Host specificity,pathogenicity and the presence of virulence genes in Iranian strains of Pseudomonas syringae pv. syringae from different hosts

Pseudomonas syringae pv. syringae (Pss) strains were isolated from almond, apricot, peach, pear, sweet cheery and wheat in Kohgiluye and Boyer-Ahmad, Kordestan, Fras and Chaharmahal and Bakhtiari provinces of Iran. The strains were examined for host specificity, the presence of virulence genes and pathogenicity on different hosts. After inoculation of isolates, in compatible reactions bacterial populations increased within six days of inoculation and final cell numbers increased several-fold over initial inoculum levels, but in incompatible reactions, bacterial populations declined within four days of inoculation. Almond, sweet cherry and wheat isolates induced progressive necrotic symptoms on almond leaves and stems. Apricot, peach and sweet cherry isolates induced necrotic lesions when inoculated on apricot leaves. On pear leaves and stems, only the pear isolate incited pathogenic reaction and isolates from other hosts did not. The syrB gene was detected in all of the tested isolates. Almond and pear isolates did not have the syrD gene. The sypA gene was detected in the almond, peach, pear and sweet cherry isolates while the sypB gene was detected in the apricot, peach, sweet cherry and wheat isolates. Almond, apricot, pear and wheat isolates gave negative results for the detection of nit gene. The gene Ach, was detected only in the peach isolate and gene hrmA, was detected only in the wheat isolate. This study indicates that host specificity exists among different Pss strains, and genes responsible for syringomycin and syringopeptin production contribute to the virulence of Pss strains.     

Morphological and Inter Simple Sequence Repeat (ISSR) Markers Analyses of Corynespora cassiicola Isolates from Rubber Plantations in Malaysia

Morphological features and Inter Simple Sequence Repeat (ISSR) polymorphism were employed to analyse 21 Corynespora cassiicola isolates obtained from a number of Hevea clones grown in rubber plantations in Malaysia. The C. cassiicola isolates used in this study were collected from several states in Malaysia from 1998 to 2005. The morphology of the isolates was characteristic of that previously described for C. cassiicola. Variations in colony and conidial morphology were observed not only among isolates but also within a single isolate with no inclination to either clonal or geographical origin of the isolates. ISSR analysis delineated the isolates into two distinct clusters. The dendrogram created from UPGMA analysis based on Nei and Li's coefficient (calculated from the binary matrix data of 106 amplified DNA bands generated from 8 ISSR primers) showed that cluster 1 encompasses 12 isolates from the states of Johor and Selangor (this cluster was further split into 2 sub clusters (1A, 1B), sub cluster 1B consists of a unique isolate, CKT05D); while cluster 2 comprises of 9 isolates that were obtained from the other states. Detached leaf assay performed on selected Hevea clones showed that the pathogenicity of representative isolates from cluster 1 (with the exception of CKT05D) resembled that of race 1; and isolates in cluster 2 showed pathogenicity similar to race 2 of the fungus that was previously identified in Malaysia. The isolate CKT05D from sub cluster 1B showed pathogenicity dissimilar to either race 1 or race 2.     

Gerbera jamesonii, Osteospermum sp. and Argyranthemum frutescens: New Hosts of Fusarium oxysporum f. sp. chrysanthemi

The pathogenicity of five isolates of Fusarium oxysporum obtained from infected gerbera (Gerbera jamesonii), chrysanthemum (Chrysanthemum morifolium), Paris daisy (Argyranthemum frutescens) and African daisy (Osteospermum sp.) plants was tested on some varieties of the following Compositae hosts: C. morifolium, G. jamesonii, Argyranthemum frutescens (Paris daisy) and Osteospermum sp. and compared with the host range and pathogenicity of an isolate of F. oxysporum f. sp. chrysanthemi obtained from the ATCC collection. The results indicated that isolates of F. oxysporum from G. jamesonii as well as those from A. frutescens and Osteospermum sp. belong to the forma specialischrysanthemi. The isolate from gerbera was virulent on all tested varieties of gerbera, C. morifolium, A. frutescens and Osteospermumsp. Similar results were obtained testing the isolates obtained from A. frutescens and Osteospermumsp. The strain from C. morifolium infected cultivar of gerbera, A. frutescens and Osteospermum sp. The pathogenicity of isolate of F. oxysporum f. sp. chrysanthemi obtained from the ATCC showed a different cultivar range particularly in the case of chrysanthemum and gerbera.     

Epichloë typhina from toxic tall fescue grasses.

Epichloë typhina, a clavicipitaceous systemic phytopathogen, was isolated from two varieties and three hybrids of tall fescue (Festuca arundinaceae). The morphology of the fescue isolates was compared with E. typhina isolated from bent grass (Agrostis perennans). In all isolates, conidia were identical and were typical of E. typhina. In fescue grasses the endophyte failed to produce stromata, but on bent grass the fungus seasonally produced stromata, typical of the genus. Cattle grazing the fescue grasses showed signs of the fescue toxicity syndrome, the E. typhina was found in frequencies of 100%; in grasses from pastures in which cattle showed no signs of the syndrome, frequencies were 0 to 50%. Nutritional factors in vitro were more complex for the isolates from fescue than for the isolate from bent grass. These studies suggested that E. typhina includes biotypes that might be involved in the toxicity syndrome. The fescue biotypes grew poorly on media, and yields were inadequate for toxicity studies. However, the bent grass isolate grew well on three media, and extracts from two of these were toxic to chicken embryos. All isolates produced in vitro the nontoxic fungal steroid tetraenone [ergosta-4,6,8(14),22-tetraen-3-one], which has been isolated from toxic fescue grasses.     

Characterization of Pratylenchus penetrans from Ten Geographically Isolated Populations Based on Their Reaction on Potato

Single female cuhures of Pratylenchus penetrans were established from soil and root samples collected from 10 geographically isolated locations in North America. The resultant isolates were used to evaluate nematode egression from and multiplication on roots of potato clones to distinguish intraspecific differences among isolates. The 10 nematode isolates were statistically separated into four groups based on percentage of nematodes that egressed from the P. penetrans-resistant potato done L 118-2. The Cornell (CR), Wisconsin (WI), Long Island (LI), and Adirondack (AD) isolates, selected as representative isolates of each of the four groups, exhibited 53%, 39%, 25%, and 10% egression from L118-2, respectively. Reproduction of these four isolates was measured on three potato cultivars (Russet Burbank, Butte, and Hudson) and two breeding lines (NY85 and L118-2). The LI and AD isolates reproduced well on all five potato clones. The CR isolate reproduced well on Russet Burbank and NY85 but significantly less on Butte, Hudson, and L118-2. Reproduction of the WI isolate was less than the LI and AD isolates but more than the CR isolate on all potato clones tested except Russet Burbank. Reproduction of the WI isolate on Russet Burbank was less than the other three isolates. Based on these results, four distinct intraspecific variants of P. penetrans are proposed: Cornell, Wisconsin, Long Island, and Adirondack.     

Comparative genome hybridization reveals substantial variation among clinical isolates of Borrelia burgdorferi sensu stricto with different pathogenic properties

Clinical and murine studies suggest that there is a differential pathogenicity of different genotypes of Borrelia burgdorferi, the spirochetal agent of Lyme disease. Comparative genome hybridization was used to explore the relationship between different genotypes. The chromosomes of all studied isolates were highly conserved (>93%) with respect to both sequence and gene order. Plasmid sequences were substantially more diverse. Plasmids lp54, cp26, and cp32 were present in all tested isolates, and their sequences and gene order were conserved. The majority of linear plasmids showed variation both in terms of presence among different isolates and in terms of sequence and gene order. The data strongly imply that all B. burgdorferi clinical isolates contain linear plasmids related to each other, but the structure of these replicons may vary substantially from isolate to isolate. These alterations include deletions and presumed rearrangements that are likely to result in unique plasmid elements in many isolates. There is a strong correlation between complete genome hybridization profiles and other typing methods, which, in turn, also correlate to differences in pathogenicity. Because there is substantially less variation in the chromosomal and circular plasmid portions of the genome, the major differences in open reading frame content and genomic diversity among isolates are linear plasmid driven.     

球孢白僵菌不同分离株的生物学及对小猿叶甲成虫致病性测定

球孢白僵菌Beauveriabassiana是一种寄主范围广、致病性强、适应性广的昆虫病原真菌。对采自广东阳山小猿叶甲Phaedonbrassicae的球孢白僵菌 6个分离株 (A ,B ,C ,D ,E ,F)的菌落生长速率、产孢量、分生孢子萌发率进行了实验 ,测定和比较了这 6个分离株对小猿叶甲成虫的致病力。结果表明 :各分离株在菌落生长速率上没有显著差异 ,但各分离株的孢子萌发率有显著差异 ,其中C ,D ,E分离株产孢量明显高A ,F分离株。用 5× 1 0 7分生孢子 mL的悬浮液处理小猿叶甲成虫 ,分离株间的致病力有显著的差异 ,以D分离株对小猿叶甲成虫的感染死亡率最高 ,为 86 67%。综合比较 ,产孢量和致病性较高的D分离株可作为进一步研究的材料。     

Eleven new sequence variants of citrus exocortis viroid and the correlation of sequence with pathogenicity.

Full-length double-stranded cDNA was prepared from purified circular RNA of two new Australian field isolates of citrus exocortis viroid (CEV) using two synthetic oligodeoxynucleotide primers. The cDNA was then cloned into the phage vector M13mp9 for sequence analysis. Sequencing of nine cDNA clones of isolate CEV-DE30 and eleven cDNA clones of isolate CEV-J indicated that both isolates consisted of a mixture of viroid species and led to the discovery of eleven new sequence variants of CEV. These new variants, together with the six reported previously, form two classes of sequence which differ by a minimum of 26 nucleotides in a total of 370 to 375 residues. These two classes correlate with two biologically distinct groups when propagated on tomato plants where one produces severe symptoms and the other gives rise to mild symptoms. Two regions of the native structure of CEV, comprising 18% of the total residues, differ between the sequence variants of mild and severe isolates. Whether or not both of these regions are essential for the variation in pathogenicity has yet to be determined.     

致病疫霉超级生理小种遗传多样性分析

通过交配型和甲霜灵抗性以及线粒体DNA单倍型、SSR和AFLP基因型分析对40个超级生理小种菌株进行了遗传多样性分析。在被测菌株中发现了A1、A2和自育3种不同类型的交配型。其中,A1和自育型菌株数量多,分别为21株和14株,而A2交配型仅5株。甲霜灵抗性测定检测出高抗菌株26株,敏感菌株14株。线粒体DNA单倍型测定出Ia型和IIa型两种,比例接近1:1。基于5个基因座被测40个超级生理小种菌株共鉴定出了7种SSR基因型。利用6对荧光引物共检测到258条AFLP谱带,其中多态性谱带204条,多态性为79.1%。将供试的40个菌株划分为38个基因型,几乎每个菌株都为1个特有基因型。而且,我国南方和北方超级生理小种群体存在着明显的遗传差异。结果表明我国致病疫霉超级生理小种具有丰富的遗传多样性,可以推断致病疫霉中的任何小种都可在多个抗病基因的强大选择压力下,在短时间内通过与之对应的无毒基因快速突变而成为超级生理小种。当前对致病疫霉生理小种的鉴定及监测对生产上利用抗病品种防控晚疫病的指导意义不大。     

Pathogenicity of Fusarium graminearum Chemotypes Towards Corn, Wheat, Triticale and Rye

The pathogenicity of nine Fusarium graminearum isolates belonging to three different trichothecene-producing chemotypes, i.e. NIV + FUS, DON + 3-AcDON, and DON + 15-AcDON was tested on corn, wheat, triticale and rye. Although these compounds are known to have different toxicity, no difference in pathogenicity was observed among the mean values for chemotypes. However, within each chemotype there were isolates with different pathogenicity which was not correlated with the ability to produce trichothecenes in vitro. The pathogenicity of each isolate was almost the same for all tested cereals. The involvement of trichothecenes in pathogenesis was investigated in infected corn stalk tissues. All the expected trichothecenes were detected with the exception of NIV and FUS.     

Monoclonal antibody analyses of cytopathic and noncytopathic viruses from fatal bovine viral diarrhea virus infections.

A panel of monoclonal antibodies that recognize the two major glycoproteins of bovine viral diarrhea virus (BDV) was used to evaluate the antigenic relationship between cytopathic (CP) and noncytopathic (NCP) viruses isolated from cattle dead or dying from fatal BDV infections. Various unrelated BDV isolates were initially screened by indirect immunofluorescence with monoclonal antibodies directed against the 56- to 58- and 48-kilodalton glycoproteins of the virus. A wide spectrum of reactivity that was independent of biotype was found. Biological clones of the same isolate showed only minor variations from the parental isolate, as did isolates taken from different animals located on the same farm. A similar analysis was repeated with pairs of CP and NCP viruses isolated from 16 unrelated clinical cases of BDV infection resulting in fatal disease. The reactivity patterns within individual pairs of isolates taken from the same animals were in most instances very similar and in some cases indistinguishable from one another. The results demonstrate that antigenic similarity between biotypes is a consistent finding in animals dying from fatal BDV infections. In view of the wide degree between biotypes is a consistent finding in animals dying from fatal BDV infections. In view of the wide degree of variation in reactivity patterns between unrelated BDV isolates, the close antigenic similarity of CP BDV to the homologous NCP BDV of a given pair strongly suggests that CP BDV arises by mutation from NCP BDV.     

Application of comparative phylogenomics to study the evolution of Yersinia enterocolitica and to identify genetic differences relating to pathogenicity

Yersinia enterocolitica, an important cause of human gastroenteritis generally caused by the consumption of livestock, has traditionally been categorized into three groups with respect to pathogenicity, i.e., nonpathogenic (biotype 1A), low pathogenicity (biotypes 2 to 5), and highly pathogenic (biotype 1B). However, genetic differences that explain variation in pathogenesis and whether different biotypes are associated with specific nonhuman hosts are largely unknown. In this study, we applied comparative phylogenomics (whole-genome comparisons of microbes with DNA microarrays combined with Bayesian phylogenies) to investigate a diverse collection of 94 strains of Y. enterocolitica consisting of 35 human, 35 pig, 15 sheep, and 9 cattle isolates from nonpathogenic, low-pathogenicity, and highly pathogenic biotypes. Analysis confirmed three distinct statistically supported clusters composed of a nonpathogenic clade, a low-pathogenicity clade, and a highly pathogenic clade. Genetic differences revealed 125 predicted coding sequences (CDSs) present in all highly pathogenic strains but absent from the other clades. These included several previously uncharacterized CDSs that may encode novel virulence determinants including a hemolysin, a metalloprotease, and a type III secretion effector protein. Additionally, 27 CDSs were identified which were present in all 47 low-pathogenicity strains and Y. enterocolitica 8081 but absent from all nonpathogenic 1A isolates. Analysis of the core gene set for Y. enterocolitica revealed that 20.8% of the genes were shared by all of the strains, confirming this species as highly heterogeneous, adding to the case for the existence of three subspecies of Y. enterocolitica. Further analysis revealed that Y. enterocolitica does not cluster according to source (host).     

Molecular and Pathogenic Variation Identified Among Isolates of <Emphasis Type="Italic">Corynespora cassiicola</Emphasis>

Pathogenicity tests and inter simple sequence repeat (ISSR) molecular fingerprinting markers were utilized to analyze 24 Corynespora cassiicola isolates obtained from a lot of Hevea clones grown in most rubber nurseries and a few plantations in China. The C. cassiicola isolates were collected from Hainan and Yunnan provinces, China, from 2006 to 2008. The assay of 24 C. cassiicola isolates on detached leaves of four different Hevea rubber clones (genotypes PR 107, Dafeng 95, RRIM 600, and Reyan 7-33-97) indicated that 23 of the isolates were susceptible to RRIM 600, and were therefore considered race 1 except for CC-023. ISSR analysis grouped 24 C. cassiicola isolates into four clusters (A, B, C, and D). Unweighted pair-group method with arithmetic averaging (UPGMA) analysis based on Nei and Li's coefficient (calculated from the binary matrix data of 103 DNA fragments generated from 16 ISSR primers) indicated that cluster A included 19 isolates from Hainan and Yunnan (this cluster was further divided into two sub clusters (I, II), sub cluster II contained isolate CC-023); clusters B and C comprised of 1 isolates from Hainan, respectively; while cluster D encompassed 3 isolates from Hainan and Yunnan. Pathogenicity tests and ISSR analysis showed that there was no correlation between race structure, the geographical origin of the pathogen and their ISSR clusters because 23 of the isolates belonging to four distinct clusters were considered race 1 except for isolate CC-023. However, most of the isolates with different pathogenicity levels shared the same clades, and furthermore, the ISSR clusters and cology color had an exact correlation. These results should facilitate the development of rubber clones with enhanced resistance against all genetic clusters of C. cassiicola.     

Genetic variation in a host-parasite association: potential for coevolution and frequency-dependent selection

Abstract.— Models of host‐parasite coevolution assume the presence of genetic variation for host resistance and parasite infectivity, as well as genotype‐specific interactions. We used the freshwater crustacean Daphnia magna and its bacterial microparasite Pasteuria ramosa to study genetic variation for host susceptibility and parasite infectivity within each of two populations. We sought to answer the following questions: Do host clones differ in their susceptibility to parasite isolates? Do parasite isolates differ in their ability to infect different host clones? Are there host clone‐parasite isolate interactions? The analysis revealed considerable variation in both host resistance and parasite infectivity. There were significant host clone‐parasite isolate interactions, such that there was no single host clone that was superior to all other clones in the resistance to every parasite isolate. Likewise, there was no parasite isolate that was superior to all other isolates in infectivity to every host clone. This form of host clone‐parasite isolate interaction indicates the potential for coevolution based on frequency‐dependent selection. Infection success of original host clone‐parasite isolate combinations (i.e., those combinations that were isolated together) was significantly higher than infection success of novel host clone‐parasite isolate combinations (i.e., those combinations that were created in the laboratory). This finding is consistent with the idea that parasites track specific host genotypes under natural conditions. In addition, correspondence analysis revealed that some host clones, although distinguishable with neutral genetic markers, were susceptible to the same set of parasite isolates and thus probably shared resistance genes.     

Galleria mellonella Infection Model Demonstrates High Lethality of ST69 and ST127 Uropathogenic E. coli

Galleria mellonella larvae are an alternative in vivo model for investigating bacterial pathogenicity. Here, we examined the pathogenicity of 71 isolates from five leading uropathogenic E. coli (UPEC) lineages using G. mellonella larvae. Larvae were challenged with a range of inoculum doses to determine the 50% lethal dose (LD₅₀) and for analysis of survival outcome using Kaplan-Meier plots. Virulence was correlated with carriage of a panel of 29 virulence factors (VF). Larvae inoculated with ST69 and ST127 isolates (10⁴ colony-forming units/larvae) showed significantly higher mortality rates than those infected with ST73, ST95 and ST131 isolates, killing 50% of the larvae within 24 hours. Interestingly, ST131 isolates were the least virulent. We observed that ST127 isolates are significantly associated with a higher VF-score than isolates of all other STs tested (P≤0.0001), including ST69 (P<0.02), but one ST127 isolate (strain EC18) was avirulent. Comparative genomic analyses with virulent ST127 strains revealed an IS1 mediated deletion in the O-antigen cluster in strain EC18, which is likely to explain the lack of virulence in the larvae infection model. Virulence in the larvae was not correlated with serotype or phylogenetic group. This study illustrates that G. mellonella are an excellent tool for investigation of the virulence of UPEC strains. The findings also support our suggestion that the incidence of ST127 strains should be monitored, as these isolates have not yet been widely reported, but they clearly have a pathogenic potential greater than that of more widely recognised clones, including ST73, ST95 or ST131.     

Cydia pomonella granulovirus Genotypes Overcome Virus Resistance in the Codling Moth and Improve Virus Efficiency by Selection against Resistant Hosts

Cydia pomonella granulovirus (CpGV) has been used for 15 years as a bioinsecticide in codling moth (Cydia pomonella) control. In 2004, some insect populations with low susceptibility to the virus were detected for the first time in southeast France. RGV, a laboratory colony of codling moths resistant to the CpGV-M isolate used in the field, was established with collection of resistant insects in the field followed by an introgression of the resistant trait into a susceptible colony (Sv). The resistance level (based on the 50% lethal concentrations [LC₅₀s]) of the RGV colony to the CpGV-M isolate, the active ingredient in all commercial virus formulations in Europe, appeared to be over 60,000-fold compared to the Sv colony. The efficiency of CpGV isolates from various other regions was tested on RGV. Among them, two isolates (I12 and NPP-R1) presented an increased pathogenicity on RGV. I12 had already been identified as effective against a resistant C. pomonella colony in Germany and was observed to partially overcome the resistance in the RGV colony. The recently identified isolate NPP-R1 showed an even higher pathogenicity on RGV than other isolates, with an LC₅₀ of 166 occlusion bodies (OBs)/μl, compared to 1.36 × 10⁶ OBs/μl for CpGV-M. Genetic characterization showed that NPP-R1 is a mixture of at least two genotypes, one of which is similar to CpGV-M. The 2016-r4 isolate obtained from four successive passages of NPP-R1 in RGV larvae had a sharply reduced proportion of the CpGV-M-like genotype and an increased pathogenicity against insects from the RGV colony.     

东北地区小麦赤霉病菌DNA随机扩增多态性分析*

利用RAPD对我国东北地区引致小麦赤霉病的2种镰刀菌进行种群分析,并与江苏和西北的菌株进行了比较。共筛选出16个引物用于扩增反应,其扩增图谱显示供试菌株在种间和种内均具多态性。多数引物扩增出了种的特征性谱带,可用作种的鉴定。综合所有谱带系统聚类所得树状图明显地将Fusarium graminearum的34个菌株和F.avenaceum的5个菌株各聚为一类,每一类又可区分为不同组,以前者分为3组,后者分为2组差异显著,表明种内存在不同的菌系类型;组的划分与菌株致病力及其寄主品种间没有必然的相关性,但与菌株分布的大区域生态气候类型似有联系,供试的东北地区F.graminearum大多数菌株与西北的菌系有较大的遗传相似性,与江苏的菌系相距甚远。     

First Report of Erwinia amylovora Fire Blight in Belarus

Erwinia amylovora is a phytopathogenic bacterium that causes fire blight, an economically important disease of Rosaceae . Several isolates from pears and apples with fire blight symptoms from Belarus were identified as E. amylovora . All tested isolates were yellow and mucoid on MM2Cu medium, positive in levan production and showed pathogenicity in immature pear fruits. These isolates have identical total protein patterns with E. amylovora 1/79. The PCR with specific primers for E. amylovora harpin gene also gave positive results.     

2003-2013年小麦品种(系)抗条锈性鉴定及评价

2003-2013年在甘肃省农业科学院植物保护研究所兰州温室和甘谷试验站,分别对来自国内35个相关育种单位的冬春小麦品种(系)5001份,其中冬小麦4291份、春小麦710份,进行苗期混合菌、成株期分小种和混合菌抗条锈性接种鉴定,结果表明:全生育期表现免疫近免疫的有兰天31号等479份,高抗的有兰天23号等76份,中抗的有天选49等291份,分别占9.58％、1.52％和5.82％;成株期表现免疫近免疫的有天选50号等840份,高抗的有兰天27号等47份,中抗的有天选52等311份,分别占16.80％、0.94％和6.22％;苗期表现免疫近免疫的有兰天30号等964份,高抗的有天98102等122份,中抗的有00-30等273份,分别占19.28％、2.44％和5.46％.冬小麦有天选49号等914份材料表现全生育期抗病,占18.28％;有97-473等906份成株期表现抗病,占18.12％;有兰天20号等1225份苗期表现抗病,占24.50％.春小麦有定西41号等113份材料全生育期表现抗病,占2.26％;有陇春28号等125份成株期表现抗病,占2.50％;有0109-1等114份苗期对混合菌表现抗病,占2.28％.先后在甘肃天水汪川良种场对相关材料进行成株期抗条锈性评价,结果发现:1154份从小种圃筛选出的抗病材料中,表现抗病的有兰天31号等745份,占64.56％;105份甘肃陇南生产品种中,到2013年表现抗病的仅有兰天28号、中梁31号等30份材料,占28.57％;后备品系中,00-30-2-1、CP04-20、00127-2-3等抗性表现优异;抗源材料中,仅有贵农775、中四、T.Spelta albun、贵协1、贵协3等少数材料表现抗病,重要抗源材料贵农21、贵农22、南农92R、川麦42、Moro从2011年开始在田间表现感病,逐步失去利用价值.其衍生系品种材料如陇鉴9343、天选43号、中梁29号、兰天17号、兰天24号等也在田间逐步感病,条锈病发生流行压力持续增大.     

Characterization of Bacillus altitudinis as a New Causative Agent of Bacterial Soft Rot

A total of 67 bacterial isolates were obtained from apple and pear fruits with signs of soft rot collected from Egyptian markets. Pathogenicity tests showed that 25 isolates (37%) were pathogenic to apple and pear fruits, with considerable variation of virulence. Among these isolates, 16 (64%) were Gram‐positive, motile, spore‐forming long rods and were identified as members of the genus Bacillus based on an API test. In addition, five isolates (20%) were Gram‐negative, non‐spore‐forming, motile, oxidase and catalase‐positive short rods and were identified as members of the genus Pseudomonas. Furthermore, four isolates (16%) were Gram‐negative, non‐spore‐forming, motile, catalase‐positive and oxidase negative short rods and were identified as belonging to the genus Erwinia. All selected isolates showed a wide host range and could cause soft rot of all representative fruits and vegetables tested. The three most virulent isolates, AB4, AB6 and PB6, exhibited the highest soft rot severity on different apple and pear cultivars, and apple cv. Anna (116) was the most susceptible to infection by isolates AB4 and AB6, with soft rot severities of 63.33 and 60.67%, respectively. Also, pear cv. Le‐Conte was most susceptible to infection by isolate AB6, with a soft rot severity of 89.9%. A phylogenetic tree based on 16S rRNA gene sequences indicated that strains AB4 and AB6 were very similar to one another and also showed a similarity of 99% to Bacillus altitudinis, and strain PB6 revealed a similarity of 99% to Bacillus pumilus. To our knowledge, this is the first report of B. altitudinis as a soft rot pathogen for both apple and pear fruits.