-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 São Francisco River Valley. Two experiments were set up at the irrigated perimeters of Mandacaru (Juazeiro, state of Bahia) and Bebedouro (Petrolina, state of Pernambuco). Desempenho em campo de novas cultivares de feijão-caupi inoculadas com estirpes de rizóbio eficientes na fixação de nitrogênio no Semiárido brasileiroResumo -O objetivo deste trabalho foi avaliar a contribuição de estirpes de rizóbio, eficientes na fixação de nitrogênio, sobre a produção de grãos de novas cultivares de feijão-caupi, indicadas para cultivo no Semiárido brasileiro, no Submédio do Vale do Rio São Francisco. Dois experimentos foram implantados nos perímetros irrigados de Mandacaru (Juazeiro, BA) e Bebedouro (Petrolina, PE). Os tratamentos consistiram da inoculação isolada de cinco estirpes de rizóbio -BR 3267, BR 3262, INPA 03-11B, UFLA 03-84 (Bradyrhizobium sp.) e BR 3299 T (Microvirga vignae) -, além de um tratamento com nitrogênio e de um controle sem inoculação ou aplicação de N. As seguintes cultivares de feijão-caupi foram avaliadas: BRS Pujante, BRS Tapaihum, BRS Carijó e BRS Acauã. Utilizou-se o delineamento experimental de blocos ao acaso, com quatro repetições. As plantas inoculadas apresentaram produtividade de grãos similar à observada em plantas adubadas com 80 kg ha -1 de N. As cultivares BRS Tapaihum e BRS Pujante destacaram-se quanto à produtividade e ao teor de proteínas nos grãos, quando inoculadas, o que mostra seu potencial para cultivo na região do Submédio do Vale do São Francisco.Termos para indexação: Bradyrhizobium, Microvirga vignae, Vigna unguiculata, fixação biológica de nitrogênio, inoculante.

-The objective of this work was to evaluate the effect of drought on genetic parameters and breeding values of cassava. The experiments were carried out in a completely randomized block design with three replicates, under field conditions with (WD) or without (FI) water deficit. Yield of storage roots (RoY), shoot (ShY), and starch (StY), as well as the number of roots (NR), and root dry matter content (DMC) were evaluated in 47 cassava accessions. Significant differences were observed among accessions; according to heritability, these differences had mostly a genetic nature. Heritability estimates for genotypic effects ( h g 2 ) ranged from 0.25±0.12 (NR) to 0.60±0.18 (DMC), and from 0.51±0.17 (NR) to 0.80±0.21 (RoY and StY) for WD and FI, respectively, as a consequence of greater environmental influence on WD. Selective accuracy was lower in WD, and ranged from 0.71 (NR) to 0.89 (RoY, DMC, and StY). However, genetic gains were quite high and ranged from 24.43% (DMC) to 113.41% (StY), in WD, and from 8.5% (DMC) to 75.70% (StY) in FI. These genetic parameters may be useful for defining which selection strategies, breeding methods, and experimental designs are more suitable to obtain cassava genetic gains for tolerance to drought.Index terms: Manihot esculenta, breeding, drought stress, germplasm. Parâmetros genéticos da mandioca quanto à tolerância ao deficit hídricoResumo -O objetivo deste trabalho foi avaliar o efeito do deficit hídrico sobre os parâmetros e os valores genéticos da mandioca. Os experimentos foram realizados em delineamento de blocos ao acaso com três repetições, em campo com (CD) ou sem deficit hídrico (SD). A produtividade de raízes (PR), da parte aérea (PA) e de amido (PAM), assim como o número de raízes (NR) e a massa de matéria seca das raízes (MS) foram avaliados em 47 acessos de mandioca. Observaram-se diferenças significativas entre os acessos; conforme a herdabilidade, estas diferenças foram em sua maioria de natureza genética. As estimativas de herdabilidade dos efeitos genotípicos ( h g 2 ) variaram de 0,25±0,12 (NR) a 0,60±0,18 (MS) e de 0,51±0,17 (NR) a 0,80±0,21 (PR e PAM) para CD e SD, respectivamente, em decorrência da maior influência ambiental sobre o CD. A acurácia seletiva foi menor no CD, com variação de 0,71 (NR) a 0,89 (PR, MS e PAM). No entanto, os ganhos genéticos foram elevados, de 24,43% (MS) a 113,41% (PAM) no CD, e de 8,5% (MS) a 75,70% (PAM) no SD. Estes parâmetros genéticos podem ser úteis para definir estratégias de seleção, métodos de melhoramento e delineamentos experimentais mais apropriados, para a obtenção de ganhos genéticos em mandioca quanto à tolerância à seca.Termos para indexação: Manihot esculenta, melhoramento, estresse hídrico, germoplasma.

No abstract

The development of cassava (Manihot esculenta Crantz) with a high yield under water-deficit conditions is one of the goal of the breeding programs. The objective of this study was to evaluate the performance and to select cassava accessions based on drought tolerance indices and productive potential under water stress. Forty-nine accessions were evaluated for five agronomic traits (plant height-PH, root yield-RoY, shoot yield-ShY, harvest index-HI; and dry matter content of roots-DMC) under full irrigation conditions and drought stress (DS). The accessions were selected based on: (i) high yield under drought conditions (HY-DS) and (ii) high drought tolerance (Dr-To) based on six different indices. Overall, water stress dramatically reduced the traits' means (RoY-72.98%, ShY-54.95%, DMC-26.15%, HI-31.05%, and PH-32.95%). Low coincidence among the top ten accessions was identified based on HY-DS and Dr-To criteria. Therefore, considering only the most important traits (RoY and ShY), five accessions (BGM0815, BGM0598, 9624-09, BGM0818, and BRS Formosa) presented high HY-DS. In contrast, to Dr-To criterion, eight and nine accessions were selected for high yield of the aerial part (ShY and PH) and roots (RoY and DMC), respectively. The mean productivity, geometric mean productivity, and drought tolerance indices were the most promising to identify genotypes with high agronomic attributes, while drought susceptibility index, susceptibility, and yield stability index were suitable to identify the most drought tolerant accessions. This set of selected accessions can be used in breeding programs aimed at high yield and drought tolerance.

Plant species that naturally occur in the brazilian Caatinga (xeric shrubland) adapt in several ways to these harsh conditions, and that can be exploited to increase crop production. among the strategic adaptations to confront low water availability, desiccation tolerance stands out. Up to now, the association of those species with beneficial soil microorganisms is not well understood. The aim of this study was to characterize Tripogon spicatus diazotrophic bacterial isolates from the Caatinga biome and evaluate their ability to promote plant growth in rice. sixteen bacterial isolates were studied in regard to their taxonomic position by partial sequencing of the 16s rRna gene, putative diazotrophic capacity, in vitro

No abstract

-The objective of the present trial was to evaluate the productive and morphogenetic characteristics of buffel grass subjected to different air temperatures and CO 2 concentrations. Three cultivars of buffel grass (Biloela, Aridus and West Australian) were compared. Cultivars were grown in growth chambers at three temperatures (day/night): 26/20, 29/23, and 32/26 °C, combined with two concentrations of CO 2 : 370 and 550 μmol mol −1 . The experimental design was completely randomized, in a 3 × 3 × 2 factorial arrangement with three replications. There were interactions between buffel grass cultivars and air temperatures on leaf elongation rate (LER), leaf appearance rate (LAR), leaf lifespan (LL) and senescence rate (SR), whereas cultivars vs. carbon dioxide concentration affected forage mass (FM), root mass (RM), shoot/root ratio, LL and SR. Leaf elongation rate and SR were higher as the air temperature was raised. Increasing air temperature also promoted an increase in LAR, except for West Australian. High CO 2 concentration provided greater SR of plants, except for Biloela. Cultivar West Australian had higher FM in relation to Biloela and Aridus when the CO 2 concentration was increased to 550 μmol mol −1 . West Australian was the only cultivar that responded with more forage mass when it was exposed to higher carbon dioxide concentrations, whereas Aridus had depression in forage mass. The increase in air temperatures affects morphogenetic responses of buffel grass, accelerating its vegetative development without increasing forage mass. Elevated carbon dioxide concentration changes productive responses of buffel grass.

This study aimed to evaluate the initial development of the nodulating legumes jurema-rosa (Mimosa verrucosa Benth.) and angico [Anadenanthera colubrina (Vell.) Brenan] and the non-nodulating legumes umburana-de-cheiro [Amburana cearensis (Allemao) A.C. Smith] and caatingueira-verdadeira [Poincianella pyramidalis (Tul.) L.P. Queiroz]. Plants were grown in pots containing soil samples from six areas in Brazilian Caatinga biome region. Differences at the nodulation in plant roots were observed among the soils studied, pointing out a Vertisol covered by an introduced legume. The leaf gas exchange evaluations also showed differences among the plants grown in the different soils used as substrate mainly to angico and caatingueira-verdadeira.