Rafaela Simão Abrahão Nóbrega

Promoção do crescimento vegetal e diversidade genética de bactérias isoladas de nódulos de feijão-caupi

O objetivo deste trabalho foi avaliar o potencial de promocao do crescimento vegetal e a diversidade genetica de bacterias isoladas de nodulos de feijao-caupi cultivado em solos do Cerrado piauiense. Avaliaram-se 26 estirpes quanto a capacidade de fixar nitrogenio em vida livre, solubilizar fosfatos inorgânicos, produzir acido-3-indolacetico (AIA) na ausencia e na presenca do aminoacido triptofano (100 mg L-1), produzir nodulos e promover o crescimento de feijao-caupi em vasos Leonard. Nenhuma estirpe fixou nitrogenio em vida livre, e 69% foram capazes de solubilizar fosfato de calcio in vitro. Na presenca de triptofano, todas as estirpes foram capazes de sintetizar o AIA em meio 79, e 80% sintetizaram o AIA em meio DYGS. Apenas quatro estirpes nodularam o feijao-caupi. O sequenciamento do gene 16S rRNA identificou as estirpes noduliferas como pertencentes aos generos Bradyrhizobium, Rhizobium, Bacillus e Paenibacillus. Entre as estirpes nao noduliferas promotoras do crescimento do feijao-caupi, estao os generos Bacillus e Paenibacillus.

Field performance of new cowpea cultivars inoculated with efficient nitrogen-fixing rhizobial strains in the Brazilian Semiarid

The objective of this work was to evaluate the contribution of efficient nitrogen-fixing rhizobial strains to grain yield of new cowpea cultivars, indicated for cultivation in the Brazilian Semiarid region, in the sub-medium of the Sao Francisco River Valley. Two experiments were set up at the irrigated perimeters of Mandacaru (Juazeiro, state of Bahia) and Bebedouro (Petrolina, state of Pernambuco). The treatments consisted of single inoculation of five rhizobial strains - BR 3267, BR 3262, INPA 03-11B, UFLA 03-84 (Bradyrhizobiumsp.), and BR 3299T(Microvirga vignae) -, besides a treatment with nitrogen and a control without inoculation or N application. The following cowpea cultivars were evaluated: BRS Pujante, BRS Tapaihum, BRS Carijo, and BRS Acaua. A randomized complete block design, with four replicates, was used. Inoculated plants showed similar grain yield to the one observed with plants fertilized with 80 kg ha-1 N. The cultivars BRS Tapaihum and BRS Pujante stood out in grain yield and protein contents when inoculated, showing their potential for cultivation in the sub-medium of the Sao Francisco River Valley.

Substrates of Mauritia flexuosa and wastewater from pig farming on growth and quality in seedlings of Acacia mangium

Sustainable alternatives should be adopted to minimise the negative environmental impacts of agricultural activities. The use of wastewater as well as organic waste, from agricultural activities or found naturally, such as the decomposed stems of the Buriti palm (Mauritia flexuosa), can be a sustainable alternative in the production of seedlings for the reforestation of areas in the process of degradation or desertification, common in the State of Piaui, Brazil. The aim of this study was to evaluate growth and quality in seedlings of Acacia mangium Willd grown in substrates with different proportions of decomposed stems of Mauritia flexuosa (DSB), and irrigated with wastewater from pig farming (WPF). The experimental design was completely randomised, arranged in a 5 x 2 factorial scheme, corresponding to five proportions of DSB and soil (v/v,% - 0:100, 20:80, 40:60, 60:40, 80:20), and two sources of irrigation water (well water and WPF), with four replications. At 100 days after sowing (DAS), the seedlings were collected to measure the variables related to growth, quality and nodulation. Height, root collar diameter, shoot dry weight, leaf area and nitrogen accumulation in the shoots were significantly influenced (p≤0.05) by the interaction between substrate and source of irrigation water. The WPF had no significant influence on the growth or quality of the Acacia mangium Willd seedlings. The best ratio between DSB substrate and soil was 46:54, considered the most suitable for seedling production in Acacia mangium Willd.

Rhizobial Diversity for Tropical Pulses and Forage and Tree Legumes in Brazil

The current information on Brazilian rhizobial diversity, concentrating especially on the microbial symbionts of tropical pulses, forage legumes, and legume trees, some of which are native to Brazil or of which Brazil is a major producer, is highlighted. These legume species are nodulated by a large number of currently known rhizobial genera, including both alpha and beta rhizobia, with widely varying nitrogen-fixing efficiencies. The rhizobial diversity is strongly affected by soil and climatic factors, as well as genetic variation among pulses. The greater diversity among rhizobia may allow the selection of more effective nitrogen-fixing strains which could be used as inexpensive inoculants to substitute/to reduce the use of nitrogen fertilizers.