Nichos de sobrevivência e disseminação de Xanthomonas campestris pv. campestris, agente causal da podridão negra das brássicas
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2020-03-12
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Universidade Estadual Paulista (Unesp)
Resumo
A podridão negra, causada por Xanthomonas campestris pv. campestris (Xcc), é considerada a doença bacteriana mais importante das brássicas no mundo. Apesar dos esforços para o manejo, sua ocorrência é comum em cultivos de brássicas. O conhecimento dos nichos de sobrevivência e mecanismos de disseminação de Xcc são de extrema importância para o manejo eficiente da podridão negra. Este trabalho avaliou a sobrevivência de Xcc em nichos ecológicos, assim como o potencial de disseminação da bactéria por insetos. Para identificar as plantas daninhas que podem favorecer a sobrevivência epifítica de Xcc, assim como novas hospedeiras sintomáticas da bactéria, coletas foram realizadas em seis campos de cultivo de brássicas do estado de São Paulo, em 2017 e 2018. A capacidade endofítica do isolado 3098C de Xcc, resistente a rifampicina, foi avaliada em quatro experimentos em casa de vegetação, entre 2017 e 2019, utilizando-se 23 espécies de plantas daninhas e dois métodos de inoculação. Em campo, quatro experimentos foram instalados entre 2017 e 2019 para avaliar a sobrevivência de Xcc na filosfera e rizosfera de 20 espécies de plantas cultivadas. A sobrevivência do isolado 3098C na rizosfera do repolho cultivado em seis tipos de solos também foi avaliada, em quatro experimentos. Além da sobrevivência, a disseminação de Xcc por Bemisia tabaci e Myzus persicae foi avaliada em experimentos em condições controladas. Como resultados, 30 espécies de plantas daninhas de 14 famílias botânicas foram coletadas dos seis campos de cultivo de brássicas, sendo Xcc recuperada da filosfera de 25 espécies. Em plantas sintomáticas, a bactéria foi isolada de Bidens pilosa (picão preto), Coronopus didymus (mentruz rasteiro), Galinsoga parviflora (picão branco), Ipomoea nil (corda de viola), Lepidium virginicum (mentruz), Raphanus raphanistrum (nabiça), Raphanus sativus (nabo forrageiro) e Sonchus oleraceus (serralha). Nos experimentos em casa de vegetação, Xcc foi recuperada de todas as plantas daninhas, porém os períodos de sobrevivência endofítica variaram entre as espécies. A presença de ferimentos pode ter favorecido a sobrevivência endofítica de Xcc nos tecidos de algumas espécies. Na filosfera das plantas cultivadas, a bactéria sobreviveu por até 70 dias no repolho, tomate, trigo, aveia preta, nabo forrageiro e pimentão, por até 63 dias em abóbora e mostarda, e por até 56 dias no feijão. Na rizosfera das plantas cultivadas, Xcc apresentou baixa sobrevivência em comparação ao solo na ausência de plantas para a maioria das espécies avaliadas, sendo o maior período de sobrevivência observado na rizosfera do repolho (70 dias). Baixa sobrevivência da bactéria ocorreu na rizosfera do repolho quando cultivado em diferentes solos. Bemisia tabaci e M. persicae aparentemente não estão envolvidos na disseminação de Xcc.
Black rot, caused by Xanthomonas campestris pv. campestris (Xcc), is considered the most important bacterial disease of brassica worldwide. Despite management efforts, its occurrence is common in brassica crops. Knowledge of survival niches and Xcc dissemination mechanisms are extremely important for the efficient management of black rot. This study evaluated Xcc survival in ecological niches, as well as the potential for the bacterium dissemination by insects. To identify the weeds that may favor Xcc epiphytic survival, as well as new symptomatic hosts of the bacterium, collections were carried out in six brassica crop fields in São Paulo State, in 2017 and 2018. The endophytic capacity of Xcc 3098C strain, resistant to rifampicin, was evaluated in four greenhouse experiments between 2017 and 2019, using 23 weed species and two inoculation methods. In the field, four experiments were conducted between 2017 and 2019 to assess Xcc survival in the phyllosphere and rhizosphere of 20 crop species. The survival of 3098C strain in cabbage rhizosphere, grown in six soils types, was also evaluated in four experiments. In addition to survival, Xcc dissemination by Bemisia tabaci and Myzus persicae was evaluated in experiments under controlled conditions. As a result, 30 weed species from 14 botanical families were collected from the six brassica crop fields, and Xcc was recovered from the phyllosphere of 25 species. In symptomatic plants, the bacterium was isolated from Bidens pilosa (hairy beggarticks), Coronopus didymus (swinecress), Galinsoga parviflora (gallant soldier), Ipomoea nil (whiteedge morning-glory), Lepidium virginicum (virginia pepperweed), Raphanus raphanistrum (wild radish), Raphanus sativus (cultivated radish) and Sonchus oleraceus (common sowthistle). In greenhouse experiments, Xcc was recovered from all weeds, but the periods of endophytic survival varied among species. The presence of wounds may have favored Xcc endophytic survival in some species tissues. In crops phyllosphere, the bacterium survived for up to 70 days in cabbage, tomato, wheat, black oat, turnip and pepper, for up to 63 days in pumpkin and mustard, and for up to 56 days in beans. In crops rhizosphere, Xcc showed low survival compared with the soil without plants for most of the species evaluated, being the longest survival period observed in cabbage rhizosphere (70 days). Low bacterial survival occurred in cabbage rhizosphere when grown in different soils. Bemisia tabaci and M. persicae are apparently not involved in Xcc dissemination.
Black rot, caused by Xanthomonas campestris pv. campestris (Xcc), is considered the most important bacterial disease of brassica worldwide. Despite management efforts, its occurrence is common in brassica crops. Knowledge of survival niches and Xcc dissemination mechanisms are extremely important for the efficient management of black rot. This study evaluated Xcc survival in ecological niches, as well as the potential for the bacterium dissemination by insects. To identify the weeds that may favor Xcc epiphytic survival, as well as new symptomatic hosts of the bacterium, collections were carried out in six brassica crop fields in São Paulo State, in 2017 and 2018. The endophytic capacity of Xcc 3098C strain, resistant to rifampicin, was evaluated in four greenhouse experiments between 2017 and 2019, using 23 weed species and two inoculation methods. In the field, four experiments were conducted between 2017 and 2019 to assess Xcc survival in the phyllosphere and rhizosphere of 20 crop species. The survival of 3098C strain in cabbage rhizosphere, grown in six soils types, was also evaluated in four experiments. In addition to survival, Xcc dissemination by Bemisia tabaci and Myzus persicae was evaluated in experiments under controlled conditions. As a result, 30 weed species from 14 botanical families were collected from the six brassica crop fields, and Xcc was recovered from the phyllosphere of 25 species. In symptomatic plants, the bacterium was isolated from Bidens pilosa (hairy beggarticks), Coronopus didymus (swinecress), Galinsoga parviflora (gallant soldier), Ipomoea nil (whiteedge morning-glory), Lepidium virginicum (virginia pepperweed), Raphanus raphanistrum (wild radish), Raphanus sativus (cultivated radish) and Sonchus oleraceus (common sowthistle). In greenhouse experiments, Xcc was recovered from all weeds, but the periods of endophytic survival varied among species. The presence of wounds may have favored Xcc endophytic survival in some species tissues. In crops phyllosphere, the bacterium survived for up to 70 days in cabbage, tomato, wheat, black oat, turnip and pepper, for up to 63 days in pumpkin and mustard, and for up to 56 days in beans. In crops rhizosphere, Xcc showed low survival compared with the soil without plants for most of the species evaluated, being the longest survival period observed in cabbage rhizosphere (70 days). Low bacterial survival occurred in cabbage rhizosphere when grown in different soils. Bemisia tabaci and M. persicae are apparently not involved in Xcc dissemination.
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Bactéria, Plantas daninhas, Plantas cultivadas, Solo, Insetos, Bacterium, Weeds, Cultivated plants, Soil, Insects