RizobactÃrias para o tratamento de sementes: seleÃÃo, eficiÃncia em campo e modos moleculares de aÃÃo. / Rhizobacteria for cotton seed treatment: screening, field efficacy and molecular modes of action

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

Rhizobacteria may act on eradication of seed-associated pathogens and plant protection against biotic and abiotic stresses. The present work aimed to select rhizobacteria to control cotton diseases and assess the molecular modes of action involved. A total of 368 rhizobacteria were tested for the controlo f damping-off and bacterial blight by treating infected seeds, respectively with Colletotrichum gossypii var. cephalosporioides and Xanthomonas axonopodis pv. malvacearum. The strains Bacillus subtilis UFLA285 and Paenibacillus lentimorbus MEN2 when tested for damping-off control assured germination 51% higher than the inoculated control and also controlled bacterial blight by up to 76%. In the field, strains when combined increased germination in two consecutive seasons, a result similar or higher to the fungicide control. UFLA285 also controlled damping-off caused by Rhizoctonia solani AG4 and significatively induced the expression of the ethylene receptor protein and peroxidase, in root and stem. Through microarray analysis, 246 genes had changed regulation, among which those related to the jasmonate/ethylene pathway, phenylpropanoids and osmorregulation. In regard to osmorregulation, proline content and aquaporin gene expression were assessed. A proline buildup was observed in infected tissues and this was higher in treated plants. The gene coding for aquaporin was down-regulated in rhizobacteria-treated and infected tissues. The rhizobacteria treatment also assured the more rapid recovery of plants submitted to a water stress and then re-watered, results obtained from photosynthesis and shoot dry weight measurements. Finally, rhizobacteria controlled diseases in cotton and the molecular mechanisms involved could be explained by the regulation of genes involved in the protection against biotic and abiotic stresses.

ASSUNTO(S)

drought tolerance rt-pcr isr, tolerÃncia à seca, rt-pcr, pgpr fitopatologia isr pgpr

ACESSO AO ARTIGO

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