Development of species-specific primers for detection of Xanthomonas campestris pv. campestris causing black rot of crucifers

Aim: Black rot of crucifers caused by Xanthomonas campestris pv. campestris (Pammel) Dowson (Xcc) is a major seed-borne disease. The present study aimed to develop a rapid diagnostic protocol for the specific and sensitive detection of this pathogen. Methodology: A specific primer set was designed based on rpf gene and optimization of PCR condition was done for specific detection of Xcc. Sensitivity of PCR for primer set was then determined by diluting the Xcc DNA and cells. Results: Specific primer set was able to amplify a specific band of 304 bp in all 11 isolates of Xcc but failed to amplify other Xanthomonas species and one each of Ralstonia solanacearum, Erwinia caratovora subsp. caratovora, Bacillus subtilis, Pseudomonas fluorescens and P. aeruginosa. The primer set was highly sensitive as it was able to detect 10 pg μl-1 bacterial DNA and up to 3x103 CFU ml-1 corresponding to 12 viable cells of Xcc which were used as template for PCR reaction Interpretation: The results suggest that developed PCR primers are highly specific and sensitive and it can be used to detect the pathogen at an early stage of infection for disease management.

MarR family transcription regulator HpaR and XC0449 coordinately regulate the virulence of Xanthomonas campestris pv. campestris / 生物工程学报

MarR family transcription regulators are ubiquitous among bacteria and archaea. They extensively control multiple cellular processes and elaborately regulate the expression of genes involved in virulence, stress response and antibiotics at translational level. In Xanthomonas campestris pv. campestris, insertional inactivation of MarR family transcription regulator HpaR (XC2827) resulted in significantly decrease in virulence and increase in the production of the extracellular proteases. Here, we reported that the genome of Xcc 8004 encodes nine MarR family transcription regulators. The MarR family transcription regulators, HpaR (XC2827) and XC0449, were heterologous expressed and purified. In vitro MST and Pull-down assay confirmed the physical interaction between HpaR and XC0449. Phenotypical assay determined that deletion of XC0449 resulted in substantial virulence attenuation. In vitro EMSA, in vivo qRT-PCR and GUS activity assay identified that HpaR and XC0449 coordinately act as the transcriptional activator to regulate the expression of the virulence-associated gene XC0705, and eventually control the bacterial virulence and the production of extracellular proteases.

Desempenho de cultivares de couve-flor de verão em Ipameri / Performance of cultivars of cauliflower summer in Ipameri

Com o propósito de avaliar o comportamento de seis cultivares de couve-flor de verão, quanto à produção e resistência à podridão negra (Xanthomonas campestris pv. campestris), instalou-se um experimento em campo, em Ipameri-GO, com o delineamento experimental em blocos completos casualizados com seis tratamentos e quatro repetições. Cada parcela experimental, de 10m², constou de 20 plantas distribuídas no espaçamento de 1,0m entre linhas e 0,5m entre plantas. Foram avaliadas as cultivares: híbridos 'Cindy', 'Sarah AF-1169', 'Sharon', 'Verona', 'Lisvera' e a variedade Piracicaba precoce. Os híbridos Verona e Sharon mostraram-se promissores para cultivo nas condições edafoclimáticas em que foram avaliados, com produtividades de 34,17 e 30,64t ha-1, respectivamente, e com moderados níveis de resistência à podridão negra. A variedade Piracicaba precoce apresentou produção inferior às dos melhores híbridos avaliados e moderada resistência à podridão negra. O híbrido Sarah não é recomendado para plantio na região de Ipameri-GO por apresentar baixa produção e baixa resistência à podridão negra.

In order to evaluate the behavior of six cultivars of cauliflower summer, as production and resistance to black rot (Xanthomonas campestris pv. campestris), installed a field experiment in Ipameri-GO, with the experimental in randomized complete blocks with six treatments and four replications. Each plot of 10m², consisting of 20 plants distributed at a spacing of 1.0m between rows and 0.5m between plants. We evaluated the cultivars: hybrids 'Cindy', 'Sarah AF-1169', 'Sharon', 'Verona', 'Lisvera' and the variety Piracicaba precoce. Hybrids Verona and Sharon proved promising for cultivation in the environmental conditions that were evaluated, with yields of 34.17 and 30.64t ha-1 respectively, and moderate levels of resistance to black rot. The variety Piracicaba precoce showed lower production of the best hybrids and moderate resistance to black rot. The hybrid Sarah is not recommended for planting in the region of Ipameri-GO due to its low production and low resistance to black rot.