Rizobactérias no controle da mancha angular do algodoeiro

Abstract

RESUMOAvaliou-se o potencial de rizobactérias na indução de resistência do algodoeiro à Xanthomonas axonopodis pv. malvacearum. Após o isolamento das rizobactérias, foram selecionados os isolados capazes de reduzir os sintomas da mancha angular bacteriana em casa de vegetação, os quais foram aplicados espacialmente separados do patógeno desafiador. Os melhores isolados foram testados quanto à capacidade de reduzir os sintomas da ramulose e da murcha de Verticillium e de inibir diretamente os patógenos in vitro. Do total de 123 isolados de rizobactérias 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 relação à testemunha. Nenhum isolado reduziu a severidade da ramulose e da murcha de Verticillium em relação à testemunha, nem apresentou efeito inibitório direto in vitro a X. axonopodis pv. malvacearum e Colletotrichum gossypii var. cephalosporioides. Para V. dahliae, apenas o isolado L2-1 apresentou efeito inibitório. Termos para indexação:Gossypium hirsutum, Xanthomonas axonopodis pv. malvacearum, Colletotrichum gossypii var. cephalosporioides, Verticillium dahliae, resistência induzida. ABSTRACTThe potential of rhizobacteria was evaluated for resistance induction against Xanthomonas axonopodis pv. malvacearum. After isolation, the rhizobacteria were screened for the reduction of angular leaf spot severity under greenhouse conditions. They were spatially separated from the challenging pathogen. The best isolates were tested for the capacity to reduce ramulose and Verticillium wilt severity and directly inhibit pathogens in vitro. From a total of 123 rhizobacterial isolates, five were selected, L2-1 (Bacillus cereus), MT5-6 (Bacillus cereus), L2-2 (Achromobacter xylosoxidans), MT5-5 (Bacillus cereus) and MT5-11 (Brevibacterium sp.), which showed angular leaf spot control above 40% as compared to the control. The tested isolates neither reduced the severity of ramulose and verticillium wilt compared to the control nor showed in vitro direct inhibition to X. axonopodis pv. malvacearum and Colletotrichum gossypii var. cephalosporioides. For V. dahliae, only isolate L2-1 showed direct inhibition.

Antagonistic activity of rhizobacteria in the inhibition of the fungus Pseudocercospora griseola (Sacc.)

“…lycopersici, who also observed potential for mycelial growth inhibition by circle technique. Ishida et al (2008) found that rhizobacteria reduced the severity of the angular leaf spot of cotton when used in seed treatment. Several authors verified antagonistic potential of rhizobacteria with good results in inhibiting the growth of phytopathogenic fungi (Kupper et al, 2003;Furlani et al, 2007;Singh et al 2011;Konusny--Andreani et al, 2014;Vafadar et al, 2014).…”

Bacteria for Cotton Plant Protection: Disease Control, Crop Yield and Fiber Quality1

“…Trials were performed in a farm of Presidente Olegário, MG, Brazil at 987 m altitude, 18°05'21" S 46°29'16" W. The experiments started by sowing the cotton (Deltaopal cultivar) seeds in December 2008. All crop management, such as physicochemical and fertilization practices, was performed by the farmer in a conventional crop system according to technical recommendations until harvest (FREIRE, 2007;ISHIDA et al, 2008).…”