Curtobacterium flaccumfaciens PV. flaccumfaciens: aspectos epidemiológicos e variabilidade genética
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Data
2015-12-15
Autores
Gonçalves, Ricardo Marcelo [UNESP]
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Uma das principais doenças bacterianas que acomete a cultura do feijoeiro comum (Phaseolus vulgaris L.) no Brasil é a murcha-de-curtobacterium, causa por Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff). Até o momento são escassas as informações a respeito da sobrevivência da bactéria no cultivo do feijoeiro, fato que pode interferir no manejo e controle da doença, além de informações a respeito da variabilidade genética da bactéria. Assim, esta pesquisa teve por objetivos analisar o potencial de algumas coberturas de inverno como hospedeiras alternativas de Cff, avaliar o efeito destas culturas aplicadas em sistema de rotação com o feijoeiro na incidência e severidade da doença, avaliar o comportamento de genótipos de feijoeiro que melhor se adaptam à doença em regiões do estado do Paraná, verificar a sobrevivência de Cff como células livres no solo e analisar a variabilidade genética da bactéria pela técnica de análise por sequências multilocus (MLSA). Foi observado que Cff pôde colonizar epifiticamente ou endofiticamente a aveia preta, trigo, aveia branca, cevada, azevém e canola. Os cultivos prévios da aveia preta e do trigo propiciaram o aumento da incidência e severidade da doença no feijoeiro, bem como redução no peso médio de 100 grãos. A produtividade média do feijoeiro teve uma redução de 50,64% em uma área com maior intensidade da doença, com parâmetros agronômicos (número de vagens/planta, número de grãos/planta, peso dos grãos/planta e peso de 100 grãos), menores no local com maior incidência da doença. O cultivo prévio do milho e da soja propiciaram redução da incidência de Cff e aumento na produtividade do feijoeiro. As cultivares IPR Juriti e IPR Tuiuiú apresentaram maior nível de resistência à doença e foram as mais produtivas no Paraná. Houve diferença do período de sobrevivência como células livres entre isolados de Cff no solo (22 a 34 dias) e entre diferentes solos (30 a 94 dias). A sobrevivência no solo sob condições de campo variou de 34 a 80 dias, sendo observada a influência da temperatura e umidade no período de sobrevivência a campo. A técnica molecular empregada para detecção de Cff diretamente do solo possibilitou detecções em concentrações mínimas de 5x105 a 5x106 UFC/g de solo, sendo que Cff não foi detectada nos solos dos ensaios de campo conduzidos em 2012 e 2013, no Paraná. O estudo de MLSA com seis genes housekeeping evidenciou grande diversidade genética entre isolados de Curtobacterium flaccumfaciens coletados de diferentes países e hospedeiros, possivelmente devido recombinações e seleção purificadora durante o processo evolutivo da espécie; foi observado que não há correlação entre classificação filogenética com o local e hospedeiro.
One of the most important diseases of common bean in Brazil is the bacterial wilt, caused by Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff). Until now, there is no much knowledge about how this bacterium survives on common bean, fact that could interfere with the disease management, besides of information about genetic variability of the bacterium. In this work we studied the potential of some winter crops as alternative hosts of Cff; the effect of these crops in the incidence and severity of bacterial wilt in rotation with common bean; detection of common bean cultivars with resistance levels to Cff in regions of Paraná State; study the survival of Cff as free cells in the soil; and assess the genetic variability of the bacterium by multilocus sequence analysis (MLSA). Cff colonized epiphytically and endophytically black oat, wheat, white oat, barley, ryegrass and canola. The previous crop of black oat and wheat increased the incidence and severity of bacterial wilt and reduced the average weight of 100 grains. The average production of common bean decreased 50,64% in area with higher intensity of disease, with reduction of number of pods/plant, number of grains/plant, weigh of grains/plant and weigh of 100 bean grains. The previous crop of corn and soybean reduced the Cff incidence and increased the bean production. The cultivars IPR Juriti and IPR Tuiuiú shown greater level of reistance for bacterial wilt and were more productive in Paraná State. Cff strains showed different survival periods in the soil (22 to 34 days) and was influenced by the soil type (30 to 94 days). For the field experiments, the survival of Cff varied from 34 to 80 days, being influenced by the temperature and moisture. The molecular technique employed to detect Cff directly from soil enabled detection in concentrations ranging from 5x105 to 5x106 CFU/g of soil and Cff was not detected on field assays in 2012 and 2013, in Paraná State. The study of MLSA with six housekeeping genes revealed large genetic diversity between strains of Curtobacterium flaccumfaciens from different countries and hosts, possibly due recombinations and purifying selection during the evolutive process of the specie; no correlation between phylogenetic classification with local and host of origin were observed.
One of the most important diseases of common bean in Brazil is the bacterial wilt, caused by Curtobacterium flaccumfaciens pv. flaccumfaciens (Cff). Until now, there is no much knowledge about how this bacterium survives on common bean, fact that could interfere with the disease management, besides of information about genetic variability of the bacterium. In this work we studied the potential of some winter crops as alternative hosts of Cff; the effect of these crops in the incidence and severity of bacterial wilt in rotation with common bean; detection of common bean cultivars with resistance levels to Cff in regions of Paraná State; study the survival of Cff as free cells in the soil; and assess the genetic variability of the bacterium by multilocus sequence analysis (MLSA). Cff colonized epiphytically and endophytically black oat, wheat, white oat, barley, ryegrass and canola. The previous crop of black oat and wheat increased the incidence and severity of bacterial wilt and reduced the average weight of 100 grains. The average production of common bean decreased 50,64% in area with higher intensity of disease, with reduction of number of pods/plant, number of grains/plant, weigh of grains/plant and weigh of 100 bean grains. The previous crop of corn and soybean reduced the Cff incidence and increased the bean production. The cultivars IPR Juriti and IPR Tuiuiú shown greater level of reistance for bacterial wilt and were more productive in Paraná State. Cff strains showed different survival periods in the soil (22 to 34 days) and was influenced by the soil type (30 to 94 days). For the field experiments, the survival of Cff varied from 34 to 80 days, being influenced by the temperature and moisture. The molecular technique employed to detect Cff directly from soil enabled detection in concentrations ranging from 5x105 to 5x106 CFU/g of soil and Cff was not detected on field assays in 2012 and 2013, in Paraná State. The study of MLSA with six housekeeping genes revealed large genetic diversity between strains of Curtobacterium flaccumfaciens from different countries and hosts, possibly due recombinations and purifying selection during the evolutive process of the specie; no correlation between phylogenetic classification with local and host of origin were observed.
Descrição
Palavras-chave
Phaseolus vulgaris, Bean bacterial wilt, Ecological niches, Resistance, Survival, MLSA, Phaseolus vulgaris, Murcha-de-curtobacterium, Nichos ecológicos, Sobrevivência, MLSA