Francisco Rodrigues Freire Filho

Assessment of cowpea rhizobium diversity in Cerrado areas of northeastern Brazil

In order to contribute for the optimization of biological nitrogen fixation (BNF) associated with cowpea in Cerrado areas in the Northeast region of Brazil, this work aimed to analyze the diversity of rhizobial populations in eight areas of Cerrado, during a soybean and rice-cowpea rotation. Morphological traits (mucous production and colony morphology), genotypic analyzes (ARDRA 16S) and intrinsic resistance to antibiotics were determined for a collection of isolates captured using cowpea as a host-plant. The morphological data showed a inverse correlation (p < 0.05) between the number of legume (soybean and cowpea) crops, according to the history of each area, and rhizobium diversity, estimated by the Shannon-Weaver index. ARDRA data showed that native Cerrado areas were exclusively colonized by Bradyrhizobium elkanii, corroborating previous data. In the areas where legumes were grown, we observed two distinct situations: where soybean only were grown, a high proportion of B. japonicum was found, and where soybean and cowpea were grown, we observed more B. elkanii. The analysis of antibiotic resistance revealed five different profiles. High percentage of antibiotic resistant Bradyrhizobium spp. isolates were found in the areas cultivated for a long time, whereas the native area and areas with a few crops had fewer resistant strain. There was an inverse relationship between intrinsic antibiotic resistance and rhizobial diversity, while the last decreases as more legume crops are introduced into the area, the former increases, suggesting that the presence of legumes may provide ecological conditions to select specific rhizobium groups, which acquire competitiveness traits and become successfully established.

Tolerância ao déficit hídrico em genótipos de feijão-caupi

ABSTRACT The objective of this study was to evaluate physiological and productive characteristics of cowpea underwater deficit and total irrigation, under soil and climate conditions of Teresina, Piaui State, in 2008. Thestomatal conductance, leaf water potential, leaf temperature and grain yield of twenty cowpea cultivarswere evaluated. Two experiments were carried out in a randomized block design with 20 treatments andfour replications, one under water deficit during the reproductive phase and another one under totalirrigation. The water deficit was obtained applying half of the water depth required by cowpea. The waterdeficit reduced 72% of the stomatal conductance, 40% the leaf transpiration, 62% of the leaf waterpotential, 60% of the grain yield and increased 11.7% the leaf temperature. Under water deficit, 13genotypes produced above average (466 kg ha -1 ), and BRS-Paraguacu, Pingo-de-ouro-1-2 andPingo-de-ouro-2 presented the best grain yield with712 kg ha -1 , 667 kg ha -1 and 642 kg ha

Controle genético do comprimento do pedúnculo em feijão-caupi

The objective of this work was to investigate the genetic control of peduncle length in cowpea (Vigna unguiculata L.). A short peduncle cowpea line (TVx-5058-09C) was crossed with a long peduncle line (TE 96-282-22G). The parents and the F1, F2, RC1 (P1xF1), and RC2 (P2xF1) generations were evaluated in randomized block design with four replications. Genotypic, phenotypic, environmental, additive, and dominance variances for peduncle length were determined. Narrow and broad sense heritability, the degree of dominance, and the minimum number of genes determining peduncle length were estimated. The additive-dominant model was adequate to explain the observed variation. The additive gene effect was the most important in controlling peduncle length, which appeared to be controlled by five genes.

Adaptabilidade e estabilidade produtiva de genótipos de feijão-caupi de porte semi-ereto na Região Nordeste do Brasil

O objetivo deste trabalho foi avaliar a adaptabilidade e a estabilidade da produtividade de graos de 20 genotipos de feijao-caupi de porte semi-ereto, utilizando o modelo de efeitos aditivos principais e interacao multiplicativa. Os ensaios foram conduzidos em 16 ambientes da Regiao Nordeste do Brasil. Os efeitos de genotipos, ambientes e da interacao genotipo x ambiente, e os tres primeiros eixos da analise de componentes principais (ACP) foram significativos. Os dois primeiros eixos da ACP explicaram juntos 55,11% da soma de quadrados da interacao, correspondendo a 83,20% do padrao da interacao genotipo x ambiente. As linhagens TE-97-321G-4, EVX-92-49E e EVX-63-10E apresentaram alta adaptabilidade, mas somente a ultima foi altamente previsivel. A cultivar BRS Guariba e as linhagens EVX-92-49E e TE97-321G-4 expressam melhor potencial genetico em ambientes de alta produtividade.

Variabilidade genética em acessos de caupi analisada por meio de marcadores RAPD

The knowledge on genetic variability and the relationship among different cowpea accesses is important to maximize resource use represented by available cowpea genotypes. The objective of this work was to determine the genetic variability among 45 cowpea (Vigna unguiculata (L.) Walp.) accesses from Brazil, USA and Niger, characterized by RAPD (Random Amplified Polymorphic DNA) markers. Eight polymorphic primers were identified, comprehending a total of 48 informative bands. Based on the obtained polymorphic profiles, four major clusters were formed. Clustering was mainly influenced by the genotype origin. Most accesses from Brazilian landraces belong to just one cluster, suggesting a limited genetic basis. It is worth noting that none of the genotypes from Niger considered as possessing superior agronomical traits, such as high productivity, was present in this cluster. RAPD shows to be an efficient tool, capable of assisting cowpea genotype selection adapted to Brazilian edaphoclimatic conditions, aiming at increasing productivity and improving other desirable characteristics to meet the needs of specific regional demands.

Identification of cowpea genotypes for drought tolerance

The genotypes selection for drought tolerance is very important for world food production, principally in arid regions or sites with irregular rain distribution. The objective of this work was to identify cowpea genotypes with drought tolerance and water stress sensitivity characteristics. Two experiments were carried out with 20 treatments and four replications, one under water deficit during reproductive phase and another one under full irrigation. The water deficit was obtained applying half the water depth required by cowpea. The leaf area index, chlorophyll content, grain components and grain yield were evaluated. The water deficit reduced 20% the leaf area index, 16% the chlorophyll content, 175% the pod number per plant and 60% the grain yield. The genotypes Santo Inacio and Tracuateua-192 present sensitivity to water deficit in soil andBRS-Paraguacu, Pingo-de-ouro-1-2 and Pingo-de-ouro-2 show behavior for drought tolerance.

Variabilidade e correlações entre caracteres agronômicos em caupi (Vigna unguiculata)

O caupi ( Vigna unguiculata (L.) Walp) e um alimento basico das populacoes do Nordeste brasileiro, devendo merecer atencao com vistas a melhoria da qualidade de graos, resistencia a doencas e pragas e aumento de produtividade. Este trabalho teve por objetivo estudar a variabilidade e o potencial genetico de 28 linhagens, escolhidas apos uma selecao para cor, tamanho de graos e resistencia a viroses. A produtividade apresentou coeficiente de variacao genetico de 23,90%, e o valor agronomico, de 3,56%. O numero de vagens por pedunculo apresentou a menor estimativa do coeficiente de determinacao genetico (4,51%), e o peso de 100 graos, a maior (81,74%). O coeficiente de determinacao genetico da produtividade foi de 34,15%. As maiores estimativas de ganho genetico foram as do peso de 100 graos (21,73%) e da produtividade (19,77%). As correlacoes genotipicas foram superiores as fenotipicas e as de ambiente, destacando-se as correlacoes entre numero de ramos secundarios e produtividade (68,13%), e valor agronomico e produtividade (100%). Estes resultados mostram amplas possibilidades de selecao entre as linhagens com relacao a maioria dos caracteres estudados.

Genetic control of cowpea seed sizes

Cowpea [Vigna unguiculata (L.) Walp.] is one of the most widely adapted grain legumes in hot regions of Africa, Asia and the Americas. In the semiarid Northeast of Brazil, it is the main subsistence crop, an excellent protein source of low cost, for the poor population. The objective of this work was to estimate genetic parameters to understand the inheritance of seed sizes in cowpea. The parents P1 and P2 and the generations, F1, F2, BC1 and BC2 of the cross TVx5058-09C X Manteiguinha formed the genetic material for this study. These six generates (P1, P2, F1, F2, BC1 and BC) were evaluated in a completely randomized block-design with six replications, in Teresina - PI, Brazil, in 1998. The genetic parameters estimated were: phenotypic and total genetic variance, additive and dominance genetic components of variance and the variance attributed to the environment, heritability in the broad and narrow senses, average degree of dominance and the number of genes controlling the character. The additive - dominance model fitted the data for 100-seeds weight in as much as the midparental value and the additive effect were the more important genetic parameters for the determination of this character. The number of genes that control its expression is five. The occurrence of high values for narrow sense heritability indicates that the selection for seed size can be made in early generations.

Estimativas de parâmetros genéticos em genótipos de feijão-caupi avaliados para feijão fresco

The aim of this work was to estimate genetic parameters in traits associated with the production of fresh southern pea in 14 cowpea genotypes of purple pod and white grains. Three experiments were carried out: two under irrigation (2004 and 2005) and one in rainfed conditions (2005), at Embrapa Mid-North experimental field, in a randomized complete block design with four replications. The correlations, genetic variation and determination coefficients were estimated for the following traits: number of days for the harvest of fresh seed (NDHFS), fresh pod length (FPL), number of seeds for fresh pod (NSFP), weight of one hundred fresh seed (WHFS), fresh pod yield (FPY), fresh seed yield (FSY), fresh seed index (FSI), value of crop (VC) and plant type (PT). The genotypic correlations were superior to phenotypic and environment correlations, being distinguished the correlations between VC and FPY (100%). The genetic variation coefficient varied from 6.58% (FSI) to 31.62% (FSY), with highlight also for FPY (30.16%). All characters showed high genetic component in the expression of the character, with highlight for the FPL (98.72%). There is a high genetic component in the phenotypic expression of all the traits studied, with a high probability of genetic gains in additional cycles of selection based on phenotype. Selection of cowpea genotypes for high yield and early is easier than selection of genotypes with high yield and late in the fresh southern pea breeding.

Inter-relação entre caracteres de caupi de porte ereto e crescimento determinado

Ten characteristics were studied in 32 cowpea genotypes [Vigna unguiculata (L.)Walp.] with the objective of evaluating the association among yield and yield components. The experiment was conduced at Embrapa-Centro de Pesquisa Agropecuaria do Meio-Norte in Teresina, PI, Brazil. Acomplete random blocks design with six replications was used. The data were collected from the two central rows subtracting two hills at the extremities. Initial flowering and 100-seed weight, that presented the highest direct effect and positive correlation with grain yield, were the most important characters in the process of indirect selection to obtain an efficient correlated response on grain yield. However, selection for the characters angle insertion of the secondary branches and number of grains per pod had no significant direct influence on grain yield.