Diversidade e caracterização de rizóbios associados ao feijão-fava no semiárido

Abstract

The lima bean is a legume producer of edible grains with high protein value, cultivated worldwide, having in Brazil, the Northeast region as the main producer. In this region, the production is made with low use of technology, resulting in low yields. Among the technologies used to increase the production of legume, we can highlight the inoculation of seed with diazotrophic bacterias, with the objective of replace or reduce nitrogen fertilization. The aim of this study was to evaluate the diversity of rhizobia in symbiosis with the lima bean adapted to semiarid conditions. To obtain the isolated was used 02 accessions of lima bean (one of indeterminate growth and other of determinate growth) and 12 composite samples of soil from different mesoregions the states of Paraíba and Pernambuco. Plants were cultived in a protected area with transparent canvas, in design completely randomized in factorial of 12 (soil) x two (accessions) in Leonard pots adapted with plastic bottle containing 1.3 L of sand and 100 mL soil, with three replicates, for 55 days. The variables analyzed were: number of nodules (NN), fresh mass of nodules (MFN), specifies biomass of nodules (BEN), dry mass of the part aerial (MSPA) and dry mass of root (MSR). Data were analyzed using the F test and the means compared by the Scott- Knott test. Of the collected nodules were isolated bacteria and determined their morphological and physiological characteristics in culture medium, in the laboratory of Soil Microbiology of UFRPE (Recife-PE). With the characteristics of the isolates was calculated the coefficient J and was performed the grouping of the bacteria. The soil of Alagoa Grande-PB showed the highest values for NN and MFN, however when analyzing the specific biomass of nodules no detectable differences. For MSR obtained only difference between accessions. And for MSPA differences were observed for both factors, emphasizing the soil of Alagoa Grande-PB, and two soils of native vegetation, Areia-PB and Garanhuns-PE, these being a possible source of efficient strains. The grouping of the bacteria showed that accession of growth determined formed 13 groups, while the other accession, 24. And analyzing all bacteria in one dendrogram were formed groups with bacteria of each separate accession and also united. Accessions differ in groups of rhizobia able to form symbiosis.