Caracterização morfofisiológica de rizóbios simbiontes de guandu, feijão-de-porco, crotalária, mucuna-cinza e mucuna-preta

Abstract

Legumes (Fabaceae) have been widely used as green manure mainly because they had the ability to associate symbiotically with nitrogen fixing bacteria, bringing many benefits to improving soil quality. Thus, it becomes necessary ongoing work of selecting rhizobia, symbiotic with high efficiency and competitiveness for the different species used as green manure in different regions of the country. Present study was conducted to evaluate the symbiotic effectiveness of nitrogen fixing bacteria, the native of Cerrado soils of Mato Grosso do Sul State, associated with different species of green manure, as well as perform morphophysiological characterization of rhizobia evaluated. The study was conducted at Embrapa Western Region Agriculture in Dourados/MS. Initially proceded to phenotypic characterization of the isolates and then tests symbiotic efficiency in greenhouse conditions were conducted. 94 rhizobia in sterilized substrate (sand, vermiculite, 1:1, v:v) and those who have shown promise underwent tests in pots with soil (non-sterile). Under non-sterile conditions, five isolates were tested in hemp (Crotalaria juncea L.), and Canavalia ensiformis (L.) DC. and four other species pigeon pea [Cajanus cajan (L.) Millsp.], Mucuna aterrima (L.) (Piper & Tracy) (Holland) and four strains of symbionts Mucuna nivea (L.) DC. In both stages of selection, without inoculation treatments, with and without N fertilizer (NH4NO3) were included, as well as treatments with commercially recommended strains for production inoculants in Brazil. Isolates of native rhizobia in soils of Cerrado of Mato Grosso do Sul showed great phenotypic diversity and high potential for biological nitrogen fixation of green manure can highlight the isolates CPAO 86.1 to sun hemp, CPAO 104.3, CPAO 76.2 for jack bean, CPAO 2.1CMIGU for pigeon pea , CPAO 124.1 for Mucuna aterrima (L.) DC. and CPAO 117.1 for Mucuna nivea (L.) DC. considered promising for obtaining more effective inoculants for these species of green manure.