A. K. N. Ishida

Rizobactérias no controle da mancha angular do algodoeiro

Avaliou-se o potencial de rizobacterias na inducao de resistencia do algodoeiro a Xanthomonas axonopodis pv. malvacearum. Apos o isolamento das rizobacterias, foram selecionados os isolados capazes de reduzir os sintomas da mancha angular bacteriana em casa de vegetacao, os quais foram aplicados espacialmente separados do patogeno desafiador. Os melhores isolados foram testados quanto a capacidade de reduzir os sintomas da ramulose e da murcha de Verticillium e de inibir diretamente os patogenos in vitro. Do total de 123 isolados de rizobacterias foram selecionados cinco, L2-1 (Bacillus cereus), MT5-6 (Bacillus cereus), L2-2 (Achromobacter xylosoxidans), MT5-5 (Bacillus cereus) e MT5-11 (Brevibacterium sp.), os quais apresentaram controle da mancha angular acima de 40%, em relacao a testemunha. Nenhum isolado reduziu a severidade da ramulose e da murcha de Verticillium em relacao a testemunha, nem apresentou efeito inibitorio direto in vitro a X. axonopodis pv. malvacearum e Colletotrichum gossypii var. cephalosporioides. Para V. dahliae, apenas o isolado L2-1 apresentou efeito inibitorio.

ATIVIDADE ANTIBACTERIANA DE EXTRATOS DE Senna alata L. Roxb. SOBRE A MANCHA BACTERIANA DO MARACUJAZEIRO

The bacterial spot, caused by Xanthomonas axonopodis pv. passiflorae, is one of the major diseases of passion fruit trees in the State of Pará, and its high incidence is favored by local climatic conditions. Extracts of medicinal plants have been used with promising results in the control of phytopathogens and, for this reason, this research evaluated the antibacterial activity of alcoholic extracts of Senna alata on the in vitro growth of X. axonopodis pv. passiflorae, and in the reduction of bacteriosis in green house conditions. The extracts were obtained from leaves and pods of S. alata. In the studies In vitro, the extracts were incorporated into 523 medium, with concentration of 1%, and then 100 μL aliquots of the bacterial suspension were plated and spread in Drigalski loop plates. The plates were incubated during 48h, at 28oC, with a completely randomized experimental design. The Colony Forming Units (CFU) were counts on the plates. In vivo, extracts with concentration of 1% were applied in passion fruit plants three days before to pathogen inoculation. In both trials, copper oxychloride was the control treatment. Senna alata leaves extract inhibited 14.94% of bacterial growth in passion fruit plants, while copper oxychloride inhibited 100%. Our studies revealed that S. alata pods extract and copper oxychloride reduced significantly the severity of the disease in passion fruit plants in 37.82% and 44.0%, respectively.