is a sensitive and specific method for detecting Pcc as potato soft rot causal agent. So far this is the first study where Pcc has been identified by using PCR and sequencing approaches in Jordan.

Use of Polymerase Chain Reaction for Identification of the Pathogen and Management of Potato Soft Rot with Zinc Application

Effect of different Zinc doses was investigated against Erwinia carotovora ssp. atroseptica, the potato blackleg/soft rot causing organism, during 2009 and 2010 in Department of Plant Pathology and Institute of Biotechnology and Genetic Engineering, The University of Agriculture, Peshawar-Pakistan. Out of 200 tested samples, 21 of them were proved to be Eca. However, these tentative Eca isolates showed some characteristics which were unexpected for Eca. We, therefore, decided to perform Polymerase Chain Reaction using Eca-specific primers, Eca1F and Eca2R for confirm identification. For disease management, at the time of sowing, pots containing 5 kg sterilized soil were applied with Zinc in four different treatments i.e. 8 mg, 10 mg, 12 mg and 14 mg along with one control. Results indicated that 12 mg (4.8 kg Zn ha-1) were better doses in controlling the disease up to 73% and increasing the yield up to 117% as compared to control plants.

Bacteriophages Isolated in China for the Control of Pectobacterium carotovorum Causing Potato Soft Rot in Kenya

Soft rot is an economically significant disease in potato and one of the major threats to sustainable potato production.This study aimed at isolating lytic bacteriophages and evaluating methods for and the efficacy of applying phages to control potato soft rot caused by Pectobacterium carotovorum.Eleven bacteriophages isolated from soil and water samples collected in Wuhan,China,were used to infect P.carotovorum host strains isolated from potato tubers showing soft rot symptoms in Nakuru county,Kenya.The efficacy of the phages in controlling soft rot disease was evaluated by applying individual phage strains or a phage cocktail on potato slices and tubers at different time points before or after inoculation with a P.carotovorum strain.The phages could lyse 20 strains of P.carotovorum,but not Pseudomonas fluorescens control strains.Among the 11 phages,Pectobacterium phage Wc5r,interestingly showed cross-activity against Pectobacterium atrosepticum and two phage-resistant P.carotovorum strains.Potato slice assays showed that the phage concentration and timing of application are crucial factors for effective soft rot control.Phage cocktail applied at a concentration of 1×10^9 plaque-forming units per milliliter before or within an hour after bacterial inoculation on potato slices,resulted in>90%reduction of soft rot symptoms.This study provides a basis for the development and application of phages to reduce the impact of potato soft rot disease.

猕猴桃采后真菌病害生物防治研究进展

猕猴桃果实易受多种病原真菌的侵染,采后易发生软腐病、灰霉病、青霉病等严重危害果实品质的真菌性病害。传统的有效防治方法主要为采前使用化学杀菌剂,但其易污染环境并可能危害人类健康。目前,已有一系列生物防治方法被研究并报道,这些方法可有效防控猕猴桃采后真菌病害:第一类为天然抑菌物质,包括植物提取物和其他天然物质;第二类为拮抗微生物,包括生防酵母、生防细菌、生防木霉,生防菌也能与物理及化学方法协同发挥作用。本文概述了各类生物防治方法在猕猴桃采后真菌病害绿色防控方面的研究进展及生防机理,并提出了目前存在的问题,最后展望了这一领域今后的研究方向。

3株生防菌对猕猴桃软腐病的作用

为探究生防菌对猕猴桃软腐病的作用,选用前期获得的3株生防菌(贝莱斯芽孢杆菌P2-1、耐盐芽孢杆菌PL7和多黏芽孢杆菌NL4)进行室内抑菌试验、猕猴桃软腐病接种和自然发病防治试验,并研究了3株生防菌对猕猴桃果实病程相关基因表达的影响。试验结果表明,菌株P2-1、PL7和NL4对猕猴桃软腐病菌(Botryosphaeria dothidea)菌丝生长的抑制率分别为83.49%、74.82%和49.33%,P2-1的抑制效果最好,PL7次之,NL4最差;3株生防菌对接种猕猴桃软腐病均具有抑制作用,其中以P2-1的效果最好,PL7次之,NL4最差;3株生防菌均能显著降低猕猴桃软腐病自然发病率,其中以P2-1处理的发病率最低;3株生防菌处理均对猕猴桃果实品质无影响;3株生防菌处理猕猴桃果实后,果实中基因PR1、PR5和SOD的表达显著上调。研究结果可为菌株P2-1、PL7和NL4开发为防治猕猴桃软腐病的生物制剂提供参考。

不同菜心品种对软腐病的抗性鉴定

【目的】近年来,随着菜心栽培面积扩大和重茬现象的出现,菜心病害逐年加重,其中软腐病是危害菜心的主要病害之一,严重影响其产量和品质。通过接种软腐病病菌对菜心品种进行抗病性评价,以期筛选出抗病品种。【方法】采集具有典型软腐症状的菜心病样,通过组织分离、形态学和分子生物学方法进行鉴定,获得软腐病病菌。以52份不同菜心品种为试验材料,采用苗期喷雾接种法进行接种:用刀片在菜心茎部轻划2个约5mm刀口,使用小型手持喷雾器将1×108CFU/mL菌液喷到伤口表面,接种完成后3 d,测定病情指数和软腐病分级,评价52份菜心品种的软腐病抗性水平。【结果】经组织分离得到分离物,经柯赫氏法则验证菌落形态特征、16S rDNA序列分析表明,菌株为菜心软腐病致病菌,在NA培养基上形成的菌落呈圆形、半透明、乳白色、中心突起、边缘平滑,能使菜心的组织腐烂,接种于菜心苗后叶片呈湿腐萎蔫症状。52份材料中,大多数菜心品种对软腐病的抗性存在显著差异,其中,高感材料35份、感病材料16份,整体而言,高感或感病材料占98.1%;中抗材料1份(丰裕4号菜心);无高抗或免疫品种。上述结果表明,52份菜心品种中抗软腐病的材料较少,这可能是广东省菜心软腐病发病较严重的原因之一。【结论】52份菜心品种中,软腐病高感或感病材料占98.1%;中抗材料1份;无高抗或免疫品种,可为选育和推广抗软腐病的菜心品种提供科学依据。

生防菌ZF510的分离鉴定及其对白菜细菌性软腐病的防治效果研究

白菜软腐病是由巴西果胶杆菌Pectobacterium brasiliense引起的一种危害严重的细菌性病害。目前,针对蔬菜细菌性软腐病高效防治的产品较少。为了筛选对白菜细菌性软腐病具有良好拮抗效果的生防细菌,本研究从白菜根际土壤中分离到一株对细菌性软腐病菌具有显著拮抗效果的生防细菌ZF510。经过形态学特征观察、生理生化特征和多基因系统发育树分析,并通过盆栽试验验证拮抗菌株对白菜细菌性软腐病的防治效果。结果表明,菌株ZF510为东湖假单胞菌Pseudomonas donghuensis,在代谢过程中产生蛋白酶,有合成IAA能力、嗜铁能力、溶磷能力。通过抑菌谱分析,证明菌株ZF510对巴西果胶杆菌、野油菜黄单胞野油菜致病变种等7种病原细菌具有显著的拮抗效果。采用二分皿法测定其挥发性物质对立枯丝核菌、黄瓜蔓枯病菌、茄匍柄霉3种病原真菌均有抑制效果。盆栽试验结果显示,接种菌株ZF510的白菜细菌性软腐病症状明显减轻,防治效果达到44.56%。综上所述,菌株ZF510具有良好的生防潜力和应用前景。

Influence of Sanitization Process on Maintaining Sweet Potato Quality for Export

The whole cold-chain for exporting sweet potato(native variety“Abees”),to foreign market included immediate curing operation directly after harvest helped in healing skin texture,however,in order to reduce postharvest soft rot(Rhizopus stolonifer)incidence following trimming,and washing,ultraviolet light(UV-C)treatment was used as a main sanitizer for eliminating the soft rot.Exposure of the roots to UV-C(254 nm)was applied in a UV-C room on freshly harvested and cured sweet potato while rolling up on a movable line at 20 cm distance for 1,2,and 3 hr.As combining UV-C treatment with chlorine(200 ppm)on roots,marked and significant reduction of the total microbial load and Rhizopus potential was achieved on root surfaces respectively compared with chlorine alone.It also reduced soft rot percentage to almost 0%infection.After 3 months of cold-storage,quality assessment of sweet potato showed that root characteristics were markedly maintained.The ability of UV-C light to induce phenylalanine ammonia lyase(PAL)enzyme activity in root tissue and maintain the activities of peroxidase and polyphenol oxidase,however with slight increase,was detected.UV-C caused an increase of phenol content in sweet potato tissue that made an activation of defense reaction against the rot causal pathogen.As the exposure time to UV-C light increased,a higher content of phenols occurred.Moreover,UV-C application caused decrease in sugar content of root tissue that is flavored by soft rot-causal pathogen.

花魔芋软腐病原真菌分离鉴定

魔芋软腐病是魔芋生产过程中的重要病害,也是限制魔芋产业发展的主要因素。目前,已有报道魔芋软腐病主要由细菌引起,鲜有真菌引起魔芋球茎软腐发病的报道。为明确云南曲靖市花魔芋(Amorphophallus konjac)软腐病的病原种类和侵染特征,该研究通过组织分离法,对采集自云南曲靖市的花魔芋病样进行了真菌的分离,通过形态学结合基于ITS与LSU序列分析的分子鉴定方法对分离真菌进行鉴定,并根据柯赫氏法则进行致病性测定,并对鉴定出的病原真菌同魔芋软腐病原细菌进行了双回接试验分析。结果表明:(1)从形态学和分子水平鉴定了轮纹镰刀菌(Fusarium concentricum)、尖孢镰刀菌(F.oxysporum)和F.ambrosium 3种镰刀菌,1种毛霉属真菌(Mucor sp.),1种根霉属真菌(Rhizopus sp.),1种青霉属真菌(Penicillium sp.)和1种粉红螺旋聚孢霉属真菌(Clonostachys sp.)。(2)统计分析发现,轮纹镰刀菌的相对丰度最高,为45.45%。(3)柯赫氏法则检测发现轮纹镰刀菌具有致病性。(4)轮纹镰刀菌和病原细菌胡萝卜果胶杆菌(Pectobacterium aroidearum)双接种魔芋球茎发现软腐病发病更快,病变组织重量显著高于单接种轮纹镰刀菌或果胶杆菌处理。综上表明,魔芋软腐病可能是由真菌和细菌复合侵染引发。该研究结果为魔芋软腐病的防治提供了理论依据。

新洋葱伯克霍尔德氏菌YM12的分离鉴定及其对黄瓜软腐病的防治效果

黄瓜软腐病是由巴西果胶杆菌Pectobacteriumbrasiliense引起的一种细菌性病害,该病害发生严重且难防难控,以筛选具有高效抑菌作用的生防微生物为目的,本研究在黄瓜根际土壤中分离得到了一株对巴西果胶杆菌具有显著抑制效果的菌株YM12。经形态学观察、生理生化特征测定及多基因系统发育树分析,鉴定其为新洋葱伯克霍尔德氏菌Burkholderia cenocepacia;抗生素合成基因检测结果表明,菌株YM12具有产生硝吡咯菌素pyrrolnitrin与藤黄绿脓菌素pyoluteorin的能力;其他生防性状分析表明,YM12具有溶磷能力,还可产生蛋白酶及嗜铁素。经抑菌谱分析,菌株YM12能够抑制5种病原细菌及3种病原真菌的生长。盆栽试验结果表明,菌株YM12对黄瓜软腐病具有明显的防治效果,防效可达62.84%,优于对照药剂春雷霉素。综上,菌株YM12是目前首次报道的对细菌性软腐病具有良好生防效果的新洋葱伯克霍尔德氏菌。