Estirpes de Bradyrhizobium em simbiose com guandu-anão em casa de vegetação e no campo

Abstract

Resumo -O objetivo deste trabalho foi avaliar a eficiência simbiótica de estirpes de bactérias fixadoras de nitrogênio do gênero Bradyrhizobium com guandu-anão. Os experimentos foram conduzidos em vasos de Leonard, em vasos com solo e em campo. Foram testadas 11 estirpes em vasos de Leonard, e as que apresentaram maior eficiência em promover o crescimento do guandu-anão foram avaliadas em vasos com solo (Latossolo Vermelho-Amarelo e Cambissolo) e em campo (Latossolo Vermelho-Amarelo). Em todos os experimentos, os tratamentos foram comparados a dois controles positivos (estirpes aprovadas como inoculantes para as cultivares de guandu-anão BR 2003 e BR 2801) e a duas testemunhas sem inoculação, uma com alta concentração de N mineral, e a outra, a depender do experimento, sem N mineral (solo) ou com baixa concentração de N (vasos de Leonard). Algumas estirpes proporcionaram crescimento vegetal semelhante ou superior às estirpes-referência e às testemunhas em vaso de Leonard. Em vasos com solo, o tipo de solo influenciou os tratamentos. No campo, não houve diferença entre os tratamentos, e as estirpes nativas promoveram bom crescimento. O guandu-anão é capaz de estabelecer associação simbiótica com bactérias fixadoras de N 2 , e a estirpe UFLA 03-320 apresenta potencial para ser recomendada para a cultura junto com a estirpe BR 2801.Termos para indexação: Cajanus cajan, fixação biológica de nitrogênio, inoculante. Bradyrhizobium strains in symbiosis with dwarf pigeon pea under greenhouse and field conditionsAbstract -The objective of this work was to evaluate the symbiotic efficiency of nitrogen-fixing bacterial strains, from the genus Bradyrhizobium, with dwarf pigeon pea. The experiments were carried out in Leonard jars, in pots with soil and in the field. In Leonard jars, 11 strains were tested, and the most effective in promoting pigeon pea growth were evaluated in pots with soil (Oxisol and Cambisol) and in the field (Oxisol). In all experiments, treatments were compared to two positive controls (strains approved as inoculants for pigeon pea cultivars, BR 2003 and BR 2801) and to two controls without inoculation, one with a high concentration of mineral N, and the other, depending on the experiment, without mineral N (soil) or with low N concentration (Leonard jars). Some strains have provided plant growth similar or superior to the reference strains and to the controls in Leonard jars. In the pot experiment with soil, the soil type influenced the treatments. In the field, there was no difference among treatments, and the native strains promoted a good plant growth. Dwarf pigeon pea is able to establish a symbiotic association with nitrogen-fixing bacteria, and the strain UFLA 03-320 has the potential to be recommended for this crop together with the BR 2801 strain.

Bradyrhizobium spp. Strains in Symbiosis with Pigeon Pea cv. Fava-Larga under Greenhouse and Field Conditions

“…By testing these same treatments in dwarf pigeon pea 'Iapar 43' (Aratã), Rufini et al (2014b) observed that the strain UFLA 03-320 also stood out, as was the case in this study. Thus, since it was effective in forming symbiosis with different cultivars, it can be recommended for this species.…”

“…is a Fabaceae that benefits from BNF, obtaining most of the N required for its development from this process. This was confirmed by experiments in axenic conditions (Fernandes and Fernandes, 2000;Fernandes et al, 2003;Martins et al, 2012), in pots with soil (La Favre and Focht, 1983;Valarini and Godoy, 1994;Sanginga et al, 1996;Paz et al, 2000), or under field conditions (Espanã et al, 2006;Ahmed et al, 2014;Rufini et al, 2014b). This crop can be used for several purposes, such as for green manure (Heinrichs et al, 2005), animal feed, and human consumption (Mizubuti et al, 1995;Canniatti-Brazaca et al, 1996); for phytoremediation (Pires et al, 2006); and for recovery of degraded areas (Beltrame and Rodrigues, 2007).…”

“…It was not possible to evaluate NN and NDM since the root system of this cultivar reached a depth of nearly 0.90 m. This situation did not allow removal of nodules, as in other crops of lower architecture, or even in other varieties of the same species (Rufini et al, 2014b). Since the production period of the pigeon pea cultivar used in this study is long, it was carried out a single harvest, at 234 days after planting, when grain yield and its primary components (PP, GP, and W100) were evaluated, as well as NCG and NAG.…”

Plot size related to numbers of treatments and replications, and experimental precision in dwarf pigeon pea

“…Studies with an important cultivar of dwarf pigeon pea (IAPAR 43, Aratã) focusing on aspects related to crop rotation (Ferrari Neto et al 2012), soil compaction (Farias et al 2013), influence on soil characteristics (Cardoso et al 2014), and nitrogen fixation (Rufini et al 2014) showed promising characteristics of this pea. Dwarf pigeon pea's fresh matter of 23.80 t•ha -1 at 92 days after sowing demonstrates its potential as a cover crop (Pereira et al 2016).…”

Bradyrhizobium brasilense as an efficient soybean microsymbiont in two contrasting soils of the southwestern region of Piauí (Cerrado biome)

“…Although the use of inoculant strains has been consolidated in soybeans, it is important to consider that these microorganisms can be significantly influenced by several factors, such as climatic conditions, pH, nutrient availability, humidity, soil texture, and competition with the native communities of N 2 -fixing bacteria (rhizobia) for the occupation of infection sites in the roots of the host plants (Kaschuk et al, 2016;Castro et al, 2017;Thilakarathna & Raizada, 2017). However, there may be strains with desirable symbiotic characteristics for selection in these autochthonous communities, which can be used as inoculants of soybeans (Rufini et al, 2014;Ribeiro et al, 2015;Bromfield et al, 2017;Chibeba et al, 2017). These facts reinforce the need for recurrent selection of new efficient Bradyrhizobium strains.…”