ABSTRACT Endophytic bacteria Bacillus safensis RS95 and Pseudomonas hibiscicola RS121 were evaluated for their ability to promote the growth of rice seedlings and produce indole-acetic acid (IAA) and siderophores and to solubilize phosphates. ‘Guri’ rice seeds were immersed in bacterial endophyte cell suspensions (separated and two-strain mixed), as well as in Escherichia coli DH5α, phosphate-buffered saline (PBS) and water treatments (negative controls). Seeds were sown on agar-water in Petri plates placed vertically at an angle of 65°. The ability of plant growth-promoting endophytic bacteria (PGPEB) to produce IAA and siderophores was determined by Salkowski colorimetric and chrome azurol S (CAS) assays, respectively. Mineral phosphate solubilization activity was calculated by inoculating the endophytes onto medium containing insoluble phosphate. PGPEB showed a positive effect on the growth of rice seedlings, causing a mean growth of shoots and primary-roots of 60 and 67%, respectively. Bacterial strains also showed positive traits for IAA and siderophore production, as well as phosphate-solubilization activity.

Xanthomonas oryzae pv. oryzae (Xoo) e X. oryzae pv. oryzicola (Xoc), são os agentes causais do crestamento bacteriano da folha (CBF) e da estria bacteriana da folha (EBF), respectivamente, são pragas transmitidas por sementes e sofrem restrição no comércio internacional de arroz, por estarem ausentes em muitos países e possuírem potencial de comprometer seriamente a produção de arroz. Vinte e um isolados oriundos de sementes de arroz do Uruguai e Argentina, Gram negativos, oxidase positiva, com pigmentação amarela típica do gêneroXanthomonas e positivos no ELISA para Xoo, foram caracterizados para determinar a associação destes, com X. oryzae e seus patovares. Os isolados foram caracterizados por métodos bioquímicos, biológicos e quanto à sensibilidade a antibióticos. Análises de PCR e qPCR foram realizadas para a confirmação do gênero Xanthomonas e identificação de Xoo e Xoc. A caracterização de 21 isolados de Xanthomonas sp., positivos no ELISA para Xoo, mostrou variabilidade entre os isolados e distinção de Xo.

Xanthomonas oryzae pv. oryzae (Xoo) and X. oryzae pv. oryzicola (Xoc), causal agents of bacterial leaf blight (BLB) and bacterial leaf streak (BLS), respectively, are pests transmitted by seeds and suffer restriction on international rice trade, because are absent in many countries and have potential to compromise seriously rice production. Twenty-one isolates from rice seeds from Uruguay and Argentina, Gram negative, oxidase positive, with typical yellow pigmentation of genus Xanthomonas and positive in ELISA for Xoo, were characterized to determine their association with X. oryze pathovars. Isolates were characterized by biochemical, biological and antibiogram methods. PCR and qPCR analyzes were performed to confirm genus Xanthomonas and identification of Xoo and Xoc. Characterization of 21 Xanthomonas sp. isolates positive on ELISA to Xoo, showed variability among isolates and distinction of Xo.