Obtenção de isolados de rizóbios com características agronômicas desejáveis provenientes de solos da região do Amazonas

Abstract

The majority of the Amazonian soils is acid with low concentration of nitrogen and phosphorus. The use of leguminosae-rizhobia symbiosis is an alternative for the development of a sustainable agriculture of low input. Reaserches have showed that some isolates of rhizobia, besides fixing the atmospheric N, can still solubilize phosphate, availabiliting more P for the plants, then it is necessary to develop research to select strains of rhizobia more efficient in several favorable characteristics for use by plants. This research work had as objectives, to laboratory evaluations about the tolerance to acidity and toxic Al, the capacity to solubilize calcium (P-Ca) and aluminum (P-Al) phosphates and the indole-acetic acid production (AIA). To test acidity and aluminum toxicity, Among the 100 isolates tested, 91 and 82 presented tolerance with growth scale above 3,06 at 15th days in the treatment with pH 6,5 and pH 4,5 + Al, respectively. The most limiting factor the growth of the isolates ones was acidity and the aluminum. As for phosphate solubilization of the 71 isolates, where 46 isolated solubilized P-Ca and 25 solubilized P-Al, and 19 solubilized P-Ca as well as P-Al. Among the isolates able to solubilize calcium phosphate, 46 were considered as precocious and 1 as delayers and all the isolate evaluated presented capacity to solubilize aluminum phosphate, 24 were considered as precocious and 1 as delayers, the other not shown solubilizers. For the production of aia, 38 of the 71 isolates induced growth rate of root system of cucumber greater than in non-inoculated plants with them. Among the isolates, which had the best result was the INPA R670 in time of 24h.