RESUMO

Bacterial spot is a serious disease caused by several species of Xanthomonas affecting pepper and tomato production worldwide. Since the strategies employed for disease management have been inefficient and pose a threat for environmental and human health, the development of alternative methods is gaining relevance. The aim of this study is to isolate and characterize lytic phages against Xanthomonas pathogens. Here, we isolate two jumbo phages, named XaC1 and XbC2, from water obtained from agricultural irrigation channels by the enrichment technique using X. vesicatoria as a host. We determined that both phages were specific for inducing the lysis of X. vesicatoria strains, but not of other xanthomonads. The XaC1 and XbC2 phages showed a myovirus morphology and were classified as jumbo phages due to their genomes being larger than 200 kb. Phylogenetic and comparative analysis suggests that XaC1 and XbC2 represent both different and novel genera of phages, where XaC1 possesses a low similarity to other phage genomes reported before. Finally, XaC1 and XbC2 exhibited thermal stability up to 45 °C and pH stability from 5 to 9. All these results indicate that the isolated phages are promising candidates for the development of formulations against bacterial spot, although further characterization is required.

RESUMO

As agricultural practices become more sustainable, adopting more sustainable practices will become even more relevant. Searching for alternatives to chemical compounds has been the focus of numerous studies, and bacteriocins are tools with intrinsic biotechnological potential for controlling plant diseases. We continued to explore the biotechnological activity of the bacteriocin Gluconacin from Gluconacetobacter diazotrophicus, PAL5 strain, by investigating this protein's antagonism against important tomato phytopathogens and demonstrating its effectiveness in reducing bacterial spots caused by Xanthomonas perforans. In addition to this pathogen, the bacteriocin Gluconacin demonstrated bactericidal activity in vitro against Ralstonia solanacearum and Pseudomonas syringae pv. tomato, agents that cause bacterial wilt and bacterial spots, respectively. Bacterial spot control tests showed that Gluconacin reduced disease severity by more than 66%, highlighting the biotechnological value of this peptide in ecologically correct formulations.

RESUMO

Xanthomonas vesicatoria is one of the causal agents of bacterial spot, a disease that seriously affects the production of tomato (Solanum lycopersicum) and pepper (Capsicum annum) worldwide. In Argentina, bacterial spot is found in all tomato producing areas, with X. vesicatoria being one of the main species detected in the fields. Previously, we isolated three X. vesicatoria strains BNM 208, BNM 214, and BNM 216 from tomato plants with bacterial spot, and found they differed in their ability to form biofilm and in their degree of aggressiveness. Here, the likely causes of those differences were explored through genotypic and phenotypic studies. The genomes of the three strains were sequenced and assembled, and then compared with each other and also with 12 other publicly available X. vesicatoria genomes. Phenotypic characteristics (mainly linked to biofilm formation and virulence) were studied in vitro. Our results show that the differences observed earlier between BNM 208, BNM 214, and BNM 216 may be related to the structural characteristics of the xanthan gum produced by each strain, their repertoire of type III effectors (T3Es), the presence of certain genes associated with c-di-GMP metabolism and type IV pili (T4P). These findings on the pathogenicity mechanisms of X. vesicatoria could be useful for developing bacterial spot control strategies aimed at interfering with the infection processes.

RESUMO

Yield and longevity of yellow passion fruit have been reduced by diseases such as the bacterial spot caused by Xanthomonas axonopodis pv. passiflorae. Genetic resistance has been confirmed as the most efficient and economical correct option to minimize this disease problem. Aiming at it, the objective of this research was to evaluate the incidence, severity and progression of the disease in 12 genotypes of sour passion fruit, in seedling stage in nursery greenhouse after inoculation of Xanthomonas axonopodis pv. passiflorae. The inoculation was performed with an isolate collected in the Pipiripau Rural Nucleus, Brasilia-DF, named UnB-1397 (1x106 CFU/mL), through induction of injuries. There were performed four assessments, with interval of 7 days except the first which was performed 11 days after inoculation. The incidence was estimated by the percentage of plants affected. To evaluate the severity, it was used the diagrammatic scale validated by Costa et al. (2018), with adaptations, using the measurement of the affected area by necrotic lesions on the leaf. All genotypes were susceptible to bacteriosis, 5 being considered moderately susceptible: F1BRS Pérola do Cerrado x Rosa Intenso, Mar20#21, Mar20#15b, Mar20#24xMar20#40 and FB200PL4R2 x Mar20#2005, with a mean of severity ranging from 11 to 25% of injured area in leaves.

A produtividade e a longevidade dos pomares de maracujazeiro-azedo têm sido comprometidas em razão de doenças como a bacteriose, causada por Xanthomonas axonopodis pv. passiflorae. A resistência genética tem se confirmado como a opção mais eficiente e econômica para minimizar tal problema. Dessa forma, o objetivo deste trabalho foi avaliar a reação de 12 genótipos de maracujazeiro, em fase de mudas, sob cultivo protegido, à Xanthomonas axonopodis pv. passiflorae. A inoculação com isolado denominado UnB-1397 (1x106 CFU/mL),coletado no Núcleo Rural de Pipiripau, Brasília-DF, se deu pela indução de ferimentos. Foram realizadas 4 avaliações, com intervalo de 7 dias, sendo a primeira avaliação realizada 11 dias após a inoculação. A incidência foi estimada pela porcentagem de plantas afetadas. Para avaliação da severidade, foi utilizada escala diagramática validada por Costa et al. (2018), com adaptações, utilizando-se a mensuração da área foliar atingida por lesões nas folhas. Todos os genótipos se mostraram suscetíveis à bacteriose, sendo 5 considerados moderadamente suscetíveis: F1 BRS Pérola do Cerrado x Rosa Intenso, Mar20#21, Mar20#15b, Mar20#24 x Mar20#40 e FB200PL4R2 x Mar20#2005, apresentando uma média de severidade que variou de 11 a 25% de área ou tecidos foliares lesionados.

Assuntos

RESUMO

Bacterial spot is an important disease of pepper in Bulgaria and Macedonia. For characterization of Xanthomonas species associated with bacterial spot, 161 strains were collected from various field pepper-growing regions. Among them, 131 strains were identified as Xanthomonas euvesicatoria and 30 as Xanthomonas vesicatoria using species-specific primers and polymerase chain reaction followed by restriction fragment length polymorphism analysis. To assess the genetic diversity of the strains, two methods (Random Amplified Polymorphic DNA and Repetitive Element Palindromic-Polymerase Chain Reaction) were applied. Discriminatory index was calculated and analysis of molecular variance was carried out. Combined random amplified polymorphic DNA analysis of the X. euvesicatoria strains with primers CUGEA-4 and CUGEA-6 had greater discriminative power (0.60) than repetitive element palindromic-polymerase chain reaction with ERIC and BOX A1R primers, which makes this method applicable for strain diversity evaluation. Discrimination among the X. vesicatoria strains was achieved by the use of ERIC primers and only for the Bulgarian strains. The results demonstrated that X. euvesicatoria was more diverse than X. vesicatoria and heterogeneity was observed mainly in the Bulgarian populations. According to the analysis of molecular variance, genetic variations in X. euvesicatoria were observed among and within populations from different regions, while the differences between the two countries were minor. Following the principal coordinates analysis, a relation between the climatic conditions of the regions and a genetic distance of the populations may be suggested.

Assuntos

RESUMO

ABSTRACT Bacterial spot is an important disease of pepper in Bulgaria and Macedonia. For characterization of Xanthomonas species associated with bacterial spot, 161 strains were collected from various field pepper-growing regions. Among them, 131 strains were identified as Xanthomonas euvesicatoria and 30 as Xanthomonas vesicatoria using species-specific primers and polymerase chain reaction followed by restriction fragment length polymorphism analysis. To assess the genetic diversity of the strains, two methods (Random Amplified Polymorphic DNA and Repetitive Element Palindromic-Polymerase Chain Reaction) were applied. Discriminatory index was calculated and analysis of molecular variance was carried out.Combined random amplified polymorphic DNA analysis of the X. euvesicatoria strains with primers CUGEA-4 and CUGEA-6 had greater discriminative power (0.60) than repetitive element palindromic-polymerase chain reaction with ERIC and BOX A1R primers, which makes this method applicable for strain diversity evaluation. Discrimination among the X. vesicatoria strains was achieved by the use of ERIC primers and only for the Bulgarian strains. The results demonstrated that X. euvesicatoria was more diverse than X. vesicatoria and heterogeneity was observed mainly in the Bulgarian populations. According to the analysis of molecular variance, genetic variations in X. euvesicatoria were observed among and within populations from different regions, while the differences between the two countries were minor. Following the principal coordinates analysis, a relation between the climatic conditions of the regions and a genetic distance of the populations may be suggested.

Assuntos

RESUMO

ABSTRACT Bacterial spot is an important disease of pepper in Bulgaria and Macedonia. For characterization of Xanthomonas species associated with bacterial spot, 161 strains were collected from various field pepper-growing regions. Among them, 131 strains were identified as Xanthomonas euvesicatoria and 30 as Xanthomonas vesicatoria using species-specific primers and polymerase chain reaction followed by restriction fragment length polymorphism analysis. To assess the genetic diversity of the strains, two methods (Random Amplified Polymorphic DNA and Repetitive Element Palindromic-Polymerase Chain Reaction) were applied. Discriminatory index was calculated and analysis of molecular variance was carried out.Combined random amplified polymorphic DNA analysis of the X. euvesicatoria strains with primers CUGEA-4 and CUGEA-6 had greater discriminative power (0.60) than repetitive element palindromic-polymerase chain reaction with ERIC and BOX A1R primers, which makes this method applicable for strain diversity evaluation. Discrimination among the X. vesicatoria strains was achieved by the use of ERIC primers and only for the Bulgarian strains. The results demonstrated that X. euvesicatoria was more diverse than X. vesicatoria and heterogeneity was observed mainly in the Bulgarian populations. According to the analysis of molecular variance, genetic variations in X. euvesicatoria were observed among and within populations from different regions, while the differences between the two countries were minor. Following the principal coordinates analysis, a relation between the climatic conditions of the regions and a genetic distance of the populations may be suggested.

RESUMO

Bacterial spot is an important disease of pepper in Bulgaria and Macedonia. For characterization of Xanthomonas species associated with bacterial spot, 161 strains were collected from various field pepper-growing regions. Among them, 131 strains were identified as Xanthomonas euvesicatoria and 30 as Xanthomonas vesicatoria using species-specific primers and polymerase chain reaction followed by restriction fragment length polymorphism analysis. To assess the genetic diversity of the strains, two methods (Random Amplified Polymorphic DNA and Repetitive Element Palindromic-Polymerase Chain Reaction) were applied. Discriminatory index was calculated and analysis of molecular variance was carried out.Combined random amplified polymorphic DNA analysis of the X. euvesicatoria strains with primers CUGEA-4 and CUGEA-6 had greater discriminative power (0.60) than repetitive element palindromic-polymerase chain reaction with ERIC and BOX A1R primers, which makes this method applicable for strain diversity evaluation. Discrimination among the X. vesicatoria strains was achieved by the use of ERIC primers and only for the Bulgarian strains. The results demonstrated that X. euvesicatoria was more diverse than X. vesicatoria and heterogeneity was observed mainly in the Bulgarian populations. According to the analysis of molecular variance, genetic variations in X. euvesicatoria were observed among and within populations from different regions, while the differences between the two countries were minor. Following the principal coordinates analysis, a relation between the climatic conditions of the regions and a genetic distance of the populations may be suggested.(AU)

RESUMO

Screening passion fruit genotypes to target resistance to scab and bacterial blight may play an important role in reducing the application of chemical products and decreasing losses caused by these diseases. It is likely that resistant genotypes can be found in ongoing breeding programs targeting production traits. Thus, the objective of this work was to evaluate the host status of eighteen passion fruit genotypes from the Breeding Program of the Universidade Federal de Viçosa (CRP 01-12 to CRP 16-12, CRP 19-12 and CRP 20-12) and two cultivars (FB 200 Yellow Master and FB 300 Araguari) of yellow passion fruit to scab (Cladosporium herbarum) and bacterial blight (Xanthomonas axonopodis pv. passiflorae). The fungus and the bacterium were artificially inoculated on wounded leaves at concentrations of 1 x 106 spores mL-1 and 1 x 108 cfu mL-1. Scab incidence and severity were assessed at 7, 14, 21, and 31 days after inoculation (DAI); whereas bacterial blight evaluations were performed at 10, 20, 28, and 44 DAI. The genotypes CRP 01-12 to CRP 16-12 and CRP 19-12 are moderately resistant to scab. All genotypes are highly susceptible to bacterial blight.(AU)

A seleção de genótipos de maracujazeiro visando resistência à verrugose e bacteriose pode ter importante papel na redução da aplicação de produtos químicos e perdas causadas por essas doenças. É provável que genótipos resistentes possam ser encontrados em programas de melhoramento visando seleção de caracteres relacionados à produção. Assim, o objetivo deste trabalho foi avaliar a hospedabilidade de dezoito genótipos de maracujazeiro-azedo provenientes do Programa de Melhoramento Genético da Universidade Federal de Viçosa (CRP 01-12 a CRP 16-12, CRP 19-12 e CRP 20-12) e dois cultivares comerciais (FB 200 Yellow Master e FB 300 Araguari) à verrugose (causada por Cladosporium herbarum) e bacteriose (Xanthomonas axonopodis pv. passiflorae). O fungo e a bactéria foram inoculados em folhas com ferimentos nas concentrações de 1 x 106 esporos mL-1 e 1 x 108 ufc mL-1. A incidência e a severidade de verrugose foram avaliadas aos 7, 14, 21 e 31 dias após a inoculação (DAI); enquanto que as avaliações da bacteriose foram aos 10, 20, 28 e 44 DAI. Os genótipos CRP 01-12 a CRP 16-12 e CRP 19-12 são moderamente resistentes à verrugose. Todos os genótipos são altamente suscetíveis à bacteriose.(AU)

Assuntos

RESUMO

Screening passion fruit genotypes to target resistance to scab and bacterial blight may play an important role in reducing the application of chemical products and decreasing losses caused by these diseases. It is likely that resistant genotypes can be found in ongoing breeding programs targeting production traits. Thus, the objective of this work was to evaluate the host status of eighteen passion fruit genotypes from the Breeding Program of the Universidade Federal de Viçosa (CRP 01-12 to CRP 16-12, CRP 19-12 and CRP 20-12) and two cultivars (FB 200 Yellow Master and FB 300 Araguari) of yellow passion fruit to scab (Cladosporium herbarum) and bacterial blight (Xanthomonas axonopodis pv. passiflorae). The fungus and the bacterium were artificially inoculated on wounded leaves at concentrations of 1 x 106 spores mL-1 and 1 x 108 cfu mL-1. Scab incidence and severity were assessed at 7, 14, 21, and 31 days after inoculation (DAI); whereas bacterial blight evaluations were performed at 10, 20, 28, and 44 DAI. The genotypes CRP 01-12 to CRP 16-12 and CRP 19-12 are moderately resistant to scab. All genotypes are highly susceptible to bacterial blight.

A seleção de genótipos de maracujazeiro visando resistência à verrugose e bacteriose pode ter importante papel na redução da aplicação de produtos químicos e perdas causadas por essas doenças. É provável que genótipos resistentes possam ser encontrados em programas de melhoramento visando seleção de caracteres relacionados à produção. Assim, o objetivo deste trabalho foi avaliar a hospedabilidade de dezoito genótipos de maracujazeiro-azedo provenientes do Programa de Melhoramento Genético da Universidade Federal de Viçosa (CRP 01-12 a CRP 16-12, CRP 19-12 e CRP 20-12) e dois cultivares comerciais (FB 200 Yellow Master e FB 300 Araguari) à verrugose (causada por Cladosporium herbarum) e bacteriose (Xanthomonas axonopodis pv. passiflorae). O fungo e a bactéria foram inoculados em folhas com ferimentos nas concentrações de 1 x 106 esporos mL-1 e 1 x 108 ufc mL-1. A incidência e a severidade de verrugose foram avaliadas aos 7, 14, 21 e 31 dias após a inoculação (DAI); enquanto que as avaliações da bacteriose foram aos 10, 20, 28 e 44 DAI. Os genótipos CRP 01-12 a CRP 16-12 e CRP 19-12 são moderamente resistentes à verrugose. Todos os genótipos são altamente suscetíveis à bacteriose.

Assuntos

RESUMO

The bacterial spot of tomato, caused by Xanthomonas spp., is a very important disease, especially in the hot and humid periods of the year. The chemical control of the disease has not been very effective for a number of reasons. This study aimed to evaluate, under greenhouse conditions, the efficacy of leaf-spraying chemicals (acibenzolar-S-methyl (ASM) (0.025 g.L(-1)), fluazinam (0.25 g.L(-1)), pyraclostrobin (0.08 g.L(-1)), pyraclostrobin + methiran (0.02 g.L(-1) + 2.2 g.L(-1)), copper oxychloride (1.50 g.L(-1)), mancozeb + copper oxychloride (0.88 g.L(-1) + 0.60 g.L(-1)), and oxytetracycline (0.40 g.L(-1))) on control of bacterial spot. Tomatoes Santa Clara and Gisele cultivars were pulverized 3 days before inoculation with Xanthomonas perforans. The production of enzymes associated with resistance induction (peroxidase, polyphenol oxidase, phenylalanine ammonia-lyase, ß-1,3-glucanase, and protease) was quantified from leaf samples collected 24 hours before and 24 hours after chemical spraying and at 1, 2, 4, 6, and 8 days after bacterial inoculation. All products tested controlled bacterial spot, but only ASM, pyraclostrobin, and pyraclostrobin + metiram increased the production of peroxidase in the leaves of the two tomato cultivars, and increased the production of polyphenol oxidase and ß-1,3-glucanase in the Santa Clara cultivar.

Assuntos

RESUMO

The bacterial spot of tomato, caused by Xanthomonas spp., is a very important disease, especially in the hot and humid periods of the year. The chemical control of the disease has not been very effective for a number of reasons. This study aimed to evaluate, under greenhouse conditions, the efficacy of leaf-spraying chemicals (acibenzolar-S-methyl (ASM) (0.025 g.L⁻¹), fluazinam (0.25 g.L⁻¹), pyraclostrobin (0.08 g.L⁻¹), pyraclostrobin + methiran (0.02 g.L⁻¹ + 2.2 g.L⁻¹), copper oxychloride (1.50 g.L⁻¹), mancozeb + copper oxychloride (0.88 g.L⁻¹ + 0.60 g.L⁻¹), and oxytetracycline (0.40 g.L⁻¹)) on control of bacterial spot. Tomatoes Santa Clara and Gisele cultivars were pulverized 3 days before inoculation with Xanthomonas perforans. The production of enzymes associated with resistance induction (peroxidase, polyphenol oxidase, phenylalanine ammonia-lyase, β-1,3-glucanase, and protease) was quantified from leaf samples collected 24 hours before and 24 hours after chemical spraying and at 1, 2, 4, 6, and 8 days after bacterial inoculation. All products tested controlled bacterial spot, but only ASM, pyraclostrobin, and pyraclostrobin + metiram increased the production of peroxidase in the leaves of the two tomato cultivars, and increased the production of polyphenol oxidase and β-1,3-glucanase in the Santa Clara cultivar.

Assuntos

RESUMO

The bacterial spot of tomato, caused by Xanthomonas spp., is a very important disease, especially in the hot and humid periods of the year. The chemical control of the disease has not been very effective for a number of reasons. This study aimed to evaluate, under greenhouse conditions, the efficacy of leaf-spraying chemicals (acibenzolar-S-methyl (ASM) (0.025 g.L⁻¹), fluazinam (0.25 g.L⁻¹), pyraclostrobin (0.08 g.L⁻¹), pyraclostrobin + methiran (0.02 g.L⁻¹ + 2.2 g.L⁻¹), copper oxychloride (1.50 g.L⁻¹), mancozeb + copper oxychloride (0.88 g.L⁻¹ + 0.60 g.L⁻¹), and oxytetracycline (0.40 g.L⁻¹)) on control of bacterial spot. Tomatoes Santa Clara and Gisele cultivars were pulverized 3 days before inoculation with Xanthomonas perforans. The production of enzymes associated with resistance induction (peroxidase, polyphenol oxidase, phenylalanine ammonia-lyase, β-1,3-glucanase, and protease) was quantified from leaf samples collected 24 hours before and 24 hours after chemical spraying and at 1, 2, 4, 6, and 8 days after bacterial inoculation. All products tested controlled bacterial spot, but only ASM, pyraclostrobin, and pyraclostrobin + metiram increased the production of peroxidase in the leaves of the two tomato cultivars, and increased the production of polyphenol oxidase and β-1,3-glucanase in the Santa Clara cultivar..(AU)

Assuntos

RESUMO

Devido à ocorrência de epidemias severas de pústula bacteriana ou mancha bacteriana no pimentão, causada pela bactéria Xanthomonas campestris pv. vesicatoria (Doidge) Dye., o cultivo do pimentão na várzea do Rio Solimões, próximo à Manaus, encontra-se em decadência. O INPA, desde 1976, desenvolve um Programa de Melhoramento Genético do Pimentão visando incorporar resistência ao patógeno. Neste trabalho são relatados os resultados obtidos em três ensaios, nas áreas de terra firme e várzea do Estado do Amazonas, envolvendo progênies F13 e F14 do cruzamento interespecífico entre Capsicum annuum e C. chinense, denominado HP-12, em cujas progênies vêm sendo realizadas seleções genealógicas visando obter variedades resistentes ao patógeno X. campestris pv. vesicatoria e alta capacidade produtiva, sob condição de cultivo em ambientes quentes e úmidos. Quando a população de hospedeiros foi constituída por indivíduos resistentes e suscetíveis, a curva de progresso da doença adaptou-se melhor ao modelo monomolecular, onde níveis mais elevados de resistência, conferidos por um genótipo, foram devidos à sua capacidade de restringir a velocidade do progresso da doença. Nos três ensaios, as progênies selecionadas pelo Programa apresentaram maior resistência e capacidade produtiva, quando comparadas à testemunha suscetível (Cascadura Ikeda), em condições de ocorrência da doença e verificou-se que a capacidade de produção de frutos está relacionada aos níveis de resistência do hospedeiro ao patógeno. Por outro lado, levando-se em conta os caracteres de resistência e capacidade produtiva das progênies inferiu-se que a espécie C. chinense é um recurso genético importante como fonte de resistência a X. campestris pv. vesicatoria nos programas de melhoramento do pimentão.

The cultivation of pepper is decling in the floodplain ecosystem of the Solimões River, near Manaus, Amazonas, Brazil, because the frequence of severe epidemics of bacterial spot caused by X. campestris pv. vesicatoria (Doidge) Dye. The INPA pepper improvement program for resistance to X. campestris pv. vesicatoria was initiated in 1976. In this paper is reported results of three experiments in upland and floodplain ecosystems in Amazonas, in which F13 and F14 progenies of a interspecific cross of Capsicum annuum and C. chinense (named HP-12) were evaluated for resistance to X. campestris pv. vesicatoria and fruit yield potential under natural conditions of plant infection. When the host population is composed of resistant and suceptible cultivars epidemic patterns fit the monomolecular model of disease progress and high levels of resistance, conferred by a genotype, were due to its capacity to restrict the velocity of disease progress. The progenies selected by the program have higher levels of resistance to the pathogen and higher yield potential than control, the susceptible cultivar Cascadura Ikeda. The potential for fruit yield is related to the host's level of resistance. Also C. chinense is an important source of genetic resistance to X. campestris pv. vesicatoria for the pepper genetic improvement program.

Assuntos

RESUMO

The cultivation of pepper is decling in the floodplain ecosystem of the Solimões River, near Manaus, Amazonas, Brazil, because the frequence of severe epidemics of bacterial spot caused by X. campestris pv. vesicatoria (Doidge) Dye. The INPA pepper improvement program for resistance to X. campestris pv. vesicatoria was initiated in 1976. In this paper is reported results of three experiments in upland and floodplain ecosystems in Amazonas, in which F13 and F14 progenies of a interspecific cross of Capsicum annuum and C. chinense (named HP-12) were evaluated for resistance to X. campestris pv. vesicatoria and fruit yield potential under natural conditions of plant infection. When the host population is composed of resistant and suceptible cultivars epidemic patterns fit the monomolecular model of disease progress and high levels of resistance, conferred by a genotype, were due to its capacity to restrict the velocity of disease progress. The progenies selected by the program have higher levels of resistance to the pathogen and higher yield potential than control, the susceptible cultivar Cascadura Ikeda. The potential for fruit yield is related to the host's level of resistance. Also C. chinense is an important source of genetic resistance to X. campestris pv. vesicatoria for the pepper genetic improvement program.

Devido à ocorrência de epidemias severas de pústula bacteriana ou mancha bacteriana no pimentão, causada pela bactéria Xanthomonas campestris pv. vesicatoria (Doidge) Dye., o cultivo do pimentão na várzea do Rio Solimões, próximo à Manaus, encontra-se em decadência. O INPA, desde 1976, desenvolve um Programa de Melhoramento Genético do Pimentão visando incorporar resistência ao patógeno. Neste trabalho são relatados os resultados obtidos em três ensaios, nas áreas de terra firme e várzea do Estado do Amazonas, envolvendo progênies F13 e F14 do cruzamento interespecífico entre Capsicum annuum e C. chinense, denominado HP-12, em cujas progênies vêm sendo realizadas seleções genealógicas visando obter variedades resistentes ao patógeno X. campestris pv. vesicatoria e alta capacidade produtiva, sob condição de cultivo em ambientes quentes e úmidos. Quando a população de hospedeiros foi constituída por indivíduos resistentes e suscetíveis, a curva de progresso da doença adaptou-se melhor ao modelo monomolecular, onde níveis mais elevados de resistência, conferidos por um genótipo, foram devidos à sua capacidade de restringir a velocidade do progresso da doença. Nos três ensaios, as progênies selecionadas pelo Programa apresentaram maior resistência e capacidade produtiva, quando comparadas à testemunha suscetível (Cascadura Ikeda), em condições de ocorrência da doença e verificou-se que a capacidade de produção de frutos está relacionada aos níveis de resistência do hospedeiro ao patógeno. Por outro lado, levando-se em conta os caracteres de resistência e capacidade produtiva das progênies inferiu-se que a espécie C. chinense é um recurso genético importante como fonte de resistência a X. campestris pv. vesicatoria nos programas de melhoramento do pimentão.