Fine-mapping of a candidate gene for web blotch resistance in Arachis hypogaea L.

Peanut(Arachis hypogaea L.)is a globally important oil crop.Web blotch is one of the most important foliar diseases affecting peanut,which results in serious yield losses worldwide.Breeding web blotch-resistant peanut varieties is the most effective and economically viable method for minimizing yield losses due to web blotch.In the current study,a bulked segregant analysis with next-generation sequencing was used to analyze an F2:3 segregating population and identify candidate loci related to web blotch resistance.Based on the fine-mapping of the candidate genomic interval using kompetitive allele-specific PCR(KASP)markers,we identified a novel web blotch resistance-related locus spanning approximately 169 kb on chromosome 16.This region included four annotated genes,of which only Arahy.35VVQ3 had a non-synonymous single nucleotide polymorphism in the coding region between the two parents.Two markers(Chr.16.12872635 and Chr.16.12966357)linked to this gene were shown to be co-segregated with the resistance of peanut web blotch by 72 randomly selected recombinant inbred lines(RIL),which could be used in marker-assisted breeding of resistant peanut varieties.

防御假单胞ZF509的分离鉴定及其对甜瓜细菌性果斑病的防治效果研究

为了筛选对瓜类果斑病(acterial fruit blotch,BFB)具有良好拮抗效果的生防细菌,本研究从黑龙江马铃薯根际土壤中分离得到一株对西瓜噬酸菌Acidovorax citrulli具有显著抑制效果的生防菌株ZF509。经形态学观察、生理生化特征、Biolog测定和多基因系统发育树分析,鉴定菌株ZF509为防御假单胞Pseudomonas protegens。经抑菌谱分析,菌株ZF509对4种病原细菌、8种病原真菌具有显著拮抗作用。经酶活检测和抑菌物质分析,ZF509具有溶磷能力,可分泌蛋白酶,合成生物膜,产生氢氰酸,具备2-羟基、2,4-DAPG、藤黄绿脓菌素以及吡咯菌素4种抑菌物质的合成编码基因。盆栽试验结果表明,接种ZF509的处理果斑病发病的病情指数显著降低,防效可达73.46%,显著优于对照药剂噻霉酮处理。综上所述,菌株ZF509对瓜类细菌性果斑病具有良好的生防潜力和应用前景。

外源茉莉酸甲酯诱导大麦叶斑病抗性研究

【目的】探讨不同浓度外源茉莉酸甲酯(MeJA)诱导大麦抗叶斑病效应差异及其分子机制,为应用MeJA防治大麦叶斑病提供理论依据。【方法】以‘蒙啤麦3号’大麦品种幼苗为材料,设置不接菌(无菌水处理叶片)、接菌(无菌水处理叶片接种麦根腐平脐蠕孢菌)和接菌+MeJA(0.5,1.0,1.5,2.0,2.5mmol/LMeJA喷施叶片后接菌)3组处理,于三叶期调查叶斑病发病情况,并据此筛选最适MeJA浓度,然后测定不接菌、接菌及接菌+MeJA(最适浓度)下不同处理时间叶片的抗氧化酶、抗病相关酶活性、丙二醛含量、渗透调节物质含量以及相关基因表达水平。【结果】(1)叶面喷施外源MeJA提高了大麦对叶斑病的抗性,1.5mmol/LMeJA处理叶片的病情指数较对照显著降低19.03%,诱导抗性效果最佳;(2)与单独接菌处理相比,1.5mmol/LMeJA处理大麦叶片超氧化物歧化酶、过氧化物酶、过氧化氢酶、几丁质酶和β-1,3-葡聚糖酶活性均显著提高,而其丙二醛、脯氨酸、可溶性糖和可溶性蛋白含量显著降低,同时受MeJA调控转录因子及编码抗病相关酶的基因表达量显著上调。【结论】外源喷施1.5mmol/LMeJA通过调节抗病相关酶活性和渗透调节物质含量,以及调控抗病相关酶基因及茉莉酸信号途径关键转录因子基因表达,进而提高大麦植株的叶斑病抗性。

19种杀菌剂对甜瓜细菌性果斑病菌的杀菌活性评价

瓜类细菌性果斑病是由西瓜噬酸菌引起的一种种传病害,在生产上的危害极为严重,可造成大面积的减产甚至绝产,但目前在生产中还缺乏有效的防治药剂。为筛选出高效防治细菌性果斑病的杀菌剂,在室内筛选了19种杀菌剂的离体活性成分,并对高活性杀菌剂进行毒力评价和活体盆栽验证。室内研究结果表明,0.3%四霉素水剂等8种杀菌剂离体杀菌活性显著,毒力强度依次为0.3%四霉素水剂>1%申嗪霉素悬浮剂>5%噻霉酮悬浮剂>20%辛菌胺醋酸盐水剂>20%丙硫唑悬浮剂>4%春雷霉素水剂>0.4%蛇床子素水剂>0.5%小檗碱水剂。活体盆栽试验结果表明,0.5%小檗碱水剂、20%丙硫唑悬浮剂、4%春雷霉素水剂和5%噻霉酮悬浮剂这4种药剂对甜瓜细菌性果斑病有较好的防治效果,其中0.5%小檗碱水剂对甜瓜细菌性果斑病的保护和治疗作用最强,在供试质量浓度为100 mg·L^(-1)时的保护和治疗防效分别为79.66%和73.24%。上述研究试验表明,0.5%小檗碱水剂、20%丙硫唑悬浮剂、4%春雷霉素水剂和5%噻霉酮悬浮剂可作为田间防治甜瓜细菌性果斑病的有效候选药剂。

海南省东方市甜瓜细菌性果斑病病原鉴定

细菌性果斑病严重影响甜瓜生产,为确定其病原菌种类,从海南省东方市种植基地采集大量疑似细菌性果斑病的甜瓜样本,进行病原菌分离纯化,并按柯赫法则对获得的菌株进行致病性测定。通过菌落形态观察、生理生化测定及16S rDNA序列比对分析,对分离病原菌进行鉴定。结果表明,大田采集的所有甜瓜病果中均分离到培养性状一致的细菌,细菌分离率为100%;所有分离菌株均对甜瓜果实具有致病性,该病原菌革兰氏反应呈阴性,其菌落形态及生理生化测定结果与已报道的西瓜嗜酸菌(Acidovorax citrulli)一致;BLAST比对与A. citrulli菌株的同源性可达100%,系统发育分析也进一步证实该病菌为A. citrulli。研究结果确定了甜瓜果斑病的致病菌,为该病的有效防治提供了依据。

13种药剂种子处理对瓜类细菌性果斑病的防治效果

瓜类细菌性果斑病是西瓜、甜瓜等瓜类作物的重要细菌性病害。为筛选防控果斑病的有效药剂,本研究比较了13种药剂浸种带菌西瓜种子不同时间对果斑病的防治效果及对种子发芽的影响;并通过“先喷药后接种”和“先接种后喷药”,比较了13种药剂对西瓜苗期果斑病的预防和治疗效果,同时测定了助剂8.6%聚乙二醇对13种药剂的增效作用。药剂浸种试验结果表明,带菌种子在10%阿苯达唑750倍液、2%春雷霉素300倍液中浸种12 h,对果斑病的防效均达到100%,发芽率比清水浸种分别高16.20百分点和16.34百分点;杀菌剂1号200倍液处理12 h的防效较好,为85.58%,且促进种子萌发。苗期喷施药剂的试验结果表明,13种药剂对果斑病的预防效果均好于治疗效果,预防效果和治疗效果都超过60%的药剂有7种,以10%阿苯达唑600倍液对果斑病的防效最好,预防效果和治疗效果分别为87.58%和75.70%,与8.6%聚乙二醇混配后分别提高至94.12%和81.31%,增效作用显著。本研究结果为后续田间试验和大面积推广应用提供了技术支撑。

新的柑橘叶斑驳病毒桑树分离株的基因组克隆及传播方式分析

柑橘叶斑驳病毒(citrus leaf blotch virus,CLBV)可侵染多种植物。2018年,通过对叶片表现为皱缩、变窄症状的桑叶样品进行高通量测序后发现,桑树中存在CLBV的侵染。通过RT-PCR、5′-和3′-RACE等方法确定了CLBV桑树分离株(CLBV-MA)的全基因组序列。CLBV-MA基因组全长8617 nt(不包含3′polyA尾),共包含3个开放阅读框,分别编码复制酶蛋白、运动蛋白和外壳蛋白。CLBV-MA与其他CLBV分离株编码的复制酶蛋白以及外壳蛋白的氨基酸序列相似性分别为79.0%~89.1%、87.6%~94.7%,是一个新分离株。基于全基因组核苷酸序列的系统进化分析显示,CLBV-MA与CLBV-Actinidia、CLBV-HZ、CLBV-XL、CLBV-Actinidia-V20以及CLBV-ML聚类到一个分支,亲缘关系最近,并且CLBV-MA更为原始。根据桑树的繁殖方式、修剪管理方式、树龄以及CLBV-MA在桑园中的分布情况分析,CLBV-MA主要通过嫁接传播,也可以通过被污染的刀具传播,但传播效率低下。CLBV-MA全基因组序列及其传播方式的确定,为建立CLBV-MA分子检测方法及制定有效的防控措施奠定了基础。

基于表型聚类和CDDP标记的牡丹花瓣色斑遗传多样性分析

【目的】采用色斑表型性状分析和保守DNA序列多态性(conserved DNA-derived polymorphism,CDDP)分子标记技术相结合的方法,揭示牡丹花瓣基部色斑的遗传起源。【方法】利用19个色斑表型性状和CDDP分子标记对191份牡丹材料的花瓣色斑进行遗传多样性分析,利用Origin软件进行表型性状变异分析和系统聚类,采用PopGene 2.4软件计算分子标记多样性指数和多态性位点率等,利用NTSYS软件非加权组平均法(UPGMA)绘制聚类树状图,并进行一致检测和Mantel检测。【结果】牡丹色斑表型变异分析结果表明:牡丹花瓣色斑性状发生了强变异,尤其是色斑颜色变异系数较大。表型性状聚类结果显示,紫斑牡丹与其他种或品种牡丹交集较多,且与西北牡丹品种关系最为密切。利用17条CDDP引物扩增191份牡丹材料的花瓣DNA,共扩增出401条条带,多态性位点率达到96.91%。在色斑群体水平上,有效等位基因数为1.3759,Nei’s基因多样性指数为0.2122,Shannon-Wiener信息指数为0.3324,说明牡丹花瓣色斑在分子水平上具有丰富的遗传多样性。聚类结果显示,紫斑牡丹和卵叶牡丹、四川牡丹聚在一起,三者亲缘关系较近,紫斑牡丹对现有牡丹栽培品种的色斑性状产生了较大影响,可能是牡丹品种色斑的主要来源。将表型性状聚类和CDDP分子标记聚类的遗传矩阵进行Mantel检验,得出相关系数为0.55,表明两种聚类结果有相似之处,均能很好地体现牡丹花瓣色斑的遗传来源。【结论】紫斑牡丹是牡丹品种色斑的主要来源,卵叶牡丹和四川牡丹也对牡丹品种色斑的形成有影响。

Screening and Identification of Antagonistic Bacterium ZG-10 against Spot Blotch Disease in Pakchoi

[ Objective] The purpose was to screen bacterium with antagonistic effect against pathogen of spot blotch disease in pakchoi in vegetable field. [Method] More than 200 strains of bacteria which could produce spore were isolated from soil in different places. Through screening and rescreening, the bacteria with higher antibacterial activity were conducted observation about thallus shapes and colony characters, a series of physiological and biochemical tests were performed. [Result] Rescreening results indicated that the strains including ZG-10, ZG-19, ZG-59, ZG-72 and ZG-31 had significant antibacterial activity, which had very high research value and good application prospect for biocontrol on spot blotch disease in pakchoi; the strain ZG-10 was identified to be Bacillus subtilis. [ Conclusion] The strain ZG-10 had biocontrol potential and good development prospect. This research laid certain basis for subsequent research and strated a new way for the application of antagonistic strain and proteinum polypeptide in agdculture.

The Relationship between Diseases Index of Septoria Leaf Blotch, Leaf Rust and Yield Losses in Bread Wheat Cultivar in Albania

Both grain yield and disease performance are important factors to consider for winter wheat （Triticum aestivum） cultivar selection. However, disease index and yield data are often presented separately, making it difficult to compare values across multiple environments. Two-year investigations （2009-2010）, in which eight common wheat lines/genotypes were included to test their susceptibility against wheat LR （leaf rust） Puccinia triticina f. sp. tritici Roberge ex Desm., and the SLB （SeptoriaJStagonospora leaf blotch） complex Septoria tritici Desm. and Stagonospora nodorum, were carried out in the experimental field of ATTC （Agriculture Technology Transfer Centre） of Lushnje （Albania）. The objective of this study was to use a rank-based method to compare cultivars based on yield and disease performance combined across multiple environments. Analysis of variance revealed the presence of an important and significant variability in the experimental materials used to evaluate the susceptibility and the resistance of common wheat lines against SLB and LR. There were high negative correlations between yieldS, tritici （0.6683） and yield--P, recondita f. sp. tritici （0.5261）. The negative effects of two pathogens have shown ＂the parallel＂/similar negative influences on yield trait and there was a high positive correlation （0.7631） between S. tritici and P. recondita f. sp. tritici. According to study results the lines Regina × L-776, IKB-P6 and Bullgar 3 × KB 703 have shown good results of resistance （R） level against S. tritici and P. recondita f. sp. tritici.

生防芽孢杆菌与杀菌剂复配对苹果斑点落叶病菌的联合毒力

[目的]为苹果斑点落叶病的防控提供新的杀菌剂及其增效组合。[方法]采用对峙培养法筛选生防菌,菌丝生长速率法筛选化学杀菌剂,Horsfall法确定菌药复配比例。[结果](1)7种化学杀菌剂均对病菌有较强的抑制活性,其中戊唑醇、苯醚甲环唑和丙环唑3种药剂对病菌抑制效果最佳,EC50分别达0.21、0.30和0.81μg/mL;其次为吡唑醚菌酯、代森锰锌和嘧菌酯;多菌灵的抑菌效果最差,EC50为15.03μg/mL。(2)3种芽孢杆菌中解淀粉芽孢杆菌(Bacillus amyloliquefaciens)SJ1606的抑菌效果最好,其发酵上清液和发酵上清粗提物对病菌的EC50分别为2.38μL/mL和0.53μL/mL。(3)解淀粉芽孢杆菌SJ1606发酵上清液粗提物和代森锰锌、吡唑醚菌酯的复配均表现为增效作用,其中体积比6∶4和7∶3达最大毒性比,分别为1.39和1.41。[结论]戊唑醇、苯醚甲环唑和丙环唑对苹果斑点落叶病菌的毒力最大;解淀粉芽孢杆菌SJ1606发酵上清液粗提物对化学杀菌剂代森锰锌和吡唑醚菌酯具有增效作用,为后续农药新制剂研发提供了参考数据。

Complete genome sequences of four isolates of Citrus leaf blotch virus from citrus in China

Citrus leaf blotch virus （CLBV） is a member of the genus Citrivirus, in the family Betaflexiviridae. It has been reported CLBV could infect kiwi, citrus and sweet cherry in China. Of 289 citrus samples from six regions of China, 15 were detected to be infected with CLBV in this study. The complete genome of four isolates of CLBV was obtained from Reikou in Sichuan （CLBV-LH）, Yura Wase in Zhejiang （CLBV-YL）, Bingtangcheng in Hunan （CLBV-BT）, Fengjie 72-1 in Chongqing （CLBV- F J）, respectively. While they all represented 8 747 nucleotides in monopartite size, excluding the poly（A） tail, each of the isolates coded three open reading frames （ORFs）. Identity of the four isolates ranged from 98.9 to 99.8% to each other and from 96.8 to 98.1% to the citrus references in GenBank by multiple alignment of genomes. A phylogenetic tree based on the genome sequences of available CLBV isolates indicated that the four isolates were clustered together, suggesting that CLBV isolates from citrus in China did not have obvious variation. This is the first report of the complete nucleotide sequences of CLBV isolates infecting citrus in China.

Detection of Apple Marssonina Blotch with PLSR, PCA, and LDA Using Outdoor Hyperspectral Imaging

In this study, hyperspectral images were used to detect a fungal disease in apple leaves called Marssonina blotch(AMB). Estimation models were built to classify healthy, asymptomatic and symptomatic classes using partial least squares regression(PLSR), principal component analysis(PCA), and linear discriminant analysis(LDA) multivariate methods. In general, the LDA estimation model performed the best among the three models in detecting AMB asymptomatic pixels, while all the models were able to detect the symptomatic class. LDA correctly classified asymptomatic pixels and LDA model predicted them with an accuracy of 88.0%. An accuracy of 91.4% was achieved as the total classification accuracy. The results from this work indicate the potential of using the LDA estimation model to identify asymptomatic pixels on leaves infected by AMB.

Development and characterization of new allohexaploid resistant to web blotch in peanut

Peanut diseases seriously threaten peanut production, creating disease-resistant materials via interspecific hybridization is an effective way to deal with this problem. In this study, the embryo of an interspecific F1 hybrid was obtained by crossing the Silihong(Slh) cultivar with Arachis duranensis(ZW55), a diploid wild species. Seedlings were generated by embryo rescue and tissue culture. A true interspecific hybrid was then confirmed by cytological methods and molecular markers. After treating seedlings with colchicine during in vitro multiplication, the established interspecific F1 hybrid produced seeds which were named as Am1210. With oligonucleotide fluorescence in situ hybridization(Oligo FISH), molecular marker evaluations, morphological and web blotch resistance characterization, we found that: 1) Am1210 was an allohexaploid between Slh and ZW55;2) the traits of spreading lateral branches, single-seeded or double-seeded pods and red seed coats were observed to be dominant compared to the erect type, multiple-seeded pods and brown seed coats;3) the web blotch resistance of Am1210 was significantly improved than that of Slh, indicating the contribution of the web blotch resistance from the wild parent A. duranensis. In addition, 69 dominant and co-dominant molecular markers were developed which could be both used to verify the hybrid in this study and to identify translocation or introgression lines with A. duranensis chromosome fragments in future studies as well.

Overview of purple blotch disease and understanding its management through chemical, biological and genetic approaches

Purple blotch disease of Allium spp. crops caused by Alternaria porri has remained a major concern in agriculture for both farmers and research fraternity as it severely damages the crops and drastically reduces the yield. The symptoms appear after 1–4 days of infection and bulb rot begin, and eventually turn into dark reddish-purple and then brownish/black lesions. Many factors like season, time of sowing, humidity and temperature, stage of crop, and plant architecture have a huge impact on the progression of purple blotch disease. Many genic markers based on amplification of an Alta1 gene sequence have been designed for identification and differentiation of different Alternaria species groups. Among the most commonly used fungicides, mancozeb, tebuconazole, difenaconazole and azoxystrobin were found to be the ideal for the management of purple blotch disease and increased garlic yield. Many biological approaches such as plant extracts and bio-control agents were found partially effective for controlling the disease. A report on QTL mapping for purple blotch resistance discovered that purple blotch resistance is controlled by a single dominant gene ApR1. To completely understand the purple blotch disease resistance for crop improvement, a study is required at transcriptome level for hunting purple blotch resistant genes by gene annotation and mining. Genetic engineering and genome editing are other approaches that can be done for engineering disease resistance in Allium crops for genetic improvement.

Application of Pyroligneous Acid in the Prevention and Control of Brown Blotch Disease in Pleurotus ostreatus

In the present study, agar diffusion test and field trials were carried out using a mushroom （Pleurotus ostreatus） culti- var Shouyanping as the experimental material to determine the antibacterial activity of refined pyroligneous acid prepared from almond shell against Pseudomonas tolaasfi and its effects on mycelial growth of mushroom. The results revealed that 1.25%, 2.50% and 5.00% of refined pyroligneous acid obviously inhibited the occurrence of brown blotch disease in mushroom, but also greatly promoted mushroom mycelial growth. Therefore, 1.25% and 2.50% of refined pyroligneous acid can be used in fields to prevent brown blotch disease, and 5.00% refined pyroligneous acid can be used to control the incidence of brown blotch disease when it widely occurs in fields.

Breeding of a New High-yield, High-oil and Web Blotch-resistant Big Peanut Variety Shanghua 511

Shanghua 511 is a high-yield, high-oil and web blotch-resistant big peanut variety bred by the Shangqiu Academy of Agriculture and Forestry Sciences through sexual hybridization （Yuhua 18♀×Shangyan 9658♂）. In the wheat-peanut interplanting regional experiment conducted in Henan Province during 2012-2013, the average pod and seed yield of Shanghua 511 were 5906.19 and 4149.3 kg/hm2, respectively. In the wheat-peanut interplanting production experiment conducted in Henan Province in 2013, the average pod and seed yield of Shanghua 511 were 6036.45 and 4309.50 kg/hm2, respectively. In the kernels of Shanghua 511, the contents of crude fat, oleic acid and linoleic acid were 56.62%, 44.9% and 33.4% respectively, and the oleic/linoleic acid ratio was 1.34. This variety had high resistance to web blotch and medium resistance to leaf spot, viral diseases, root rot and collar rot. The 100-pod weight, 100-kernel weight, shelling percentage and growth period of Shanghua 511 were 270.6, 110.9 g, 70.6% and 120 d, respectively. Shanghua 511 passed the approval of Henan Provincial Crop Variety Approval Committee in August, 2015, and is suitable for spring sowing and wheat interplanting in the surrounding area of Henan Province and the area to the north of Huaihe River.

A Comparative Analysis of Culture Media for Optimizing the Mycelial Growth and Sporulation of Stemphylium vesicarium Cause of White Blotch of Onion

This study was conducted to identify a cheap and suitable culture medium for the mycelial growth and sporulation of Sternphylium vesicarium and to determine the cultural and morphological variability of this pathogen. A total of 24 isolates of S. vesicarium collected from eight different onion growing areas were characterized in terms of cultural and morphological aspects. Front colony colors were greenish brown to dirty white, deep grey to whitish, light grey to whitish, deep greenish white, light grey and dirty white to greenish. Reverse colony colors were brown, deep brown and light brown. Colony shapes were circular and irregular with umbonate, raised and flat type colony elevation. Colony textures were cottony, fluffy and velvety with entire, undulate and filiform type colony margin. Among the culture media, V-7 juice agar found to be the most suitable culture media for mycclial growth of S. vesicarium. The sporulation of the fungus was remarkably influenced by V-7 juice mixed with potato dextrose agar （PDA） media, this media exhibited the highest sporulation （87.76-169.0/mm^2） of S. vesicariumin comparison with other media. The minimum days （28 d to 31 d） for conidial production were observed on V-7 juice agar medium. The length of conidia varied from 14.6 μm to 30.6 μm. The maximum mean length of conidia was 29.97 μm found in isolate DSSA, while the minimum mean length 17.36 μm was found in isolate MSMM 02. The breadth of conidia ranged from 4.7 μm to 15.7μm. The maximum mean breadth of conidia was 12.55 μm found in the isolate DSSA, while the minimum mean breadth 9.760 μm was found in the isolate CCKH 02. The horizontal septation varied from l to 3 and the longitudinal septation varied from 0 to 4.

瓜类细菌性果斑病菌拮抗细菌的筛选及其抑菌作用

从土壤中筛选出抑制哈密瓜细菌性果斑病的拮抗菌株,明确其分类地位,测定其生长条件及防病效果。采用梯度稀释法及平板对峙法进行菌株的分离及筛选,综合形态学观察、生理生化测定以及分子鉴定等多方面对菌株进行鉴定,确定生防菌种属,并测定其最适生长条件,利用平板对峙法测定其抑菌作用,并分别采用针刺接种法、叶面喷施法对生防菌的离体叶片和盆栽防病试验进行测定。本研究从土样中共分离出196株细菌,经对峙筛选发现有20株细菌具有抑菌效果,其中编号为131、791的两株细菌对哈密瓜细菌性果斑病病原菌具有较好的平板拮抗效果,抑菌圈直径分别为(19.03±0.13)mm,(17.55±0.29)mm。经鉴定菌株131为沙福芽孢杆菌(Bacillus safensis),菌株791为贝莱斯芽孢杆菌(B.velezensis)。菌株131的最适生长条件为NB培养基,培养18 h,温度37℃,pH 7,接种量为2%。菌株791的最适生长条件为KB培养基,培养18 h,温度37℃,pH 6,接种量为1%。菌株131和791对哈密瓜细菌性果斑病的离体叶片防效分别为83.33%和87.53%,室内盆栽防效分别为69.86%和77.99%,同时也对多种病原真菌具有抑制作用。菌株131和791均为对哈密瓜细菌性果斑病具有较好防效的芽孢杆菌(Bacillus),对瓜类作物细菌性果斑病的防治提供了理论补充,奠定了果斑病害生物防治的基础。

<i>In-Vivo</i>Management of Purple Blotch of Onion Caused by <i>Alternaria porri</i>(Ellis) Cif. through Fungicides

An experiment was carried out to study the outcome of environmental factors (Temperature, Relative Humidity, Rainfall) and management of the purple blotch disease of onion using five treatments (Rovral + Ridoil gold with 3,4,5,6 sprays and control). The Taherpuri variety was used during the 2015-2016 cropping seasons at BARI, Gazipur, Bangladesh. In the experiment, the purple blotch disease surfaced at the end of January 2016 and was severe in late February to March (PDI 76.12%) due to temperature and RH above 24°C and 95%, respectively. As for the chemical control, the PDI for the treatments ranged from 50.66% to 83.33%. Significantly higher stem height was recorded by T4 (68.06 cm), where six sprays of Rovral + Ridomil were applied. The minimum stem height was recorded in T5 (59.23 cm). The maximum stem number per hill was recorded in T4 (2.30) numerically but differed significantly with T5 (2.00), where fungicides were not applied. The maximum lesion area was measured in T5 (25.26 mm2). Regarding PDI (Percent disease index), there was a significant difference among the treatments. The PDI value on purple blotch of onion ranged from 34.00 to 83.33. The lowest PDI was assessed in T4 (34.00). Statistical analysis revealed that a significant decrease of PDI on purple blotch was recorded under treatments of T1, T2, T3, and T4 (39.20%, 45.60%, 49.59%, and 59.19%) on controlling the disease and giving the optimum yield but all of them significantly differed with T5 (83.33%) where no fungicides were sprayed.