Path Analysis in Soybean Under Drought Stress and Co-inoculated With Azospirillum brasilense

Abstract

The study was carried out with the objective of verifying the effect of the bacterium Azospirillum brasilense in the behavior of the morphological characteristics of cultivars soybean submitted to drought stress. Two experiments were carried in randomized blocks with a split-split plot design, with four replications. We evaluated the cultivars TMG 132 and ANTA 82. The treatments were subjected to two irrigation depths: total irrigation (100% of crop evapotranspiration) and irrigation with drought stress (25% of crop evapotranspiration) and co-inoculated with Azospirillum brasilense and inoculated whit only Bradyrhizobium japonicum. The coefficients of the correlation between the characteristics: leaf area, plant height, root length, number of nodules, shoot dry matter, root dry matter and nodule dry matter were analyzed, as well as the effects over the productivity through the path analisys. The drought stress did not alter the correlations between the studied characteristics; however the alteration happened due to the inoculation method. The path analysis showed that the root length was the only variable that had a direct effect on soybean grain yield, and this occurred only inoculation. In the co-inoculated treatments with Azospirillum brasilense, there were greater indirect effects in grain yield due the root dry matter and shoot dry matter.