Biochemical aspects of the interaction cabbage-Xanthomonas campestris pv. campestris

O repolho (Brassica oleracea var. capitata) está entre as hortaliças mais produzidas e consumidas em todo o mundo. Xanthomonas campestris pv. campestris (Xcc) é o agente causal da podridão negra das brássicas, a doença mais destrutiva da cultura do repolho. O plantio de variedades resistentes é uma medida simples e barata para o controle de doenças de plantas. Fontes de resistência à podridão negra são escassas no genoma de B. oleracea. No entanto, o plantio de cultivares com maiores níveis de resistência ou a aplicação de indutores de resistência pode auxiliar no controle da doença. Embora essas medidas de controle sejam viáveis, estudos sobre os mecanismos de defesa basal de natureza bioquímicas do repolho e da indução de resistência à podridão negra são raros na literatura. O presente estudo visou encontrar variedades com maiores níveis de resistência à doença, observar a variabilidade patogênica de isolados de Xcc em relação a diferentes cultivares de repolho, verificar diferenças nas respostas bioquímicas de defesa do repolho a diferentes isolados de Xcc, verificar diferenças nas respostas bioquímicas de defesa de cultivares repolho com diferentes níveis de resistência à doença incitada por um isolado de Xcc, e observar a eficiência do Acibenzolar-S-Metil (ASM) no controle da podridão negra em repolho. Os cultivares ‘Fuyutokyo Kobayashi’, ‘Midori’ e ‘Coração de Boi Gigante’ apresentaram maiores níveis de resistência à podridão negra e os cultivares ‘Esmeralda’ e ’60 dias’ se mostraram altamente suscetíveis. Xcc induziu respostas de defesa em repolho, embora isolados mais agressivos foram capazes de modular essas respostas. Cultivares de repolho mais resistentes à podridão negra sofreram alterações significativas nas atividades das enzimas de defesa. As alterações que ocorreram em cultivares mais suscetíveis não foram suficientes para conter o processo infeccioso de Xcc. Plantas de repolho tratadas com ASM exibiram atividades enzimáticas significativamente maiores do que as não tratadas e apresentaram menor severidade da doença.Cabbage (Brassica oleracea var. capitata) is among the most produced and consumed vegetables in the world. Xanthomonas campestris pv. campestris (Xcc) is the causal agente of the black rot of brassicas, the most destructive disease in cabbage crop. Planting resistant varieties is a simple and cheap way to control plant diseases. Sources of resistance to the black rot are scarce in the B. oleracea genome. However, planting varieties with higher resistance levels or applying resistance inducers may help to control the disease. Although these control measures are viable, studies on the basal defense mechanisms of biochemical nature in cabbage and resistance induction against black rot are rare in the literature. The present study aimed to find cultivars with higher resistance levels to the disease, determine the pathogenic variability of Xcc isolates in relation to different cabbage cultivars, verify differences in the cabbage biochemical defense responses with different resistance levels to the disease incited by a Xcc isolate, and observe the efficiency of Acibenzolar-S-Methyl (ASM) to control of the black rot in cabbage. Cultivars ‘Fuyutokyo Kobayashi’, ‘Midori’ and ‘Coração de Boi Gigante’ were more resistant to black rot and the cultivars ‘Esmeralda’ e ’60 dias’ were highly susceptible and may be used in pathogenicity tests for Xcc detection. Xcc induced defense responses in cabbage, however more aggressive isolates were able to modulate these defense responses. Cabbage cultivars more resistant to the black rot had significant alterations in the defense enzymes activities. The alterations that occurred in the more susceptible cultivars were not sufficient to contain the infectious process of Xcc. Cabbage plants treated with ASM exhibited enzymatic activities meaningfully higher than those non-treated and showed lower disease severity

Assessment of semiselective media and molecular tools for detection of Xanthomonas campestris pv. campestris

Avaliou-se a eficiência de meios de cultura semi-seletivos, de testes de patogenicidade e a especificidade de primers para a detecção de Xanthomonas campestris pv. campestris (Xcc). Para a execução dos experimentos, foram utilizados 29 isolados recebidos de diferentes regiões do Brasil. Para a confirmação da identidade dos isolados foram realizados os testes de produção de xantomonadinas e de utilização de asparagina, análise da região 16s do genoma bacteriano e testes de patogenicidade. Dos 29 isolados, 24 foram identificados como pertencentes ao gênero Xanthomonas. Nenhum dos isolados induziu HR nas plantas inoculadas e apenas 14 isolados induziram sintomas típicos da podridão negra em couve. O meio NSCAA foi o único capaz de suportar o crescimento de todos os isolados, enquanto os meios mCS20ABN, YTSA-CC e Xan-D permitiram o crescimento da maioria dos isolados. À exceção do isolado X03, os primers XCR/XCF e HrcCR2/HrcCF2 permitiram a amplificação e visualização das bandas de tamanhos esperados para Xcc.It was aimed to evaluate the efficiency of semi-selective media, for pathogenicity tests and primers specificity for detection of Xanthomonas campestris pv. campestris (Xcc). For execution of experiments, we used 29 strains received from different regions in Brazil. For confirmation of the identity of the strains we carried out xanthomonadins production test, asparagine utilization, analysis of the 16S rDNA genes region of bacterial genome and pathogenicity tests. Of the 29 strains, 24 were identified as belonging to Xanthomonas genus. None of the strains induced hypersensitivity reaction (HR) in inoculated plants and only 14 strains induced typical symptoms of black rot in collard. The NSCAA medium was the uniquely to support the growth of all strains, whereas mCS20ABN, YTSA-CC and Xan-D media allowed the growth of most of strains. Except of X03 strain, the XCR/XCF and HrcCR2/HrcCF2 primers allowed the amplification and visualization of bands of expected size to Xcc

Brazilian Science between National and Foreign Journals: Methodology for Analyzing the Production and Impact in Emerging Scientific Communities

<div><p>In recent decades, we have observed an intensification of science, technology and innovation activities in Brazil. The increase in production of scientific papers indexed in international databases, however, has not been accompanied by an equivalent increase in the impact of publications. This paper presents a methodology for analyzing production and the impact of certain research areas in Brazil related to two aspects: the origin of the journals (national or foreign) and international collaboration. These two variables were selected for being of particular importance in understanding the context of scientific production and communication in countries with emerging economies. The sample consisted of papers written by Brazilian researchers in 19 subfields of knowledge published from 2002 to 2011, totaling 85,082 papers. To calculate the impact, we adopted a normalized indicator called the relative subfield citedness (Rw) using a window of 5 years to obtain measurements evaluated in 2 different years: 2007 and 2012. The data on papers and citations were collected from the Web of Science database. From the results, we note that most of the subfields have presented, from one quinquennium to another, improved performance in the world production rankings. Regarding publication in national and foreign journals, we observed a trend in the distribution maintenance of production of the subfields based on the origin of the journal. Specifically, for impact, we identified a lower Rw pattern for Brazilian papers when they were published in national journals in all subfields. When Brazilian products are published in foreign journals, we observed a higher impact for those papers, even surpassing the average global impact in some subfields. For international collaboration, we analyzed the percentage of participation of foreign researchers and the connection between collaboration and the impact of papers, especially emphasizing the distinction of hyperauthorship papers in terms of production and impact.</p></div

Brazilian Rw by type of journal in 2007 and 2012.

<p>[Data sourced from Thomson Reuters Web of Science].</p

International collaboration and its influence on the impact of papers published in foreign journals.

<p>^aThe “Social Sciences, Interdisciplinary” subfield was not included in the analysis due to its negligible quantity of papers with international collaboration published in foreign journals. [Data sourced from Thomson Reuters Web of Science].</p