Soybean tolerance to drought depends on the associated Bradyrhizobium strain.

We evaluated the effect of three different Bradyrhizobium strains inoculated in two soybean genotypes (R01-581F, drought-tolerant, and NA5858RR, drought-sensitive) submitted to drought in two trials conducted simultaneously under greenhouse. The strains (SEMIA 587, SEMIA 5019 (both B. elkanii), and SEMIA 5080 (B. diazoefficiens)) were inoculated individually in each genotype and then submitted to water restriction (or kept well-watered, control) between 45 and 62 days after emergence. No deep changes in plant physiological variables were observed under the moderate water restriction imposed during the first 10 days. Nevertheless, photosynthesis and transpiration decreased after the severe water restriction imposed for further 7 days. Water restriction reduced growth (- 30%) and the number of nodules (- 47% and - 58% for R01-581F and NA5858RR, respectively) of both genotypes, with a negative effect on N-metabolism. The genotype R01-581F inoculated with SEMIA 5019 strain had higher photosynthetic rates compared with NA5858RR, regardless of the Bradyrhizobium strain. On average, R01-581F showed better performance under drought than NA5858RR, with higher number of nodules (51 vs. 38 nodules per plant, respectively) and less accumulation of ureides in petioles (15 µmol g-1 vs. 34 µmol g-1, respectively). Moreover, plants inoculated with SEMIA 5080 had higher glutamine synthetase activity under severe water restriction, especially in the drought-tolerant R01-518F, suggesting maintenance of N metabolism under drought. The Bradyrhizobium strain affects the host plant responses to drought in which the strain SEMIA 5080 improves the drought tolerance of R01-518F genotype.

Adaptabilidade e estabilidade de genótipos de girassol nos estados do Rio Grande do Sul e Paraná / Adaptability and stability of sunflower genotypes from the States of Rio Grande do Sul and Paraná

Neste trabalho, objetivou-se estudar a adaptabilidade e estabilidade de genótipos de girassol nos Estados do Rio Grande do Sul e Paraná, quanto a rendimento de grãos e de óleo. Os dados analisados foram obtidos da Rede de Ensaios de Avaliação de Genótipos de Girassol, coordenada pela Embrapa Soja, entre 2003 e 2007. Os ensaios foram conduzidos em delineamento de blocos ao acaso, com quatro repetições. Os métodos usados foram os de Eberhart & Russel, Lin & Binns e Annicchiarico. Correlações próximas da unidade, em valores absolutos, foram obtidas entre a média geral dos genótipos e os parâmetros de adaptabilidade dos métodos de Lin & Binns e Annicchiarico. Contudo, o método de Eberhart & Russel teve a vantagem de indicar genótipos com adaptação a ambientes específicos. Nesse método, os híbridos Agrobel 959 e Helio 360 e a variedade BRSGira 02 foram considerados ideais, por apresentar bons desempenhos em rendimento de grãos, adaptabilidade geral e boa previsibilidade. Para rendimento de óleo, essas características foram encontradas nos híbridos Agrobel 959 e EXP 1441 e nas variedades BRSGira 01, BRSGira 02 e BRSGira 03.

The objective of this paper was to study the adaptability and stability of sunflower genotypes from the states of Rio Grande do Sul and Paraná, according to their grain and oil yield. The analyzed data were obtained from the Official Sunflower Trials Network, coordinated by Embrapa Soja, from the year 2003 to 2007. The experiment was carried out in randomized block design with four replicates. The Eberhart & Russel, Lin & Binns, and Annicchiarico methods were used. Correlations close to the unit in absolute values were obtained between the general average of genotypes and the adaptability parameters of Lin & Bins and Annicchiarico methods. However, the method of Eberhart & Russel had the advantage of indicating genotypes with adaptation to specific environments. According to this method, the hybrids Agrobel 959 and Helio 360, and the variety BRSGira 02 were considered ideal, for showing good performance in yield grain, general adaptability and good previsibility. For oil yield, these characteristics were found in the hybrids Agrobel 959 and EXP 1441 as well as in the varieties BRSGira 01, BRSGira 02, and BRSGira 03.