Reinaldo L. Gomide

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.

An Automatic Data Acquisition and Control Mobile Laboratory Network for Crop Production Systems Data Management and Spatial Variability Studies in the Brazilian Center-West Region

This paper describes all tools and procedures used to structure and implement an automatic data acquisition and control mobile laboratory network for crop production systems data management and spatial variability studies in the Brazilian Center-West Region. It was set up with base in remote sensing and microprocessor techniques, microelectronic devices, sensors, controls, sampling systems, data loggers, portable microcomputers, automatic data acquisition, RF communications link, and the global positioning system (GPS), allowing for the acquisition of spatially related data during tilling, planting, and harvesting. Physical chemistries and biological characteristics of the continuous soil-water-plant-atmosphere were monitored along of the crop growth period, at field conditions, seeking the rationalization of the agricultural inputs use and the performance improvement of agricultural systems. Some results are presented.

Growth and Nutrition of Mollicute-Infected Maize

Maize bushy stunt phytoplasma (MBSP) and corn stunt spiroplasma (CSS) diseases are widespread in Brazil. The leafhopper Dalbulus maidis is the insect vector for these pathogenic mollicutes. The effects of these diseases on the development of maize plants and the possible interaction of soil water availability on these effects were evaluated in two experiments carried out on potted plants. Experiment 1 was carried out in a 2 × 4 factorial, where factor 1 corresponded to healthy and mollicute-infected plants and factor 2 to the maintenance of 40, 60, 80, and 100% of the total soil water availability. Leafhoppers collected from a field with high incidence of these diseases were used to inoculate plants with mollicutes. There were three treatments in experiment 2: healthy plants, plants infected with phytoplasma, and plants infected with spiroplasma. MBSP was predominant in experiment 1. The infected plants grew less and lowered nutrient uptake, in distinct proportions, indicating a differential effect of mollicutes on nutrient uptake independent of available soil water. Soil water availability did not significantly affect plant growth and nutrient uptake or mollicute infection. The results indicated that plants infected by mollicutes contained less protein than healthy plants. Experiment 2 showed a reduction in growth of plants infected with mollicutes and less nutrient uptake by spiroplasma-infected plants. The results showed a detrimental effect of the spiroplasma on Mg uptake. Both experiments showed more water retention by infected plants than by healthy ones. These experiments clearly demonstrated that reduced plant growth and nutrient uptake are major effects on plants infected with MBSP and CSS.

Padrões de deficiência hídrica para a cultura de milho (safra normal e safrinha) no estado de Goiás e suas conseqüencias para o melhoramento genético

Deficiencia hidrica e considerada a maior restricao na producao e estabilidade da produtividade de culturas em muitas regioes do mundo. No Estado de Goias, regiao na qual predomina a producao em sequeiro, para a cultura do milho (Zea mays L.) implantada na safra normal e na safrinha, e comum sofrer periodos de estresse por deficiencia hidrica intermitente ou terminal, que reduzem o rendimento de graos. No processo de desenvolvimento de novos hibridos e variedades cultivadas, genotipos sao selecionados em funcao de sua adaptabilidade em um determinado ambiente alvo. Assim, programas de melhoramento vegetal, com o objetivo de desenvolver hibridos e variedades cultivadas mais adaptados a um determinado ambiente, requerem informacoes sob a probabilidade de ocorrencia dos diferentes tipos de deficiencia hidrica, como tambem, suas caracteristicas, intensidade e tempo, em funcao da fase fenologica da cultura. Um modelo de simulacao de culturas foi utilizado para determinar os padroes de deficiencia hidrica no estado de Goias, considerando 12 locais e 6 diferentes datas de semeadura para a cultura do milho semeada na safra normal e na safrinha. Para a cultura do milho semeado na safra normal, a perda na produtividade decorrente do estresse por deficiencia hidrica foi menor que 50%, sendo que os tipos de deficiencia hidrica que provocam um maior impacto na produtividade iniciam-se no comeco do periodo reprodutivo. Para o milho semeado na safrinha, a perda na produtividade e superior a 50%, sendo mais comum o estresse terminal, que tem sua maior intensidade no enchimento de graos.

Sorção do herbicida imazaquin em Latossolo sob plantio direto e convencional

Abstract – The objective of this study was to evaluate the effect of spatial variation of pH and organic matter ofa Dark Red soil, under different managements, on imazaquin herbicide sorption. Soil-water sorption partitioningcoefficient (K d ) was used in surface soil samples collected at 0–15 cm layer in a 38 ha area, under central pivotirrigation and with till and no-till management. Herbicide sorption was most strongly related to soil organic mattercontent and pH, revealing greatest sorption in lower pH values with greater soil organic matter content. Thesesamples were collected at no-till management area. The pH effects on imazaquin retention occur either bycontrolling the organic matter ionization form as also its speciation. The clay content in the whole area had novariation, however, it didn’t affect the K d values. Using multivariate regression and two independent variables(soil organic matter content and pH), the prediction of herbicide sorption by soil was good (R 2 = 0.91).Index terms: imidazolinone, site-specific management, organic matter, pH, conventional-tillage.

Análise multivariada da resistência do solo à penetração sob plantio direto

In order to increase agricultural production, Brazil opted for the expansion of farming areas and the intensive use of mechanization, causing serious damage to soils. At the same time, conservation practices such as no-tillage farming are also in use. Nevertheless, soil density assessments are necessary in both situations. Practical and controversial, the methodology of penetrometry is the most utilized in such assessments. The objective of this study was to identify the vertical stratification of soil resistance to penetration. Data was collected in a Typic Hapludox under no-tillage. Samples were collected in forty points of a 50 x 50m grid. Soil resistance was evaluated in three different positions in each point: plant rows, between the plant rows, and in the rows of the tractor path. Measurements were taken using a hydraulic-electronic penetrometer. Factorial analysis with orthogonal rotation, a Multivariate Analysis technique, was used to analyze soil resistance of soil layers. Four layers were identified in the plant rows, when more superficial layers had higher relative variance. Three layers were identified in the plant rows and in rows of the tractor path, points of anthropic action; in this case, deeper layers had higher relative variance.

Evaluation of maize core collection for drought tolerance

The maize genebank (GBmaize) preserves nearly 4,000 accessions for conservation and use. The use is however restricted because the accessions do not perform as well as the elite genotypes. This problem can be reduced by pre-breeding, i.e., by extending the information on germplasm and introgressing useful alleles. Since irregular rainfall distribution and drought induce maize yield losses, drought tolerance is a main breeding target. In this study, the GBmaize accessions were evaluated for drought tolerance. Environmental factors, genotypes and the respective interactions influence the phenotypic expression. There was however no interaction genotype - irrigation level, so no accessions with different performance under the two water regimes could be identified. The performance of the following accessions was promising for a number of traits: SP154, BA166, MG099, CE002, SE025, BA154, BA194, BA085, MG076, PR053, Roxo Macapa, SE016, and AL018.

CARACTERIZAÇÃO DE ESTRESSE HÍDRICO DE DUAS LINHAGENS DE MILHO (Zea mays L.) COM SONDAS DE FLUXO DE SEIVA

A populacao e a distribuicao espacial de plantas na cultura do milho sao importantes para a interceptacao da radiacao, a qual e fundamental para o rendimento. A interceptacao da radiacao e funcao da latitude do local, do dia do ano, da hora do dia e do ângulo foliar. Nao se dispoe de metodologia para previsao da melhor populacao e distribuicao espacial de plantas em funcao da arquitetura da copa, sendo ambos, em geral, determinados por experimentacao em campo. Tambem nao se dispoe de metodologia para previsao do ângulo foliar que maximize a interceptacao da radiacao. Os objetivos do trabalho foram propor equacoes e metodologias para previsao da populacao e da distribuicao espacial de plantas em funcao da arquitetura da copa, bem como de ângulos foliares que maximizem a interceptacao da radiacao em funcao do local e do dia do ano. A metodologia proposta deve ser validada pela comparacao dos resultados de rendimento obtidos de genotipos com diferentes arquiteturas de copa e cultivados em diferentes latitudes e periodos do ano.O objetivo deste trabalho foi avaliar o efeito de genotipos de sorgo sobre a biologia do pulgao Rhopalosiphum maidis (Fitch). Os experimentos foram conduzidos na Embrapa Milho e Sorgo, em Sete Lagoas, MG. Foram testados oito genotipos de sorgo, sendo sete de reconhecida resistencia ao pulgao Schizaphis graminum (Rondani), e a cultivar comercial BRS 303. Para se obter folhas para a criacao dos pulgoes em laboratorio, foi plantada, semanalmente, no campo, uma fileira de cinco metros lineares de cada material. Os experimentos foram conduzidos durante duas geracoes do pulgao, utilizando-se, na primeira, insetos recem-nascidos, com aproximadamente uma hora de idade e oriundos da cultivar BR 304. As ninfas foram individualizadas e mantidas em secoes foliares provenientes de cada uma das oito cultivares estudadas. Como segunda geracao, utilizaram-se ninfas recem-nascidas, obtidas de progenitores criados em cada genotipo estudado na fase anterior, ou seja, individuos da segunda geracao. Em ambas as geracoes, os insetos foram mantidos em câmaras climatizadas reguladas a 25 ± 1oC, UR 70 ± 10% e fotofase de 12 horas, avaliando-se o numero de instares, periodos prereprodutivo, reprodutivo e pos-reprodutivo, ciclo total, numero de ninfas produzidas por femea e peso dos insetos aos quatro e oito dias de idade, com 15 repeticoes. O delineamento experimental foi o inteiramente casualizado, em esquema fatorial (genotipos x geracoes x repeticoes). Os genotipos TX 430 (IS x SC) e GR 1.1.1.1.1 apresentaram efeito adverso sobre a biologia do inseto, reduzindo a sobrevivencia, a capacidade reprodutiva, o periodo reprodutivo, pos-reprodutivo e o ciclo total. O genotipo BRS 303 foi o hospedeiro mais adequado, proporcionando uma elevada producao de ninfas, alta viabilidade e periodos reprodutivo, pos-reprodutivo e ciclo de vida mais longos.As doencas do milho causadas por molicutes (fitoplasma e espiroplasma) destacam-se em importância para a cultura, em consequencia da alta incidencia e dos prejuizos que causam a producao de graos. Os molicutes infectam o floema das plantas; sendo assim, podem alterar a sintese de acucares e proteinas. O objetivo deste trabalho foi verificar o efeito dos molicutes na sintese de acucares soluveis totais e de proteinas em duas cultivares de milho. O experimento foi conduzido em vasos de plastico contendo 30kg solo previamente analisado e adubado, com duas plantas por vaso. O delineamento experimental utilizado foi um fatorial 3 x 2 inteiramente casualizado, com seis repeticoes; sendo tres inoculacoes (fitoplasma, espiroplasma e sadia) e duas cultivares (Dina 766 e BR 201). Trinta dias apos a inoculacao, foram realizadas medidas de temperatura foliar, umidade relativa, resistencia estomatica e transpiracao. No estadio de grao leitoso, uma das plantas foi colhida e seccionada em tres partes, para analise de acucares soluveis totais, nutrientes e materia seca. Foi realizada uma amostragem do internodio abaixo da primeira espiga e da folha bandeira, para determinacao da atividade da peroxidase e do conteudo proteico. A planta restante foi conduzida ate o final do ciclo, quando foram avaliados: numero de espigas, peso de espigas e de graos e materia seca dos graos. A analise de variância de todas as caracteristicas avaliadas nao detectou significância na interacao cultivar x inoculacao. Alguns parâmetros mostraram significância para cultivares, para inoculacao ou para ambos. Acucares soluveis, materia seca, atividade da peroxidase e conteudo proteico foram semelhantes em ambas as cultivares e nas inoculacoes. A resistencia estomatica foi maior para Dina 766 e nas plantas inoculadas por fitoplasma. A proliferacao de espigas foi maior nas plantas inoculadas pelos molicutes que nas sadias. O peso de espigas e de graos foi maior nas plantas sadias e com fitoplasma que naquelas infectadas por espiroplasma. Concentracao de nutrientes e quantidade absorvida, em geral, foram semelhantes, excetuando P e Zn. Os molicutes nao interferiram na concentracao dos acucares soluveis e no conteudo proteico total; entretanto, os dados de produtividade sugerem uma maior susceptibilidade das cultivares ao espiroplasma.

MONITORAMENTO AUTOMÁTICO DA NECESSIDADE HÍDRICA DAS CULTURAS DO FEIJOEIRO E MILHO POR MEIO DO BALANÇO DE ENERGIA/ RAZÃO DE BOWEN

ANA KELLIANE SILVA DO NASCIMENTO2; PEDRO DANTAS FERNANDES3; JANIVAN FERNANDES SUASSUNA; ANA CRISTINA MACEDO DE OLIVEIRA; MÔNICA SHIRLEY DA SILVA SOUSA; JOSELE GLEISSIANE NOBRE AZEVEDO 1 Trabalho extraído da Dissertação do primeiro autor. 2 Pesquisadora, Instituto INOVAGRI. Rua João Carvalho 800, CEP: 60140-140, Fortaleza, CE. Fone (85) 32681597. e-mail: kelliane@inovagri.org.br 3 Prof. Doutor, Depto de Engenharia Agrícola, UFCG, Campina Grande, PB 4 Doutorando em Engenharia Agrícola. UAEAg/UFCG,PB 5 Tecnológa em Irrigação, IPU, CE

A procedure for maize genotypes discrimination to drought by chlorophyll fluorescence imaging rapid light curves

BackgroundPhotosynthesis can be roughly separated into biochemical and photochemical processes. Both are affected by drought and can be assessed by non-invasive standard methods. Gas exchange, which mainly assesses the first process, has well-defined protocols. It is considered a standard method for evaluation of plant responses to drought. Under such stress, assessment of photochemical apparatus by chlorophyll fluorescence needs improvement to become faster and reproducible, especially in growing plants under field conditions. For this, we developed a protocol based on chlorophyll fluorescence imaging, using a rapid light curve approach.ResultsAlmost all parameters obtained by rapid light curves have shown statistical differences between control and drought stressed maize plants. However, most of them were affected by induction processes, relaxation rate, and/or differences in chlorophyll content; while they all were influenced by actinic light intensity on each light step of light curve. Only the normalized parameters related to photochemical and non-photochemical quenching were strongly correlated with data obtained by gas exchange, but only from the light step in which the linear electron flow reached saturation.ConclusionsThe procedure developed in this study for discrimination of plant responses to water deficit stress proved to be as fast, efficient and reliable as the standard technique of gas exchange in order to discriminate the responses of maize genotypes to drought. However, unlike that, there is no need to perform daily and time consuming calibration routines. Moreover, plant acclimation to the dark is not required. The protocol can be applied to plants growing in both controlled conditions and full sunlight in the field. In addition, it generates parameters in a fast and accurate measurement process, which enables evaluating several plants in a short period of time.