Flaccumfaciens Pv Research Articles

Atividade antimicrobiana de extrato fenólico de Lafoensia pacari contra ftopatógenos de feijoeiro

ABSTRACT Lafoensia pacari represents an alternative to control phytopathogens and common bean (Phaseolus vulgaris L.) diseases. This study aimed to investigate the chemical composition of L. pacari phenolics-containing extract obtained from leaves and assess its in vitro and in vivo inhibitory activity against Curtobacterium flaccumfaciens pv. flaccumfaciens, Xanthomonas axonopodis pv. phaseoli, Xanthomonas fuscans subsp. fuscans, Xanthomonas sp., Colletotrichum lindemuthianum, Fusarium oxysporum and Macrophomina phaseolina. The microbial susceptibility screening and the extract’s potential to reduce the anthracnose severity and the common bacterial blight were examined. Eleven phenolic compounds were identified, eight of which were described for the first time in L. pacari leaves: gentisic, caffeic, p-coumaric, protocatechuic and vanillic acids, luteolin, naringenin and quercetin. The L. pacari extract completely inhibited bacterial growth at the concentration of 0.62-1.25 %, as well as the mycelial growth of the C. lindemuthianum (BRM 007626) isolate at the concentration of 5 % (v/v). Under greenhouse conditions, the extract led to the control of the common bacterial blight caused by X. axonopodis pv. phaseoli (BRM 25302) in the Pérola bean cultivar and to a low efficiency in the control of anthracnose caused by C. lindemuthianum (BRM 007447) in the IPA 7419 cultivar.

Whole-Genome Data from Curtobacterium flaccumfaciens pv. flaccumfaciens Strains Associated with Tan Spot of Mungbean and Soybean Reveal Diverse Plasmid Profiles.

Despite the substantial economic impact of Curtobacterium flaccumfaciens pv. flaccumfaciens on legume production worldwide, the genetic basis of its pathogenicity and potential host association is poorly understood. The production of high-quality reference genome assemblies of C. flaccumfaciens pv. flaccumfaciens strains associated with different hosts sheds light on the genetic basis of its pathogenic variability and host association. Moreover, the study of recent outbreaks of bacterial wilt and microevolution of the pathogen in Australia requires access to high-quality reference genomes that are sufficiently closely related to the population being studied within Australia. We provide the first genome assemblies of C. flaccumfaciens pv. flaccumfaciens strains associated with mungbean and soybean, which revealed high variability in their plasmid composition. The analysis of C. flaccumfaciens pv. flaccumfaciens genomes revealed an extensive suite of carbohydrate-active enzymes potentially associated with pathogenicity, including four carbohydrate esterases, 50 glycoside hydrolases, 23 glycosyl transferases, and a polysaccharide lyase. We also identified 11 serine peptidases, three of which were located within a linear plasmid, pCff119. These high-quality assemblies and annotations will provide a foundation for population genomics studies of C. flaccumfaciens pv. flaccumfaciens in Australia and for answering fundamental questions regarding pathogenicity factors and adaptation of C. flaccumfaciens pv. flaccumfaciens to various hosts worldwide and, at a broader scale, contribute to unraveling genomic features of gram-positive, xylem-inhabiting bacterial pathogens.[Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Protocol for detecting Curtobacterium flaccumfaciens pv. flaccumfaciens in the leaves of infected bean plants (Phaseolus vulgaris L.)

Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff), which is a gram-positive bacterium that causes wilting in several cultivated plants, is one of the main disease-causing bacteria in beans (Phaseolus vulgaris L.). Different techniques are employed to detect pathogens in bean plants; however, only a few slow and inefficient methodologies can be used to detect Cff. Hence, there is a need for rapid and efficient techniques to detect Cff for disease management. The objective of our study was to develop a technique to effectively detect Cff in the leaves of infected bean plants by optimizing a previously developed method. We modified the extraction method by reducing the amount of water used, replacing seeds with leaf tissues (obtained from the veins and petioles) and using CffFOR2 and CffREV4 primers specific for Cff. Our optimized method exploits a concentration gradient generated in the plant tissue through osmosis to disrupt the plant cell wall and efficiently isolate bacterial cells. DNA extracted from the isolated bacterial cells was amplified by polymerase chain reaction. This method allowed efficient detection of Cff in leaf tissues.

Survival of Curtobacterium flaccumfaciens pv. flaccumfaciens in the phyllosphere and rhizosphere of crops

Knowledge of the ecological survival niches of Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff), the causal agent of bean bacterial wilt, is essential for the efficient disease management. Our study evaluated the survival of Cff in the phyllospheres and rhizospheres of barley, black oat, canola, common bean, forage turnip, maize, pearl millet, ryegrass, sorghum, soybean, sunflower, velvet bean, wheat and white oat planted in a greenhouse. The aerial parts of the plants were inoculated by spraying a bacterial suspension (107 CFU.mL−1) from the strain Feij. 2628A, which is resistant to rifampicin and pathogenic to common bean. The soil of the pots was infested with 200 mL of the same suspension. Cff survival was evaluated every seven days for 70 days, and the survival periods were confirmed by selecting strains from all samples and performing PCR with specific primers. Cff survived for at least seven days in the phyllosphere, and 21 days in the rhizosphere of all evaluated crops. Based on our results, barley, black oat, canola, forage turnip, maize, pearl millet, ryegrass, sorghum, soybean, sunflower, velvet bean, wheat and white oat can be potential asymptomatic hosts for Cff, and their cultivation in succession with common bean is not recommended in areas with a history of bacterial wilt occurrence.

Effect of crop rotation on common bean cultivars against bacterial wilt caused by Curtobacterium flaccumfaciens pv. flaccumfaciens

A crop rotation system can reduce phytopathogen inoculum, and consequently reduce the incidence and severity of disease. Bean bacterial wilt is an important disease and several crops can act as inoculum sources for Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff). The aim was to evaluate the influence of crop rotation systems on 10 common bean cultivars against bacterial wilt. Experiments were located in two different areas in Brazil (2012), cultivated under a no-tillage system and with a history of the disease. The evaluated rotation systems were black oat, wheat and fallow followed by common bean. After harvest, 10 dry bean cultivars were sown, together with a fallow area. Disease incidence and severity were assessed at 45, 60 and 80 days after sowing. Also evaluated were four agronomical parameters: pod numbers, grain numbers, total weight of grains per plant and weight of 100 grains. Epiphytic and endophytic colonization by Cff was evaluated in black oat and wheat, and in crop debris. The rotation systems significantly influenced the incidence and severity of bacterial wilt in common bean cultivars in both areas and negatively affected the four agronomic parameters. The cultivars BRS Campeiro, BRS Estilo, IPR Tuiuiu, IPR Tangara and IPR Campos Gerais presented low severity and incidence of the disease and higher productivity. Cff strains were recovered from black oat, wheat and crop debris. Our results reinforce the importance of planting non-Cff host crops in rotation systems with common bean, as well as planting cultivars with a level of resistance to bacterial wilt.

Occurrence of Curtobacterium flaccumfaciens pv. flaccumfaciens in the state of Paraná and its pathogenicity in beans

Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff) is a bacterial vascular pathogen that infects economically important crops, such as soybean and beans. Currently, this pathogen is widespread in the main bean-producing regions, causing great economic losses. Considering the environmental adaptability of this pathogen and its evolution over time, it is necessary to obtain new information and analyse its status. The objective of this study was to identify whether Cff occurs in the field by collecting plants from different regions in the state of Parana and determine its pathogenicity in bean plants. For Cff diagnosis, plants with wilt symptoms were obtained from commercial and experimental crops in the Campo do Tenente, Corbelia, Ivai, Santa Tereza do Oeste, and Senges municipalities. The samples were subjected to a bacteriological examination and isolation of the bacteria in specific culture medium. To confirm the species of the isolates obtained, specific primers for Cff were used in PCR. The isolates were inoculated into susceptible bean plants (BRS Supremo) to evaluate their pathogenicity. The experimental design adopted was a randomized block design with four replicates. The bacterium was found in all collection locations. Sixteen isolates were characterized as Cff by PCR. The isolates inoculated into the susceptible bean cultivar showed high levels of severity. The results show that Cff isolates in bean crops in bean-producing regions in Parana show a certain level of field adaptability.

Complete Genome Sequencing Provides Novel Insight Into the Virulence Repertories and Phylogenetic Position of Dry Beans Pathogen Curtobacterium flaccumfaciens pv. flaccumfaciens.

Bacterial wilt of dry beans (family Fabaceae) caused by the actinobacterial agent Curtobacterium flaccumfaciens pv. flaccumfaciens is one of the most important diseases threatening edible legume production around the globe. Despite the economic losses due to the bacterial wilt disease, the pathogen has not so far been investigated for its genomic features, pathogenicity determinants, and virulence strategies. Here we present the first complete genome sequence of a highly virulent bacteriocin-producing C. flaccumfaciens pv. flaccumfaciens strain P990. The bacterium has a circular chromosome consisting of 3,736 kbp with the G+C% content of 71.0%. Furthermore, a 147-kbp circular plasmid (pCff1) with 66.1% G+C% content as well as two circular plasmid-like DNAs with sizes of 25 and 22 kbp were detected within the genomic contents of C. flaccumfaciens pv. flaccumfaciens. Phylogenetic analyses revealed that only a few number of Curtobacterium sp. strains deposited in the public databases could be classified within the species C. flaccumfaciens. Comparative genomics of C. flaccumfaciens pv. flaccumfaciens using the genome sequences of actinobacterial plant pathogens revealed the presence of a set of unique low G+C% content genomic islands in the C. flaccumfaciens pv. flaccumfaciens genome. Homologs of pathogenicity-determinant loci capable of producing 1,4-beta-xylanase (xysA), pectate lyase (pelA1 and pelA2), serine protease (chpC, chpG, and pat-1), and sortase (srtA) were detected in C. flaccumfaciens pv. flaccumfaciens genome. The genomic data presented here extend our understanding of the C. flaccumfaciens pv. flaccumfaciens genomic features and pave the ways of research on functional and interaction genetics to combat the risk of bacterial wilt disease in the 21st century's dry bean industry.

A Powerful LAMP Weapon against the Threat of the Quarantine Plant Pathogen Curtobacterium flaccumfaciens pv. flaccumfaciens.

Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff) is a Gram-positive phytopathogenic bacterium attacking leguminous crops and causing systemic diseases such as the bacterial wilt of beans and bacterial spot of soybeans. Since the early 20th century, Cff is reported to be present in North America, where it still causes high economic losses. Currently, Cff is an emerging plant pathogen, rapidly spreading worldwide and occurring in many bean-producing countries. Infected seeds are the main dissemination pathway for Cff, both over short and long distances. Cff remains viable in the seeds for long times, even in field conditions. According to the most recent EU legislation, Cff is included among the quarantine pests not known to occur in the Union territory, and for which the phytosanitary inspection consists mainly of the visual examination of imported bean seeds. The seedborne nature of Cff combined with the globalization of trades urgently call for the implementation of a highly specific diagnostic test for Cff, to be routinely and easily used at the official ports of entry and into the fields. This paper reports the development of a LAMP (Loop-Mediated Isothermal Amplification) specific for Cff, that allows the detection of Cff in infected seeds, both by fluorescence and visual monitoring, after 30 min of reaction and with a detection limit at around 4 fg/μL of pure Cff genomic DNA.

Complete Genome Sequence Resource of a Strain of Curtobacterium flaccumfaciens pv. flaccumfaciens, the Causal Agent of Bacterial Wilt of Common Bean, from Turkey.

Curtobacterium flaccumfaciens pv. flaccumfaciens is the causal agent of bacterial wilt of common bean (Phaseolus vulgaris), a disease that can reduce yields of this economically important crop worldwide. Current genomics resources for this bacterial pathogen are limited. Therefore, long-read sequencing was used to determine the complete genome sequence of a pathogenic C. flaccumfaciens pv. flaccumfaciens strain isolated from common bean leaves showing irregular necrotic lesions with yellow borders collected in a commercial field in Turkey in 2015.

Survival of Curtobacterium flaccumfaciens pv. flaccumfaciens in weeds

AbstractWeeds are important alternative hosts of pathogens, responsible for the survival and spread of phytopathogenic bacteria. Our study evaluated the potential of weeds as hosts of Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff), causal agent of bacterial wilt, one of the main diseases of common beans. Cff survival was evaluated in the phyllosphere and in the rhizosphere of 21 weeds, in four experiments under field conditions, during the years 2018 and 2019. The aerial part of the plant was inoculated by spraying bacterial suspension (107 cfu/ml) of Cff, while the soil of the growing pots was infested with the same suspension. Cff survival was evaluated every 7 days, for 70 days. The identity of the bacterium was confirmed by PCR with the specific primers CffFOR2 and CffREV4, from strains recovered from all samples. Principal component analysis (PCA) showed that high temperatures and rainfall reduced Cff survival in the phyllosphere, while high temperatures reduced the survival of the bacterium in the rhizosphere. Our results demonstrated that Amaranthus viridis (family Amaranthaceae), Conyza bonariensis, Emilia fosbergii, Galinsoga parviflora, Gnaphalium purpureum (Asteraceae), Raphanus sativus, Lepidium virginicum (Brassicaceae), Commelina benghalensis (Commelinaceae), Ipomoea triloba (Convolvulaceae), Cyperus rotundus (Cyperaceae), Senna obtusifolia (Fabaceae), Digitaria insularis (Poaceae), Nicandra physalodes, and Solanum americanum (Solanaceae) are potential hosts for Cff. Their eradication in common bean fields is recommended, especially in fields with a history of bacterial wilt occurrence.

Bacterial wilt of dry beans caused by Curtobacterium flaccumfaciens pv. flaccumfaciens: A new threat from an old enemy.

Bacterial wilt and tan spot of dry beans (family Fabaceae), caused by Curtobacterium flaccumfaciens pv. flaccumfaciens, is an important emerging disease threatening the edible legume industry around the globe. The management of bacterial wilt has been a major problem since its original description in 1922. This is in part due to the seedborne nature of the pathogen allowing the bacterium to be transmitted long distances via infected seeds, as well as a lack of detailed molecular information concerning the pathogenicity repertoires and virulence determinates of the pathogen. Identification can also be difficult owing to the presence of five different colony colour variants (i.e., yellow, orange, pink, purple, and red) on culture media. In this review, we provide an overview of the aetiology, epidemiology, and management strategies of bacterial wilt disease. First, a comprehensive and comparative symptomology of the disease on different dry bean species is described. Then, the taxonomic history of the causal agent and utility of high‐throughput sequencing‐based approaches in the precise characterization of the pathogen is explained. Furthermore, we provide an updated outline on the global distribution of the pathogen, highlighting expansion of the causal agent into the areas with no history of the disease until the beginning of the current century. Finally, because there are limited options for use of conventional pesticides against the pathogen, we highlight the use of integrated pest management strategies, for example quarantine inspections, resistant cultivars, and crop sanitation, to combat the risk of bacterial wilt disease in the dry bean industry.Disease symptomsInterveinal chlorosis on leaflets leading to necrotic areas and systemic wilt. Seed discolouration to yellow, orange, pink, or purple is seen in white‐seeded cultivars.Host rangeCauses bacterial wilt and tan spot disease on edible dry beans in the Fabaceae family, including common bean (Phaseolus vulgaris), cowpea (Vigna unguiculata), mungbean (Vigna radiata), soybean (Glycine max), as well as a number of weed species.Taxonomic status of the pathogenBacteria; phylum Actinobacteria; order Actinomycetales; suborder: Micrococcineae; family Microbacteriaceae; genus Curtobacterium; species Curtobacterium flaccumfaciens. Synonyms Corynebacterium flaccumfaciens subsp. flaccumfaciens; Corynebacterium flaccumfaciens pv. flaccumfaciens, Corynebacterium flaccumfaciens, Phytomonas flaccumfaciens, Bacterium flaccumfaciens. Microbiological propertiesMulticoloured (yellow, orange, pink, purple, and red), gram‐positive, aerobic, curved rod, nonspore‐forming, polar flagellated, motile cells.DistributionWidespread in America (Brazil, Canada, and the USA), Australia, and Iran. Restricted occurrence in Africa and Europe.Phytosanitary categorizationEPPO A2 list no. 48, EU Annex II⁄B.

Phenotypic and Molecular-Phylogenetic Analysis Provide Novel Insights into the Diversity of Curtobacterium flaccumfaciens.

A multiphasic approach was used to decipher the phenotypic features, genetic diversity, and phylogenetic position of 46 Curtobacterium spp. strains isolated from dry beans and other annual crops in Iran and Spain. Pathogenicity tests, resistance to arsenic compounds, plasmid profiling and BOX-PCR were performed on the strains. Multilocus sequence analysis (MLSA) was also performed on five housekeeping genes (i.e., atpD, gyrB, ppk, recA, and rpoB) of all the strains, as well as five pathotype strains of the species. Pathogenicity test showed that six out of 42 strains isolated in Iran were nonpathogenic on common bean. Despite no differences found between pathogenic and nonpathogenic strains in their plasmid profiling, the former were resistant to different concentrations of arsenic, while the latter were sensitive to the same concentrations. Strains pathogenic on common bean were polyphyletic with at least two evolutionary lineages (i.e., yellow-pigmented strains versus red/orange-pigmented strains). Nonpathogenic strains isolated from solanaceous vegetables were clustered within either the strains of C. flaccumfaciens pv. flaccumfaciens or different pathovars of the species. The results of MLSA and BOX-PCR analysis were similar to each other and both methods were able to discriminate the yellow-pigmented strains from the red/orange-pigmented strains. A comprehensive study of a worldwide collection representing all five pathovars as well as nonpathogenic strains of C. flaccumfaciens is warranted for a better understanding of the diversity within this phytopathogenic bacterium.

Plant-to-seed transmission of Curtobacterium flaccumfaciens pv. flaccumfaciens on soybean

Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff) causes bacterial tan spot on soybeans (Glycine max), which was detected in Brazilian crops in 2012. The objective of this study was to determine the Cff transmission rate from plant to seeds in soybean cultivars with different levels of resistance to bacterial tan spot. For this, two assays were conducted under greenhouse and laboratory conditions. Inoculation in soybean plants was performed by the stem puncture method in the first assay and the toothpick method in the second assay. The Cff transmission to seed was checked by plating the suspensions extracted from seeds of the inoculated plants on semi-selective medium. Molecular identification of Cff amongst the obtained isolates was performed by PCR. The susceptible cultivars, BRS 284 and NS 5858 RR, showed zero to 1% Cff seed transmission, while the moderately resistant cultivar, BRS 388RR, showed 0% seed transmission. We concluded that Cff can be transmitted to soybean seeds of susceptible cultivars at low rates.

Pest categorisation of Curtobacterium flaccumfaciens pv. flaccumfaciens.

Following a request from the European Commission, the EFSA Panel on Plant Health performed a pest categorisation of the seed‐borne bacterium Curtobacterium flaccumfaciens pv. flaccumfaciens. The pest is regulated in Council Directive 2000/29/EC (Annex IIB) as a harmful organism whose introduction into, and spread within, the protected zones (PZ) of Greece, Portugal and Spain shall be banned if present on seeds of Phaseolus vulgaris and of Dolichos. The bacterium is widely distributed outside the EU and causes a systemic vascular disease (bacterial wilt of bean) as well as bacterial tan spot disease on soybean. The pest was sporadically recorded in several EU Member States in the past, but is currently not known to occur in the EU. The identity of the bacterium is well established and identification methods are available. The major host is common bean (Phaseolus vulgaris), but other crops and weeds are, or may be, hosts or play a role as reservoirs, with uncertainties. Seed transmission remains uncertain for minor and alternative host species. The main pathway for entry is seed. The role of other pathways (e.g. irrigation water and infected residues) is uncertain. Should the bacterium enter the EU (including the PZ), it may establish, spread and have an impact on its host crops. The use of healthy seeds is the most effective control measure. Curtobacterium flaccumfaciens pv. flaccumfaciens fits all the criteria assessed by EFSA to be regarded as a Union quarantine pest.

Epiphytic Curtobacterium flaccumfaciens strains isolated from symptomless solanaceous vegetables are pathogenic on leguminous but not on solanaceous plants

In Iran, during 2013–16, 16 Gram‐positive corynebacteria‐like strains were recovered from the epiphytic parts of solanaceous vegetables including eggplant, pepper and tomato. The strains were recovered accidentally as a result of monitoring for other bacterial pathogens in solanaceous fields. The strains were phenotypically different from Clavibacter michiganensis strains. Although none of the strains were pathogenic on their host of isolation or on any other solanaceous plants, 12 out of 16 strains were pathogenic on common bean, cowpea, mung bean and soybean. Colonization by strains was observed on maize, zucchini, faba bean, honeydew melon, rapeseed, sugar beet and sunflower plants under greenhouse conditions. In PCR tests, the primer pair CffFOR2/CffREV4, specific for Curtobacterium flaccumfaciens pv. flaccumfaciens, enabled the amplification of the appropriately sized fragment in 12 out of 16 strains, and all 12 strains were pathogenic on dry beans. Phylogenetic analysis, using the gyrB and recA genes, showed all 16 bacterial strains clustered within several pathovars of C. flaccumfaciens. A nonpathogenic yellow‐pigmented strain (Xeu15) was clustered with the type strains of C. flaccumfaciens pv. betae and C. flaccumfaciens pv. oortii. Bacteriocin profiling assays revealed no significant differences among the pathogenic and nonpathogenic strains. Host range and population dynamics of four representative strains on 17 plant species showed population build‐up of the strains only on common bean, cowpea, wheat and red nightshade plants. The results provide important insights into the possible role of nonhost plants as reservoirs of plant pathogenic bacteria, which has important implications in plant disease epidemiology and management.

Reaction of common bean lines to Xanthomonas axonopodis pv. phaseoli and Curtobacterium flaccumfaciens pv. Flaccumfaciens

Abstract The aim of this study was to evaluate the resistance of 58 common bean lines against common bacterial blight (Xanthomonas axonopodis pv. phaseoli) and bacterial wilt (Curtobacterium flaccumfaciens pv. flaccumfaciens). The experimental design consisted of completely randomized blocks, with four replications per pathogen. The results were subjected to variance analysis by the F test at 1% probability. Significant differences between the treatments indicated different resistance levels among the lines against both pathogens. According to the Scott-Knott test, six lines were resistant to Xanthomonas axonopodis pv. phaseoli, 14 moderately resistant, and 38 susceptible. To Curtobacterium flaccumfaciens pv. flaccumfaciens, 11 lines were resistant, 26 moderately resistant and 21 susceptible. Among these, the lines Pr10-3-4/1, Pr10-5-2/1 and Pr10-5-2/2 of the black bean group and C10-2-4/2 of the Carioca group were resistant to both major bacterial diseases affecting common bean in Brazil.

Normes OEPP

Normes <scp>OEPP</scp>

Evaluation of seedborne bacterial pathogens on common bean cultivars grown in central Anatolia region, Turkey

Bacterial diseases of bean cause economically important losses worldwide. The most important method for managing bacterial diseases on bean is the use of pathogen-free seed. In this study, 198 different dry bean seed samples of six different cultivars including Dermason, Cali, Sira, Battal, Bombay and Seker, were collected from 12 provinces of Central Anatolia Region of Turkey. All were tested to investigate the seedlots as primary inoculum sources of the major bacterial diseases. The data revealed that 22,72 %, 13,63 %, 11,11 %, 1,51 % and 0.5 % of seed samples tested were contaminated with five seedborne bacterial pathogens, Pseudomonas savastanoi pv. phaseolicola (Psp), Pseudomonas syringae pv. syringae (Pss), Xanthomonas axonopodis pv. phaseoli (Xap), X. axonopodis pv. phaseoli var. fuscans (Xapf) and Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff), respectively. All bacterial strains isolated were identified based on morphological, physiological, biochemical, molecular and pathogenicity tests. The results showed that Psp and Pss were found together on cv. Cali; Psp and Xap on cv. Dermason and cv. Sira; and Pss and Xap on cv. Seker, cv. Dermason, and cv. Cali. Therefore, the results in the present study suggested that evaluation and selection of pathogen-free seeds are very important for preventing the spread of pathogens and effective management of seed borne bacterial diseases prevalent in bean growing regions; in addition to implementation of integrated crop production strategies such as crop rotation, sanitation, seed treatment, tolerant/resistant cultivar selection and proper bactericide application.

Normes OEPP EPPO Standards

Normes OEPP EPPO Standards

Differential interactions between Curtobacterium flaccumfaciens pv. flaccumfaciens and common bean.

Bacterial wilt of common bean caused by Curtobacterium flaccumfaciens pv. flaccumfaciens is an important disease in terms of economic importance. It reduces grain yield by colonizing xylem vessels, subsequently impeding the translocation of water and nutrients to the superior plant parts. The existence of physiological races in C. flaccumfaciens pv. flaccumfaciens has not so far been reported. The objective of the present investigation was to identify physiological races, evaluate differential interaction, and select resistant genotypes of common bean. Initially, 30 genotypes of common bean were inoculated with eight isolates exhibiting different levels of aggressiveness, under controlled greenhouse conditions. Disease was assessed 15 days after inoculation. The existence of differential interactions between C. flaccumfaciens pv. flaccumfaciens isolates and common bean genotypes were identified by utilizing partial diallel analysis. The most aggressive isolates were BRM 14939 and BRM 14942 and the least aggressive isolates were BRM 14941 and BRM 14946. The genotypes IPA 9, Ouro Branco, and Michelite were selected as more resistant among the test isolates. The genotypes IAC Carioca Akytã, BRS Notável, Pérola, IAC Carioca Aruã, and Coquinho contributed more to the isolate x genotype interaction according to the ecovalence method of estimation, and were, therefore, indicated as differentials. Based on these results, it was possible to conclude that physiological races of the pathogen exist, to select resistant genotypes, and to propose a set of differentials.