Evaluation of the role of morphological traits in seed yield of soybean (Glycine max L.) using multivariate statistical methods

Soybean seed contains about 20% oil and 40% protein and is considered as a strategic oilseed plant. Identification of the relationship between morphological traits and seed yield and improving the traits that have strong associtation with seed yield can increase the efficiency of the soybean breeding programs for seed yield improvement.

To determine the suitable indirect selection index for seed yield in soybean, the important morphological traits were evaluated in 10 soybean cultivars in randomized complete block design with three replications and multivariate statistical methods in research farm of Sari University of Agriculture Sciences and Natural Resources, Sari, Iran, in two growing seasons (2020 and 2021).

The results showed that there was significant differences between soybean cultivars for the morphological traits which indicates considerable variation among Iranian soybean cultivars. The results also showed that cv. Telar with the highest number of branches, number of pods plant-1, number of seeds pod-1 and pods weight plant-1 had the highest seed yield (5400 kg.ha-1) in the 2020 and cv. Katol with the tallest plant height, the highest number of branches, pods weight plant-1 and the 100-seed weight had the highest seed yield in 2020 and 2021 (5200 and 7688 kg.ha-1, respectively). The results of multivariate analysis showed that among the studied traits, pods weight plant-1 and plant height directly, the number of pods plant-1 with a direct effect on the pods weight plant-1 and also the 100 seed weight with a direct effect on plant height had highly positive effects on seed yield in soybean. Furthermore, the number of pods plant-1 showed negative relationship with 100 seed weight. Moreover, the results of cluster analysis showed that cv. Telar and cv. Parto were distinguished from other cultivars for short plant height and high number of pods plant-1, cv. Katol for tall plant height and high 100-seed weight and cv. Tapur for high number of seeds pod-1.

Since pods weight plant-1, plant height, number of pods plant-1 and 100 seed weight showed high positive direct effects on seed yield, therefore, cv. Prato and cv. Telar with the highest number of pods plant-1 and cv. Katol with the tallest plant height and the highest 100 seed weight can be considered for seed yield improvement in soybean breeding programs.