Tolerance to delay in drying of hybrid maize seeds related to parental line and temperature

This study aimed to evaluate the effect of genetic composition and arrangement between female and male parents on tolerance to delayed drying of maize seeds, evaluating the physiological quality and enzyme expression. Ears were harvested close to the stage of physiological maturity (around 35% moisture) and the genotypes were identified as line 1 (L1), line 2 (L2), the hybrid (HB - ♀L1 and ♂L2), and the reciprocal hybrid (HR - ♀L2 and ♂L1). For assessment of physiological quality, CDR (4x6x2) was used, consisting of four genotypes, six times of delay before artificial drying (10, 18, 24, 28, 32, and 40 hours), and two drying delay temperatures (42 and 48 °C). DIC (4x3) was used for enzymatic expression, consisting of four genotypes and three delay times before artificial drying (10, 24 and 40 hours) at 48 °C. Analysis of variance F (p < 0.05), Tukey’s test (p < 0.05), and analysis of polynomial regressions were performed on the data. Lineage arrangement affects seed tolerance to drying delay. Therefore, susceptible lines should not be used as female parents. The seeds of the line most susceptible (L2) to delay in drying exhibit less expression of α-amylase (α-AM).

ATIVIDADE DA ENZIMA NITRATO REDUTASE EM ARROZ DE TERRAS ALTAS SOB CONDIÇÕES DE ESTRESSE HÍDRICOS

A assimilação de nitrogênio é um processo vital que controla o crescimento e desenvolvimento da planta, garantindo bons níveis de produtividade de grãos. A enzima nitrato redutase (NR) catalisa o primeiro passo enzimático da assimilação de nitrogênio pelas plantas superiores por meio da redução do nitrato (NO3-) a nitrito (NO2-). Assim, objetivou-se estudar a atividade da enzima redutase do nitrato em genótipos de arroz de terras altas e correlacioná-la com os demais caracteres agronômicos. O experimento foi conduzido em dois ambientes distintos, com e sem irrigação suplementar. As análises de atividade enzimática foram realizadas em laboratório. Foram avaliados 20 genótipos de um experimento de VCU na safra 2014/2015. O delineamento experimental foi em blocos casualizados com três repetições. Foi obtida a quantidade de nitrito liberado pelos tecidos vegetais na solução de incubação (µmoles NO2- gmf -1 h-1) em sete coletas realizadas aos 7, 14, 21, 28, 45, 75 e 100 dias após emergência (DAE), sempre no período da manhã, em todas as parcelas. Diante dos resultados, observou-se que a atividade da enzima NR, na cultura do arroz, é dependente do genótipo, do período de desenvolvimento vegetal e das condições ambientais, sendo de maior expressão no início do ciclo da cultura e em ambientes sem a ocorrência de estresse hídrico. A atividade da enzima RN não deve ser utilizada isoladamente para seleção indireta no caráter produtividade na cultura do arroz de terras altas, é necessário avaliar outras características que complementem à seleção.Palavras-chave: Oryza sativa; nitrogênio; melhoramento de plantas; expressão enzimática. ACTIVITY OF THE NITRATE REDUCTASE ENZYME IN UPLAND RICE UNDER WATER STRESS CONDITIONS ABSTRACT:Nitrogen uptake is a vital process that controls plant growth and development, ensuring great grain yield levels. The enzyme nitrate reductase (NR) catalyzes the first enzymatic step of nitrogen uptake by higher plants by reducing nitrate (NO3-) to nitrite (NO2-). Thus, the objective was to study the activity of nitrate reductase enzyme in upland rice genotypes and to correlate it with other agronomic traits. The experiment was conducted in two distinct environments, with and without supplemental irrigation. The enzymatic activity assays were performed in the laboratory. Twenty genotypes of a VCU experiment in the 2014/2015 crop were evaluated. The experimental design was in randomized blocks with three replications. The amount of nitrite released by the plant tissues in the incubation solution (µmoles NO2-gmf -1 h-1) was obtained in seven collections performed at 7, 14, 21, 28, 45, 75 and 100 days after emergence (DAE). always in the mornings, in all installments. Given the results, it was observed that the activity of NR enzyme in rice culture is dependent on genotype, plant development period and environmental conditions, being more expressive at the beginning of the crop cycle and in environments without occurrence of water stress. The activity of the RN enzyme should not be used alone for indirect selection in the productivity character in the upland rice crop, it is necessary to evaluate other characteristics that complement the selection.Keywords: Oryza sativa; nitrogen; plant breeding; enzymatic expression.

HARVEST TIMES WITH CHEMICAL DESICCATION AND THE EFFECTS ON THE ENZYMATIC EXPRESSION AND PHYSIOLOGICAL QUALITY OF SOYBEAN SEEDS

ABSTRACT This study aimed to evaluate the effect of chemical desiccants and harvest times on the enzymatic expression and physiological quality of soybean seeds. The experiment was carried out in a randomized block design with four replications, in a factorial scheme (4 × 3 + 1) with four desiccants (paraquat - 2 L ha-1, ammonium glufosinate - 2 L ha-1, diquat - 1.5 L ha-1, and saflufenacil - 40 g ha-1). These were applied at the phenological stage R7.1 (beginning of leaf yellowing) and at three harvest times (0, 14, and 28 days after the phenological stage R8). There was also a control treatment (no desiccant, harvested at R8). The physiological quality of soybean seeds and the enzymatic expressions of malate dehydrogenase, alcohol dehydrogenase, esterase, isocitrate lyase, and superoxide dismutase were evaluated in laboratory tests. Seeds harvested at the R8 + 14 stage led to the highest losses in seed quality. However, the 50 mm rainfall also affected seed deterioration. The desiccants diquat and paraquat provided the lowest and the highest damage to the seed physiological quality, respectively. The expression of the enzymes alcohol dehydrogenase, esterase, and isocitrate lyase were efficient and had an adequate correlation with the physiological quality. Malate dehydrogenase and superoxide dismutase had no satisfactory relation with the physiological tests performed with soybean seeds.