Emphasis has been given on selection of micro-organism for biological control. However, in order to evaluate the biological control potential of a great number of micro-organisms in a small period of time it is necessary to develop an efficient bioassay. Seven hundred and sixty bacterial isolates from different habitats, were selected for compatibility with Rhizobium leguminosarum bv. phaseoli (SEMIA 4077 e SEMIA 4080). Among them 596 isolates were ineffective against both rhizobia. Bean seeds immersed in suspension of each one of these isolates were agitated for 5 hours at 10 o C and sowed in non-sterilized soil. The plants were kept in greenhouse. After the development of cotyledonary and primary leaves, these were removed and bioassayed for Xanthomonas axonopodis pv. phaseoli (XAP) control. In the cotyledonary leaves, it was observed that the isolate DFs093 offered 100% control, DFs041 and DFs1297 offered 90% and DFs490, DFs769, DFs831, DFs842 and DFs843 offered 80% control. In the primary leaves, the DFs482 isolated offered 100% and the DFs080, DFs348, DFs513, DFs622, DFs769, DFs842 and DFs912 offered 80% of XAP control.

ABSTRACT-Development of new technologies, aiming at increasing productivity in different crops, involves constant research on the effectiveness and application of these techniques in seed treatment. In this study, it was aimed at evaluating physiological potential of rice seeds treated with plant growth-promoting rhizobacteria (PGPR) (strains DFs185, DFs223, DFs306, DFs416), or with two dosages of the insecticide thiamethoxam. The variables assessed were: germination (G); first count of germination (FCG); cold test (CT); length of seedlings aerial parts (LAP), root system (LRS), and total length (TL); emergence speed index (ESI); emergence (E), at 14 days; and dry phytomass (DP). Treatments have had a positive effect on percentage of G, FCG and E. The strain DFs185 has promoted increase in percentage emergence, for five of the six lots assessed. The variables: LAP; LRS; TL; ESI; and DP have undergone low or none influence of treatments; and there has been no toxic effect of rhizobacteria or insecticide thiamethoxam. In the cold test, a negative effect of treatments has been detected. Seed treatment with rhizobacteria, as well as with thiamethoxam, improve quality of low quality rice seeds. The strain DFs185 is promising for treating rice seeds, once it stimulates seed germination and emergence.

RESUMO O presente trabalho teve por objetivo avaliar o efeito do tratamento térmico (calor-seco e água quente) sobre a germinação e controle de micro-organismos associados às sementes de mamoneira. No calor seco, as sementes foram submetidas às temperaturas de 70 e 75º C e seis tempos de exposições [0 (testemunha), 3, 6, 9, 12 e 15 dias]. Para água quente, as temperaturas foram de 42º C, 46º C e 50º C, e imersão por 15 e 30 minutos. Como referência de controle, fezse tratamento com carbendazim + thiram (60 g + 140 g/100 kg de sementes). Para avaliar a incidência de fungos nas sementes utilizou-se o teste de sanidade. A avaliação da germinação foi feita pelo método do rolo de papel toalha. O controle de micro-organismos mostrou-se satisfatório nos dois tratamentos térmicos, se comparados à testemunha. O calor seco, nos maiores tempos, apontou um índice de contaminação de 0,59 contra 2,58 da testemunha. A água quente, nas maiores temperaturas, mostrou um índice de contaminação de 0,9 contra 2,92 da testemunha. Foi observada relação inversa entre a sanidade das sementes e germinação, no tratamento com calor seco. Neste, a germinação das sementes ficou abaixo da testemunha. O tratamento com água quente não interferiu na germinação das sementes, que se mantiveram estatisticamente iguais à testemunha.