RESUMO A murcha bacteriana limita a produção do tomateiro sob condições de alta temperatura e umidade, e porta-enxertos resistentes são importantes para o manejo integrado da doença. Visto que existe interação entre isolados locais e genótipos de tomateiros, objetivou-se avaliar 14 porta-enxertos de tomateiro à murcha bacteriana na mesorregião da Mata de Pernambuco, Brasil. A reação dos porta-enxertos a dois sequevares de Ralstonia solanacearum e dois de R. pseudosolanacearum foi avaliada em quatro experimentos realizados em casa de vegetação em delineamento inteiramente casualizado, com quatro repetições, com quatro plantas cada. Sete genótipos foram selecionados para avaliar a reação à doença como porta-enxertos de tomateiro ‘Tomini F1’ em uma área de produção com histórico da doença em Chã Grande, Pernambuco, Brasil, utilizando delineamento em blocos casualizados, com quatro plantas por tratamento por bloco. Não foram observados sintomas da doença nas plantas enxertadas em ‘Guardião’, ‘Woodstock’ e ‘Yoshimatsu’. Considerando todos os experimentos, ‘Guardião’ e ‘Muralha’ apresentaram os melhores níveis de resistência, podendo ser utilizados no manejo integrado da murcha bacteriana e estudados em programas de melhoramento.

ABSTRACT Bacterial wilt limits tomato production and resistant rootstocks could be important for the integrated management of the disease. Since there is an interaction between local bacterial strains and tomato genotype, this study aimed to evaluate 14 tomato rootstocks to bacterial wilt in the Mata mesoregion of Pernambuco state, Brazil. The rootstocks reaction to two sequevars of Ralstonia solanacearum and two of R. pseudosolanacearum was evaluated in four experiments carried out in the greenhouse using the completely randomized experimental design, with four replications composed of four plants each. Seven genotypes were selected to evaluate the reaction to bacterial wilt as rootstocks grafting in tomato plants ‘Tomini F1’ in a production area with disease history in the Chã Grande municipality, using randomized block design with four plants per treatment in each block. In the field experiment, disease symptoms were not observed in the grafted plants in ‘Guardião’, ‘Woodstock’, and ‘Yoshimatsu’. Regarding all experiments, ‘Guardião’ and ‘Muralha’ showed the best resistance levels and could be used in the integrated management of bacterial wilt and studied in plant breeding programs.

Abstract Banana vascular wilt or Moko is a disease caused by Ralstonia solanacearum. This study aimed to sequence, assemble, annotate, and compare the genomes of R. solanacearum Moko ecotypes of different sequevar strains from Brazil. Average nucleotide identity analyses demonstrated a high correlation (> 96%) between the genome sequences of strains CCRMRs277 (sequevar IIA-24), CCRMRs287 (IIB-4), CCRMRs304 (IIA-24), and CCRMRsB7 (IIB-25), which were grouped into phylotypes IIA and IIB. The number of coding sequences present in chromosomes and megaplasmids varied from 3,070 to 3,521 and 1,669 to 1,750, respectively. Pangenome analysis identified 3,378 clusters in the chromosomes, of which 2,604 were shared by all four analyzed genomes and 2,580 were single copies. In megaplasmids, 1,834 clusters were identified, of which 1,005 were shared by all four genomes and 992 were identified as single copies. Strains CCRMRsB7 and CCRMRs287 differed from the others by having unique clusters in both their chromosomes and megaplasmids, and CCRMRsB7 possessed the largest genome among all Moko ecotype strains sequenced to date. Therefore, the genomic information obtained in this study provides a theoretical basis for the identification, characterization, and phylogenetic analysis of R. solanacearum Moko ecotypes.

RESUMO A podridão escorregadia da cebola (Allium cepa) ocasionada pela bactéria Burkhoderia gladioli pv. alliicola é uma das doenças de origem bacteriana que se destaca nas regiões produtoras do semiárido do Nordeste brasileiro. Tendo em vista a importância da doença, a ausência de variedades resistentes e a potencial ameaça desta enfermidade à cebolicultura, este estudo teve como objetivo avaliar a reação de genótipos de cebola à doença. Nove isolados de B. gladioli pv. alliicola foram inoculados artificialmente em bulbos de cebola cv. Baia Periforme e os três isolados mais agressivos (CCRMBG39, CCRMBG172 e CCRMBG212) foram selecionados para avaliar a resistência à doença. Cinquenta e oito genótipos de cebola foram avaliados utilizando o isolado mais agressivo (CCRMBG39), sendo 34 genótipos considerados tolerantes, com severidade variando de 9,79 a 13,42 mm. Os 15 genótipos mais promissores e o genótipo mais suscetível foram selecionados para estudar a estabilidade da resistência utilizando-se os três isolados selecionados. Os genótipos F2 (EHCEB 20151030 x EHCEB 20133015), Cascuda T5, Crioula Mercosul, Juporanga, EHCEB 20111036, Cascuda T6 e EHCEB 20142028 mantiveram-se estáveis quanto a tolerância à doença quando inoculados com os três isolados, apresentando severidade variando de 9,13 a 14,19 mm. Diante desses resultados, concluímos que esses genótipos apresentaram-se como potenciais fontes de tolerância à podridão escorregadia da cebola.

ABSTRACT Onion’s (Allium cepa) slippery skin caused by Burkholderia gladioli pv. alliicola is one of the bacterial diseases that stand out in producing regions of the Brazilian Northeast. Given the importance and potential threat of this disease, and the absence of resistant varieties, the aim of this study was to evaluate the reaction of onion genotypes to slippery skin and to analyze the tolerance stability of the most promising genotypes to different strains of the bacteria. Nine strains of B. gladioli pv. alliicola were artificially inoculated in onion bulbs cv. Baia Periforme and the three most aggressive strains (CCRMBG39, CCRMBG172 and CCRMBG212) were selected to evaluate the tolerance to the disease. Fifty-eight onion genotypes were challenged with the most aggressive strain (CCRMBG39) and 34 genotypes were considered as tolerant, with a disease severity varying from 9.79 to 13.42 mm. The fifteen most promising genotypes and the most susceptible genotype were selected to study the stability of tolerance using the three selected strains. The genotypes F2 (EHCEB 20151030 x EHCEB 20133015), Cascuda T5, Crioula Mercosul, Juporanga, EHCEB 20111036, Cascuda T6 and EHCEB 20142028 remained tolerant to the disease when inoculated with the three strains, with a disease severity ranging from 9.13 to 14.19 mm. In view of these results, we conclude that these genotypes can be used as potential sources of tolerance to onion slippery skin.

Abstract Ralstonia solanacearum is the causal agent of Moko disease in bananas, which in the state of Sergipe in northeastern Brazil causes “Sergipe facies”. This disease induces atypical symptoms similar to those of Bugtok disease in the Philippines. This study was conducted to sequence, assemble, and annotate the genomes of the Sergipe facies-causing isolates SFC and IBSBF2570 (sequevar IIA-53) and compare their genomes with two representative isolates causing Bugtok disease. The genomes were sequenced and assembled, resulting in lengths of 5.58 Mb (SFC) and 5.46 Mb (IBSBF2570) in 185 and 174 contigs, respectively. The isolates of Sergipe facies and Bugtok disease showed similarities in their gene contents. We identified 5,668 information clusters, 3,752 of which were shared by all genomes (core genes). Moreover, 3,585 single-copy genes were identified. Isolates causing Bugtok disease exclusively shared 266 more information clusters than the isolates causing Sergipe facies. These results suggest that Sergipe facies and Bugtok disease isolates show high genomic similarity. However, the similarity is even greater between the Bugtok disease isolates. This may be because of their longer period of interaction compared to Sergipe facies isolates.

ABSTRACT Bacterial fruit blotch (BFB) of cucurbit plants is caused by Acidovorax citrulli and represents a serious concern to melon (Cucumis melo L.) growers worldwide, including those in Brazil. Thirty-four A. citrulli strains from different melon production areas of northeastern Brazil were characterized for their virulence on melon fruits and their substrate utilization and molecular profiles. Based on the analysis of BFB severity on melon fruits, the A. citrulli strains were divided into three groups, classified as mildly, moderately or highly virulent. Although host-related groups were not observed, the watermelon and ‘melão-pepino’ strains exhibited only low or moderate virulence on melon fruit. Substrate utilization profiles revealed that 94 % of the 95 tested compounds were used by A. citrulli strains as a carbon source. Overall, based on substrate utilization, low variability was observed with no relationship to host of origin. The formation of one group of A. citrulli strains based on Repetitive Sequence-based PCR (rep-PCR) analysis confirmed the low variability observed in the substrate utilization analyses. Bayesian inference based on the analysis of 23S rDNA partial sequence data resulted in one well-supported clade and clustered the strains with the A. citrulli-type species with high posterior probability support. Based on the markers used, the Brazilian A. citrulli strains belong to a single group, which corresponds to the previously described Group I for this bacterium in the United States.

Este estudo teve como objetivo identificar possíveis hospedeiras alternativas de Xanthomonas campestris pv. viticola (Xcv), visando a fornecer subsídios para o manejo do cancro bacteriano da videira. Vinte e seis espécies vegetais foram inoculadas artificialmente com o isolado Xcv3 e mantidas em condições de casa de vegetação, sendo avaliada a evolução sintomatológica da doença, como manchas necróticas angulares e lesões nas nervuras. O Xcv3 foi reisolado a partir de cada hospedeiro alternativo com sintomas, sendo identificado por PCR (Polymerase Chain Reaction), com iniciadores específicos. As espécies inoculadas que apresentaram os sintomas típicos da doença foram Glycine sp., Senna obtusifolia, Desmodium discolor, Amaranthus deflexus, Azadirachta indica, Solanum lycopersicum e Vigna unguiculata. As espécies da família Poaceae, Bidens pilosa, Emilia fosbergii, Praxelis pauciflora, Macroptilium lathyroides e Portulaca oleracea não apresentaram sintomas durante o período da avaliação.

This study aimed to identify potential alternative hosts of Xanthomonas campestris pv. viticola (Xcv), to provide data for the management of bacterial canker of grapevine. Twenty-six plant species were artificially inoculated with the strain Xcv3 and maintained under greenhouse conditions where the development of disease symptoms, such as angular necrotic spots and rib lesions were evaluated. The Xcv3 was reisolated from each symptomatic alternative host, and identified using PCR (Polymerase Chain Reaction) with specific primers. The inoculated species that showed typical disease symptoms were Glycine sp., Senna obtusifolia, Desmodium discolor, Amaranthus deflexus, Azadirachta indica, Solanum lycopersicum and Vigna unguiculata. Species of the family Poaceae, Bidens pilosa, Emilia fosbergii, Praxelis pauciflora, Macroptilium lathyroides and Portulaca oleracea were not showed during the period of evaluation.

Foi estudado o efeito de acibenzolar-S-metil (ASM), mananoligossacarídeos (MOS) e bioflavonóides cítricos (BFC) no controle da mancha-aquosa causada por Acidovorax citrulli em meloeiros tipo Amarelo (híbrido AF4945) e tipo Pele de Sapo (híbrido Nilo), em diferentes épocas de aplicação (10 e 15 dias após a emergência das plântulas) e dosagens (ASM 25; 50 e 75 mg i.a. L-1; MOS 0,5; 1,0 e 1,5 p.c. L-1; BFC 2; 3 e 4 mL p.c. L-1); e também no crescimento da planta em solo com ou sem suplementação de NPK. A melhor época para aplicação dos indutores foi dez dias após a emergência das plântulas. Considerando os dois genótipos, ASM (50 mg i.a. L-1) e BFC (3 mL p.c. L-1) elevaram o período de incubação em até 13 e 8 dias e reduziram a incidência da mancha-aquosa em 88 e 60%; o índice de doença em 96 e 88%; e a área abaixo da curva de progresso da doença em 94 e 74%, respectivamente. No entanto, independente do nível de NPK no solo, ASM e BFC reduziram a altura, biomassa fresca e seca da parte aérea das plantas de meloeiro em até 24; 41 e 34%, respectivamente.

The effect of acibenzolar-S-methyl (ASM), mannano-oligosaccharides (MOS) and citrus bioflavonoids (BFC) was studied for control of bacterial fruit blotch of yellow melon (hybrid AF4945) and Pele de Sapo melon (hybrid Nilo), evaluating different application periods (10 and 15 days after plant emergence), and dosages (acibenzolar-S-methyl 25; 50 and 75 mg a.i. L-1; mannano-oligosaccharides 0.5; 1.0 and 1.5 c.p. L-1; citrus bioflavonoids 2; 3 and 4 mL c.p. L-1) and also on plant growth in soil supplemented or not with NPK. The best period for application was 10 days after plant emergence. Considering both genotypes, ASM (50 mg a.i. L-1) and BFC (3 mL c.p. L-1) increased incubation period until 13 and 8 days and reduced disease incidence by 88 and 60%; disease index by 96 and 88%; and area under disease progress curve by 94 and 74%, respectively. However, independent of NPK level in the soil ASM and BFC reduced melon plant height by 24%; they also reduced fresh and dry shoot biomass by 41% and 34%, respectively.