RESUMOObjetivou-se, neste trabalho, avaliar o efeito do déficit hídrico sobre as características fisiológicas e produtivas do feijão-caupi e selecionar genótipos tolerantes à seca. Avaliaram-se a condutância estomática, o potencial hídrico foliar, a temperatura das folhas e a produtividade de grãos de 20 genótipos de feijão-caupi nas condições de solo e clima de Teresina, Piauí, no ano de 2008 e se conduziram dois experimentos em delineamento de blocos ao acaso com 20 tratamentos e quatro repetições, um sob déficit hídrico durante a fase reprodutiva e outro sob irrigação plena, para fins de comparação. O déficit hídrico, que foi obtido aplicando-se aproximadamente metade da lâmina requerida pelo feijão-caupi, reduziu em 72% a condutância estomática, 62% o potencial de água nas folhas, 60% a produção de grãos e aumentou em 11,7% a temperatura foliar. Nas condições de déficit hídrico treze genótipos produziram acima da média (466 kg ha , respectivamente. Em média, a produtividade de grãos dos genótipos sob irrigação plena foi 150% superior. Palavras-chave:Vigna unguiculata(L.) Walp., potencial de água na folha, condutância estomática, temperatura foliar Tolerance to water deficit of cowpea genotypes ABSTRACT The objective of this study was to evaluate physiological and productive characteristics of cowpea under water deficit and total irrigation, under soil and climate conditions of Teresina, Piauí State, in 2008. The stomatal conductance, leaf water potential, leaf temperature and grain yield of twenty cowpea cultivars were evaluated. Two experiments were carried out in a randomized block design with 20 treatments and four replications, one under water deficit during the reproductive phase and another one under total irrigation. The water deficit was obtained applying half of the water depth required by cowpea. The water deficit reduced 72% of the stomatal conductance, 40% the leaf transpiration, 62% of the leaf water potential, 60% of the grain yield and increased 11.7% the leaf temperature. Under water deficit, 13 genotypes produced above average (466 kg ha -1 ), and BRS-Paraguaçu, Pingo-de-ouro-1-2 and Pingo-de-ouro-2 presented the best grain yield with712 kg ha , respectively. The average grain yield of the experiment under total irrigation was 150% higher.

-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 Inácio and Tracuateua-192 present sensitivity to water deficit in soil and BRS-Paraguaçu, Pingo-de-ouro-1-2 and Pingo-de-ouro-2 show behavior for drought tolerance. Key words -Vigna unguiculata. Leaf area index. Chlorophyll content.Resumo -A seleção de genótipos com tolerância à seca é essencial para a produção de alimentos no mundo, especialmente em regiões de clima árido ou com má distribuição de chuvas. Nesse contexto, o objetivo deste trabalho foi identificar genótipos com características de tolerância e sensibilidade ao estresse hídrico. Foram conduzidos dois experimentos em campo, um sob déficit hídrico durante a fase reprodutiva e outro sob irrigação plena, ambos em um delineamento de blocos ao acaso com 20 tratamentos (genótipos) e quatro repetições. O déficit hídrico foi obtido aplicando-se, aproximadamente, metade da lâmina requerida pela cultura do feijão-caupi. Foram avaliados o índice de área foliar, teor de clorofila, componentes de produção e o rendimento de grãos. O déficit hídrico reduziu em 20% o índice médio de área foliar, 16% o índice médio de clorofila, 175% o número médio de vagens por planta e em 60% a produção de grãos. Os genótipos Santo Inácio e Tracuateua-192 são sensíveis ao déficit de água no solo, enquanto o BRS-Paraguaçu, o Pingo-de-ouro-1-2 e o Pingo-de-ouro-1 são tolerantes à seca.Palavras-chave -Vigna unguiculata. Índice de área foliar. Teor de clorofila.

Water deficit is one of the most common causes of severe crop‐production losses worldwide in maize (Zea mays L.). The main goal of this study was to infer about genotype × environment interaction (G × E) and to estimate genetic correlations between drought tolerance traits in maize using factor analytic (FA) multiplicative mixed models in the context of multi‐environment trial (MET) and multi‐trait multi‐environment trial (MTMET) analyses. The traits measured were: grain yield (GY), ears per plot (EPP), anthesis‐silking interval (ASI), female flowering time (FFT), and male flowering time (MFT). Three‐hundred and eight hybrids were evaluated in a total of eight trials conducted under water‐stressed (WS) and well‐watered (WW) conditions across 2 yr and two locations in Brazil. For most of the traits (GY, ASI, and FFT), the magnitude of the genetic variances differed across WS and WW conditions. Genetic correlations between water conditions for FFT and MFT were 0.81 and 0.82, respectively, indicating that it might be unnecessary to measure these traits in both water conditions. Grain yield and EPP showed moderate to high G × E, with genetic correlations of 0.57 and 0.39 between WS and WW conditions, respectively, which suggested that gene expression was not consistent across different water regimes. Therefore, it is necessary to evaluate these traits under both water conditions. Genetic correlations between pairs of traits, in general, were higher under WS conditions compared with WW conditions. Grain yield exhibited moderate correlations with EPP (r = 0.62) and FFT (r = −0.42) under WS conditions. The FA models can be a useful tool for MET and MTMET analyses in maize breeding programs for drought tolerance.

ABSTRACT. Twenty-five cultivars of grain sorghum [Sorghum bicolor (L.) Moench] were examined under both drought stress and normal conditions in 4 experiments. In each condition, genotypes were evaluated in a factorial experiment using a randomized complete block design with 3 replications. Eight drought tolerance indices including stability tolerance index, mean productivity (MP), geometric MP, harmonic mean, stress susceptibility index, tolerance index, yield index, and yield stability index were estimated for each genotype based on grain yield under drought (Ys) and irrigated conditions (Yp). The results indicated that there were positive and significant correlations among Yp and Ys with geometric MP, MP, harmonic mean, and stability tolerance index, indicating that these factors are better predictors of Yp and Ys than tolerance index, stress susceptibility index, yield stability index, and yield index. Based on adjusted means at Yp and Ys, indices geometric MP, MP, harmonic mean, and stability tolerance index, unweighted pair group method with arithmetic mean cluster and biplot analysis, the most tolerant cultivars were '9929020', '9929034', and 'N 95B'.

EVAPOTRANSPIRAÇÃO E COEFICIENTE DE CULTIVO DO FEIJÃO-CAUPI NO VALE DO GURGUÉIA, PIAUÍ  Edson Alves Bastos1;Valber Mendes Ferreira2; Cláudio Ricardo da Silva2; Aderson Soares de Andrade Júnior11 Embrapa Meio-Norte, edson@cpamn.embrapa.br2 Universidade Federal do Piauí  1 RESUMO A determinação dos valores do coeficiente de cultivo (Kc), durante o ciclo de desenvolvimento, é fundamental para se obter as necessidades hídricas de uma cultura. O presente trabalho teve por objetivo determinar a evapotranspiração e o Kc do feijão-caupi (Vigna unguiculata L. Walp.), variedade BR-17 Gurguéia, durante os diferentes estádios de desenvolvimento, utilizando um lisímetro de pesagem eletrônico. O experimento foi conduzido no município de Alvorada do Gurguéia, localizado no Vale do Gurguéia, PI, durante o período de agosto a outubro de 2005. A evapotranspiração de referência foi estimada pelo método de Penman-Monteith com base nos dados meteorológicos obtidos por uma estação agrometeorológica automática. Os resultados mostraram que a ETc foi de 288,5 mm para todo o ciclo da cultura, correspondente a um valor médio de 4,1 mm dia-1. O estádio fenológico de maior demanda hídrica foi o reprodutivo, com 5,4 mm dia-1 e os valores de Kc foram de: 0,8, no estádio inicial;0,8 a 1,1, no estádio de crescimento;1,1 a 1,4 no estádio reprodutivo e de1,4 a 0,3 no estádio final. UNITERMOS: Lisímetro de pesagem, manejo de irrigação, consumo hídrico, Kc, Vigna unguiculata.  BASTOS, E.B.; FERREIRA, V.M.; SILVA, C. R. da; ANDRADE JÚNIOR, A.S. de. COWPEA EVAPOTRANSPIRATION AND CROP COEFFICIENT  IN THEGURGUEIAVALLEY,PIAUI STATE,BRAZIL  2 ABSTRACT The determination of crop coefficient (Kc) values is essential to obtain crop water demand throughout its development stage. The present work aimed to determine cowpea (Vigna unguiculata L. Walp. BR-17 Gurgueia variety) crop evapotranspiration (ETc) and Kc values during the crop development, using an electronic weighing lysimeter. The experiment was carried out in Alvorada do Gurgueia, located in theGurgueiaValley. The reference evapotranspiration (ETo) was estimated by Penman-Monteith method with climatic data obtained from an automatic weather station installed in the area. The results showed that the ETc was288.5 mm for the entire culture cycle, corresponding to4.1 mm day ˉ¹. The highest water demand occurred at the reproductive phonological stage (an average of5.4 mm day ˉ¹). Kc values were: 0.8 at the initial stage, 0.8 to 1.1 at the crop development stage, 1.1 to 1.4 at the reproductive stage and 1.4 to 0.3 at the end of the cycle.KEY WORDS: weighing lysimeter, irrigation management, water consumption, Kc, Vigna unguiculata.

, in a randomized block design with 36 treatments (genotypes) and four replications. The sum of irrigation depth and rainfall totaled 691.6 mm and 490.8 mm for the experiments under full irrigation (FI) and water deficit, (WD), respectively. The fraction of soil water depletion reached maximum values of 26 and 75 % for FI and WD, respectively. The traits evaluated in both experiments were: number of grains (NG m-2), number of ears per square meter (NE m-2), grain yield (GY) with 13% humidity, and the water use efficiency (WUE). Cultivation under water deficit caused reduction of 59.23% in NG m-2 ; 33.27% in NE m-2 , 59.

The objective of this work was to identify sorghum lines tolerant to water stress at post-flowering. The treatments were set as a factorial arrangement, comprised of two water regimes and 25 genotypes, during the years of 2006, 2007 and 2008. The experimental design was a randomized block, with three replications. Since the combined analysis of variance revealed significant differences among the lines, among the environments and the presence of significant genotypes x environments interaction, two univariate stability estimates (Lin & Binns and Annicchiarico) and one multivariate (AMMI) were utilized for ranking the yield stability of the genotypes. Water stress decreases significantly the yield of the genotypes. The two univariate methods presented similar results, and were complementary to AMMI, allowing the selection of tolerant and responsive lines. Lines 9929020, CMSXS 230B and N 95B were drought tolerant and stable, followed by the lines BR 008B, Tx 2737 e Tx 2908 with high yield, but intermediate stability.

-The objective of this work was to evaluate water storage in a Plinthaqualf under different straw levels during the fourth ratoon season of a sugarcane (Saccharum officinarum) crop. The study was conducted in the 2013/2014 crop season, with the cultivar SP-813250, at two soil depths (0.0-0.3 and 0.3-0.6 m), in a randomized complete block design, with five straw levels (0.0, 4.2, 9.5, 13.0, and 18.4 Mg ha ) of sugarcane straw on soil surface promotes better water retention in the soil per Mg of straw added and delays the reach of critical water storage in the soil by up to 11 days, when compared with soil without straw cover.Index terms: Saccharum officinarum, no-tillage, soil mulch, water balance. Armazenamento de água em Plintossolo Argilúvico cultivado com cana-de-açúcar sob níveis de palhadaResumo -O objetivo deste trabalho foi avaliar o armazenamento de água em um Plintossolo Argilúvico sob diferentes níveis de palhada durante o ciclo de quarta soca da cana-de-açúcar (Saccharum officinarum). O estudo foi conduzido na safra 2013/2014, com a cultivar SP-813250, em duas profundidades (0,0-0,3 e 0,3-0,6 m), em delineamento de blocos ao acaso, com cinco níveis de palhada (0,0, 4,2, 9,5, 13,0, e 18,4 Mg ha -1 ) e quatro repetições. A umidade do solo foi monitorada com reflectômetro de domínio de tempo. A palhada proporcionou ganho de até 20 Mg ha -1 de colmos e manteve o solo com maior armazenamento de água do que o sem palhada, em todos os períodos avaliados. A manutenção de até 50% (9,5 Mg ha -1 ) de palhada de canade-açúcar sobre a superfície do solo promove melhor conservação de água no solo por Mg de palha adicionada e retarda em até 11 dias o alcance do armazenamento crítico de água no solo, em comparação ao solo sem cobertura de palha.Termos para indexação: Saccharum officinarum, plantio direto, cobertura do solo, balanço hídrico.