ABSTRACT The work was intended to evaluate the effect of different organic compounds originating from the mixture of agroindustrial and urban wastes, as well as their doses in the physiology and production of cowpea. The experiment was conducted under a randomized block design, in a 4 x 5 + 2 factorial arrangement, with four organic fertilizers (3 composed obtained from of sewage sludge, green coconut shell, carnauba butt; and sewage sludge biochar), five doses (20, 40, 60, 80 and 100 t ha-1) and two additional treatments (without fertilization and mineral fertilization). We evaluated the leaf gas exchange in three phenological stages and the productive aspects. Regarding the physiological variables, the compounds with carnauba butt and green coconut shell promoted the best results and throughout the crop cycle, the gas exchange decreased. The productive aspects were increased by about 60%, especially due to the treatments with organic compounds. The PCA can confirm the univariate results, with emphasis on compounds with green coconut shell and carnauba butt. The high percentage of explanation found in axis 1 (60.49%) may be associated with the fact that the gas exchange and production variables are highly responsive to fertilization. The treatment with biochar caused a reduction in both in the physiological and in the productive aspects. The compounds with carnauba tip and green coconut shell promote satisfactory results, being viable alternatives to complement chemical fertilization with an indicated dose of 300g pot-1 or 60 t ha-1. wastes cowpea design arrangement 3 ( biochar, , biochar) 20, 20 (20 40 8 10 ha1 ha ha-1 without . fertilization) cycle decreased 60% 60.49% 6049 49 (60.49% g pot1 pot pot- 6 ha1. 1. (2 ha- 60.49 604 (60.49 60.4 (60.4 60. (60. (60 (6

RESUMO A região Nordeste brasileira apresenta condições climáticas favoráveis ao desenvolvimento da floricultura; contudo, a escassez hídrica e a salinização de parte de suas fontes hídricas atuam como entrave a essa atividade. Nesse contexto, objetivou-se testar os efeitos de níveis crescentes de salinidade da água de irrigação sobre as respostas quantitativas e qualitativas das espécies ornamentais Euphorbia milii e Zamioculcas zamiifolia, sob diferentes condições de luminosidade. A pesquisa foi realizada utilizando-se delineamento experimental em blocos casualizados, em esquema de parcelas subsubdivididas, com cinco repetições. As plantas foram cultivadas em vasos de 7 L, passando por um período inicial de aclimatação durante 15 dias com água não salina para que o seu estabelecimento não fosse comprometido; após esse período, as plantas foram submetidas a níveis crescentes de salinidade na água de irrigação (0,5; 2,0; 3,5; e 5,0 dS m-1) sob quatro intensidades luminosas (pleno sol, 30%, 50% e 70% de sombreamento), durante 60 dias. As variáveis analisadas foram altura da planta, diâmetro do caule, biomassa da parte subterrânea e das partes aéreas, tolerância à salinidade e análise qualitativa. O sombreamento teve maior impacto nas variáveis qualitativas das plantas do que na tolerância à salinidade baseada em variáveis quantitativas. O ambiente com 30% de sombreamento é o mais propício para o cultivo da E. milii quando se utiliza água de baixa a moderada salinidade. O sombreamento reduz os danos diretos da radiação nas folhas de Z. zamiifolia e melhora a qualidade visual dessa espécie sob elevada salinidade.

ABSTRACT The Brazilian Northeast region has favorable climatic conditions for the development of floriculture; however, water scarcity and salinization of part of its water sources act as an obstacle to this activity. In this context, the objective was to test the effects of increasing levels of salinity in irrigation water on the quantitative and qualitative responses of ornamental species Euphorbia milii and Zamioculcas zamiifolia, under different light conditions. The study was carried out using an experimental design in randomized blocks, in a split-split-plot scheme, with five replications. The plants were grown in 7 L pots, undergoing an initial period of acclimatization for 15 days with non-saline water so that their establishment would not be compromised; after this period, the plants were subjected to increasing levels of salinity in the irrigation water (0.5; 2.0; 3.5; and 5.0 dS m-1) under four light intensities (full sun, 30%, 50% and 70% shading) for 60 days. The variables analyzed were plant height, stem diameter, belowground and shoot biomass, salinity tolerance and qualitative analysis. Shading had a greater impact on the qualitative variables of the plants than on the salinity tolerance based on quantitative variables. The environment with 30% shading is the most favorable for the cultivation of E. milii when using water with low to moderate salinity. Shading reduces direct radiation damage to Z. zamiifolia leaves and improves the visual quality of this species under high salinity.

RESUMO Feijão-caupi é uma espécie nutritiva, cultivada em várias partes do mundo, com ampla variabilidade genética que pode ser explorada no melhoramento. Este trabalho teve como objetivo identificar genótipos fenotipicamente divergentes de Vigna unguiculata (L.) Walp., sob esta perspectiva quanto as variáveis agronômicas e fisiológicas visando produção de grãos verdes. Em um experimento conduzido em Fortaleza - CE, 13 variáveis foram avaliadas em 44 genótipos provenientes do Banco Ativo de Germoplasma da Universidade Federal do Ceará. O experimento foi instalado em delineamentos de blocos aumentados, com quatro testemunhas adicionais (cultivares comerciais). Os componentes de variância genético e ambiental foram estimados por máxima verossimilhança restrita e, a partir destes, foi calculado o coeficiente de correlação intraclasse (ICC). Foi realizada análise de componentes principais, agrupamento de Tocher e análise de correlação. As variáveis mais influenciadas pela variação genética foram: produção por planta, comprimento da vagem verde, comprimento do grão verde, massa de grãos por vagem e produtividade total, com ICC > 0.5. A análise de componentes principais permitiu identificar as características fisiológicas: gs, ci, ci.ca, e agronômicas: comprimento da vagem verde, massa de grãos verdes, número de grãos por vagem e precocidade da produção, como sendo importantes na diferenciação de genótipos de feijão-caupi. Os genótipos CE: 02, 151, 165, 172, 189, 244, 986 e 1002 possuem variabilidade genética e são recomendados para uso em um programa de melhoramento genético de feijão-caupi para produção de grãos verdes.

ABSTRACT Cowpea is a nutritious species cultivated worldwide whose high genetic variability can be exploited in breeding programs. The present study aimed to identify phenotypically divergent genotypes of Vigna unguiculata (L.) Walp., from this pe rspective concerning agronomic and physiological variables aiming at green grain production. An experiment was conducted in Fortaleza – CE, to analyse 13 variables in 44 genotypes from the Active Germplasm Bank of the Federal University of Ceará. The experiment was set up in an augmented block design with four additional controls (commercial cultivars). The genetic and environmental variance components were estimated by restricted maximum likelihood, after which the intraclass correlation coefficient (ICC) was calculated. Principal components analysis, Tocher’s clustering and correlation analysis were used in the study. The variables most influenced by genetic variance were production per plant, green pod length, green grain length, grain mass per pod, and total yield, with ICC > 0.5. Principal components analysis signalled the physiological variables gs, ci, and ci.ca and the agronomic variables of green pod length, green grain mass, number of grains per pod, and earliness of production as important for differentiating between cowpea genotypes. CE genotypes 02, 151, 165, 172, 189, 244, 986, and 1002 show genetic variability, and their use is recommended in cowpea breeding programs aimed at green-grain production.

ABSTRACT The use of organic waste for the production of plant substrates is an important environmental and economic alternative. In this perspective, we performed a work in a greenhouse, with the aim of evaluating the effect of substrates from organic waste during growth, gas exchange and accumulation of mineral elements in ‘Sunrise Solo’ papaya tree seedlings. The experimental design adopted was completely randomized, with four treatments and five repetitions, with six plants in each repetition. The treatments consisted of four types of substrates, three from the composting of sewage sludge, green coconut shell and carnaubeira palm butt, and one was the Turfa Fértil® commercial. We evaluated biometric and physiological variables and accumulation of nutrients and heavy metals in papaya seedlings. The green coconut shell and carnaubeira palm butt substrates promoted superior results for growth, dry biomass, gas exchange and accumulation of nutrients, whereas the commercial substrate and sewage sludge produced seedlings of inferior quality considering all the analyzed variables.

RESUMEN El objetivo de este estudio fue evaluar el efecto de diferentes dosis (0,10, 20, 30, 40 y 50 t ha-1) de fibra de coco verde en sustrato de crecimiento sobre el desarrollo temprano y la fisiología de dos cultivares de soya (Pampeana 40RR y Pampeana 60RR). El experimento se llevó a cabo en un invernadero utilizando un diseño experimental completamente al azar en un arreglo factorial de 2x6 (dos genotipos y seis dosis) con cinco repeticiones. Cada repetición estuvo formada por una planta, totalizando 60 unidades experimentales. Se evaluaron variables biométricas (altura, número de hojas, diámetro del tallo, área foliar y masa seca) y fisiológicas (fotosíntesis, conductancia estomática, transpiración, carbono interno, eficiencia en el uso del agua y pigmentos fotosintéticos). Después de obtener los datos, a los 30 d después de la siembra, las medias fueron sometidas a análisis de varianza y, cuando fueron significativas según la prueba F, fueron sometidas a análisis de regresión y comparación de medias por la prueba de Tukey. A través del análisis de regresión, fue posible calcular la dosis mínima ideal para cada variable. Se observó un aumento en la altura de la planta, el diámetro del tallo, el número de hojas, el área foliar, la masa seca de hojas, masa seca de tallo y masa seca de raíces de alrededor de 51.10%, 31.60%, 52.83 %, 61.78%, 79.65%, 81.52%, y 6.06%, respectivamente, cuando comparamos los valores de las dosis mínimas con los puntos máximos encontrados en cada variable. En cuanto al intercambio de gases, el cultivar 60 RR fue superior al cultivar 40 RR. En conclusión, el compuesto de fibra de coco verde influyó positivamente en el crecimiento y fisiología de los cultivares, obteniendo la mejor respuesta con la dosis de 30 t ha-1.

ABSTRACT This study aimed to evaluate the effect of different doses (0, 10, 20, 30, 40, and 50 t ha-1) of green coconut fiber in growth substrate on the early development and physiology of two soybean cultivars (Pampeana 40RR and Pampeana 60RR). The experiment was carried out in a greenhouse using a completely randomized experimental design in a 2x6 factorial arrangement (two genotypes and six doses) with five replicates. Each replicate was made up of one plant, totaling 60 experimental units. Biometric variables (height, number of leaves, stem diameter, leaf area, and dry matter) and physiological variables (photosynthesis, stomatal conductance, transpiration, internal carbon, water use efficiency, and photosynthetic pigments) were evaluated. After obtaining the data 30 d after sowing, the means were subjected to an analysis of variance and, when significant for the F test, they were subjected to regression analysis and comparison of means by the Tukey's test. Through the regression analysis, the ideal minimum dose for each variable could be calculated. We observed an increase in plant height, stem diameter, number of leaves, leaf area, leaf dry mass, stem dry mass, and root dry mass of around 51.10%, 31.60%, 52.83%, 61.78%, 79.65%, 81.52%, and 6.06%, respectively, when we compared the values of the minimum doses with the maximum points found in each variable. Regarding the gas exchange, cultivar 60 RR was superior to cultivar 40 RR. In conclusion, the green coconut fiber compound had a positive influence on the growth and physiology of the cultivars, with the best response being obtained at the dose of 30 t ha-1.

RESUMO O feijão-caupi é uma das principais leguminosas cultivadas na região Nordeste, com finalidade direcionada para a produção de grãos secos ou vagens verdes. No entanto, essa região sofre com variações climáticas, sendo a seca o principal fator de estresse abiótico. Portanto, objetivou-se avaliar as características fisiológicas, morfológicas e de produção de vagens em variedades tradicionais de feijão-caupi quanto à tolerância à seca e reidratação no semiárido brasileiro. As variedades foram: Pingo de Ouro 1,2 (PO), Sempre Verde (SV) e Feijão de Moita (FM). O delineamento experimental utilizado foi o inteiramente casualizado, em esquema fatorial 3 x 2 (3 genótipos x 2 condições hídricas do solo) com 5 repetições para cada tratamento, totalizando 30 unidades experimentais. Foram avaliadas variáveis de crescimento, metabolismo do carbono e produção de vagens. Os resultados sugerem que o estresse hídrico severo afetou negativamente todos os genótipos de feijão-caupi, sendo nesses aspectos o genótipo FM o mais sensível ao déficit hídrico severo, pois, demonstrou efeitos negativos em nível morfológico e produção de vagens mais pronunciadas. No entanto, os genótipos crioulos apresentaram características fisiológicas semelhantes ao genótipo padrão de tolerância, o PO. Além disso, todos os genótipos apresentaram recuperação após a reidratação. Em termos de produção e características de vagens o genótipo PO, em geral, apresentou melhores respostas sob condição estresse.

ABSTRACT The cowpea bean is one of the main legumes grown in the Northeast region, with a purpose directed to the production of dried grains or green pods. However, this region suffers from climatic variations, with drought being the main abiotic stress factor. Therefore, the objective was to evaluate the physiological, morphological and pod production characteristics of traditional cowpea varieties in terms of drought tolerance and rehydration in the Brazilian semiarid region. The varieties were: Pingo de Ouro 1,2 (PO), Sempre Verde (SV) and Feijão de Moita (FM). The experimental design used was entirely randomized, in a 3 x 2 factorial scheme (3 genotypes x 2 soil water conditions) with 5 replicates for each treatment, totaling 30 experimental units. Growth variables, carbon metabolism, and pod production were evaluated. The results suggest that the water stress negatively affected the cowpea genotypes, especially those that had negative effects on the morphological level and pod production. In these aspects, the genotype FM was the most sensitive to the severe water stress. However, Creole genotypes showed characteristics physiology similar to the standard tolerance genotype, the PO. Also, all genotypes recovered after rehydration. In terms of pod production and characteristics, the genotype PO, in general, presented better responses under stress conditions.

RESUMO Partindo da hipótese de que menos de 10% de porosidade de aeração são suficientes para garantir o desenvolvimento das plantas, o objetivo deste estudo foi avaliar o efeito de níveis de porosidades de aeração e densidade do solo nas trocas gasosas e no crescimento em plantas de milho. O experimento foi conduzido em casa de vegetação, em blocos aleatorizados no arranjo fatorial (2 × 5): duas densidades (1.6 e 1.7 Mg m-3) e cinco porosidades de aeração (0.07, 0.08, 0.09, 0.10 e 0.12 m3 m-3), com cinco repetições. A interação entre os fatores não causou efeito nas variáveis analisadas. Houve efeito significativo da porosidade de aeração na fotossíntese, condutância estomática, índice relativo de clorofilas (SPAD), altura de plantas e produção de biomassa, com ajustes ao modelo quadrático. A maior porosidade de aeração reduziu a condutância em 11%, seguido de 7% de redução na fotossíntese e 6.4% no SPAD. Porosidades de aeração menores que 0.10 m3 m-3, não causaram expressiva redução nos valores de trocas gasosas e crescimento do milho. Na densidade do solo de 1.7 Mg m-3 a fotossíntese, SPAD, clorofila b, total e de carotenoides foram maiores, mas sem incremento na biomassa e área foliar. Conclui-se que porosidades de aeração maiores que 0.10 m3 m-3 são mais limitantes às plantas em decorrência de modificações nos atributos do solo, como a resistência à penetração e o conteúdo de água. Os maiores teores de clorofila b e carotenoides na maior densidade são repostas de aclimatação à condição de estresse.

ABSTRACT Based on the hypothesis that less than 10% aeration porosity is sufficient to ensure plant development, the objective of this study was to evaluate the effect of levels of aeration porosity and soil density on the gas exchange and growth of maize plants. The experiment was conducted in a greenhouse, in randomized blocks in a 2 × 5 factorial arrangement: two densities (1.6 and 1.7 Mg m-3) and five aeration porosities (0.07, 0.08, 0.09, 0.10 and 0.12 m3 m-3), with five replicates. The interaction between the factors did not have an effect on the analyzed variables. Aeration porosity had a significant effect on photosynthesis, stomatal conductance, relative chlorophyll index (SPAD), plant height and biomass production, whose data were fitted by quadratic models. The highest aeration porosity reduced conductance by 11%, followed by 7% reduction in photosynthesis and 6.4% in SPAD. Aeration porosities lower than 0.10 m3 m-3 did not cause significant reduction in the values of gas exchange and growth of maize. At soil density of 1.7 Mg m-3, photosynthesis, SPAD, chlorophyll b, total chlorophyll and carotenoids were higher, but with no increments in biomass and leaf area. It is concluded that aeration porosities greater than 0.10 m3 m-3 are more limiting to plants due to changes in soil attributes, such as penetration resistance and water content. The highest contents of chlorophyll b and carotenoids at the highest density are acclimatization responses to the stress condition.

Resumo Das espécies do gênero Phaseolus, a fava é a mais tolerante à seca se comparada com os feijões comuns. Apesar da sua importância, ela tem sido pouco estudada, necessitando de pesquisas aplicadas à cultura para maior compreensão dos mecanismos envolvidos na resposta ao déficit hídrico. Este estudo avalia a tolerância de quatro genótipos de fava cultivados no Ceará quanto a sua resistência ao estresse hídrico. O experimento foi realizado em um delineamento inteiramente casualizado, no esquema fatorial 4 x 3 em que o primeiro fator foi constituído pelos genótipos: ‘Branca’, ‘Mulatinha’, ‘Preta’ e ‘Coquinho Laranja’; o segundo por três regimes hídricos: irrigado, déficit moderado e déficit severo; com cinco repetições. As plantas foram conduzidas em vasos até o estádio fenológico V3 onde foram avaliados os seguintes parâmetros fisiológicos: taxa fotossintética (A), condutância estomática (gs), relação Ci/Ca, Transpiração (E), eficiência no uso da água (EUA), eficiência no uso da água intrínseca (EUA int), eficiência instantânea de carboxilação (EiC) e taxa de transferência de elétrons (ETR). Sem comprometer seu metabolismo, o genótipo Coquinho Laranja foi mais tolerante ao déficit hídrico, evidenciando maior produtividade fotossintética, associadas à alta eficiência no uso da água pelo fechamento dos seus estômatos com redução da transpiração.

Abstract Among species of the genus Phaseolus, fava is the most tolerant to drought when compared to common beans. Despite its importance, it has been little studied, requiring applied research to the culture for a better understanding of the mechanisms involved in the response to the water deficit. This study evaluates the tolerance of four fava genotypes grown in Ceará on their resistance to water stress. The experiment was carried out in a completely randomized design, in the 4 x 3 factorial scheme in which the first factor was constituted by the cultivars: ‘Branca’, ‘Mulatinha’, ‘Preta’ and ‘Coquinho Laranja’; the second by three water regimes: irrigated, moderate deficit and severe deficit; with five replicates. (A), stomatal conductance (gs), Ci / Ca ratio, Transpiration (E), water use efficiency, efficiency in the use of intrinsic water (USA int), instantaneous carboxylation efficiency (EiC) and electron transfer rate (ETR). Without compromising its metabolism, the genotype Coquinho Laranja was more tolerant to the water deficit, evidencing higher photosynthetic productivity, associated with the high efficiency in the use of water by the closure of its stomata with reduction of transpiration.

ABSTRACT Intercropping is a method of growing plants that assists in rational use of natural resources. Based on this concept, the aim of this study was to evaluate the response of collard green and radish ‘Cometo’ crops in monoculture and in intercropping under different spatial arrangements through physical production indicators (technical coefficients). The study was conducted in plant beds in a randomized block design (RBD) with 5 treatments and 4 replications. The treatments involved growing the two crops separately and intercropped under different spatial arrangements: (1:2) one row of radish ‘Cometo’ between two rows of collard green; (2:2) two rows of radish ‘Cometo’ between two rows of collard green; and (3:2) three rows of radish ‘Cometo’ between two rows of collard green. The spatial arrangements adopted did not affect the growth and development of radish ‘Cometo’ and of collard green, and all the arrangements used exhibited high land use efficiency, especially the 3:2 arrangement, which provided the greatest land use efficiency, at 1.69.

RESUMO É notório que a agricultura nacional vem se modificando em ritmo acelerado nos últimos anos. A exigência do mercado consumidor, somada à necessidade de novos produtos, é responsável por este fato. Diante disso, a cultura da pitaia branca (Hylocereus undatus (Haw.) Britton & Rose) tem se mostrado uma alternativa viável aos produtores agrícolas da região Nordeste. Como fatores limitantes, destacam-se: as incipientes informações em relação à nutrição mineral da planta, aliada a dados referentes ao crescimento da cultura (fenologia). Assim, desenvolveu-se este trabalho visando avaliar a influência do potássio e cálcio no desenvolvimento desta cultura, bem como nas relações de trocas gasosas, na região litorânea no estado do Ceará. O delineamento estatístico foi em blocos casualizados, em arranjo fatorial 4 x 4, com 16 tratamentos e três repetições. Os tratamentos foram constituídos por doses de potássio, (0; 125; 250 e 375 mg K dm-3) e doses de cálcio, (0; 53; 106 e 159 mg Ca dm-3). As avaliações foram realizadas aos 270 dias para as determinações biométricas e 240 dias para as avaliações de trocas gasosas. Para os caracteres morfológicos, a interação nutricional que se destacou foi 250; 159 mg dm-3 (K; Ca). A fotossíntese líquida foi maior nas doses 125 mg K dm-3 e 0 mg Ca dm-3. Para as condições ambientais em que o ensaio foi realizado, as doses 250 e 159 mg dm-3 (K; Ca) foram as que se destacaram para as variáveis analisadas.

ABSTRACT Agriculture in Brazil has improved at a fast pace in recent years, given the growing demand for quality and the need for new products. In this respect, white pitaya [Hylocereus undatus (Haw.) Britton & Rose] has become a feasible alternative for Northeast farmers. The limiting factors include a small amount of data on plant mineral nutrition and crop growth (phenology). Therefore, this study goal was to evaluate the effect of different concentrations of potassium (K) and calcium (Ca) on crop development and gas exchange in white pitaya grown in the coastal region of the state of Ceará, in Brazil. Sixteen treatments with three repetitions were organized in a completely randomized block design and a 4 × 4 factorial arrangement. Treatments consisted of various concentrations of K (0; 125; 250 and 375 mg dm-3) and Ca (0, 53, 106, and 159 mg dm-3). Biometric characteristics and gas exchange were determined after 270 and 240 days of treatment, respectively. For morphometric characteristics, the most significant nutrient combination was 250 mg dm-3 of K and 159 mg dm-3 of Ca. Net photosynthesis was higher at the dose of 125 mg dm-3 of K and 0 mg dm-3 of Ca. Our results indicate that, for the environmental conditions under which the test was conducted, an optimum nutrient combination for the analyzed variables was 250 mg dm-3 K and 159 mg dm-3 Ca.

The most critical step in any proteomic study is protein extraction and sample preparation. Better solubilization increases the separation and resolution of gels, allowing identification of a higher number of proteins and more accurate quantitation of differences in gene expression. Despite the existence of published results for the optimization of proteomic analyses of soybean seeds, no comparable data are available for proteomic studies of soybean leaf tissue. In this work we have tested the effects of modification of a TCA-acetone method on the resolution of 2-DE gels of leaves and roots of soybean. Better focusing was obtained when both mercaptoethanol and dithiothreitol were used in the extraction buffer simultaneously. Increasing the number of washes of TCA precipitated protein with acetone, using a final wash with 80% ethanol and using sonication to ressuspend the pellet increased the number of detected proteins as well the resolution of the 2-DE gels. Using this approach we have constructed a soybean protein map. The major group of identified proteins corresponded to genes of unknown function. The second and third most abundant groups of proteins were composed of photosynthesis and metabolism related genes. The resulting protocol improved protein solubility and gel resolution allowing the identification of 122 soybean leaf proteins, 72 of which were not detected in other published soybean leaf 2-DE gel datasets, including a transcription factor and several signaling proteins.

Metabolomics analysis of wild type Arabidopsis thaliana plants, under control and drought stress conditions revealed several metabolic pathways that are induced under water deficit. The metabolic response to drought stress is also associated with ABA dependent and independent pathways, allowing a better understanding of the molecular mechanisms in this model plant. Through combining an in silico approach and gene expression analysis by quantitative real-time PCR, the present work aims at identifying genes of soybean metabolic pathways potentially associated with water deficit. Digital expression patterns of Arabidopsis genes, which were selected based on the basis of literature reports, were evaluated under drought stress condition by Genevestigator. Genes that showed strong induction under drought stress were selected and used as bait to identify orthologs in the soybean genome. This allowed us to select 354 genes of putative soybean orthologs of 79 Arabidopsis genes belonging to 38 distinct metabolic pathways. The expression pattern of the selected genes was verified in the subtractive libraries available in the GENOSOJA project. Subsequently, 13 genes from different metabolic pathways were selected for validation by qPCR experiments. The expression of six genes was validated in plants undergoing drought stress in both pot-based and hydroponic cultivation systems. The results suggest that the metabolic response to drought stress is conserved in Arabidopsis and soybean plants.

The study of tolerance mechanisms for drought stress in soybean is fundamental to the understanding and development of tolerant varieties. Using in silico analysis, four marker genes involved in the classical ABA-dependent and ABA-independent pathways of drought response were identified in the Glycine max genome in the present work. The expression profiles of the marker genes ERD1-like, GmaxRD20A-like, GmaxRD22-like and GmaxRD29B-like were investigated by qPCR in root samples of drought sensitive and tolerant soybean cultivars (BR 16 and Embrapa 48, respectively), submitted to water deficit conditions in hydroponic and pot-based systems. Among the four putative soybean homologs to Arabidopsis genes investigated herein, only GmaxRD29B-like was not regulated by water deficit stress. Distinct expression profiles and different induction levels were observed among the genes, as well as between the two drought-inducing systems. Our results showed contrasting gene expression responses for the GmaxRD20A-like and GmaxRD22-like genes. GmaxRD20A-like was highly induced by continuous drought acclimating conditions, whereas GmaxRD22-like responses decreased after abrupt water deprivation. GmaxERD1-like showed a different expression profile for the cultivars in each system. Conversely, GmaxRD20A-like and GmaxRD22-like genes exhibited similar expression levels in tolerant plants in both systems.