Biocompatibility Effect of Bradyrhizobium japonicum and Trichoderma Strains on Growth, Nodulation and Physiological Traits of Soybean (Glycine max L.) under Water Deficit Conditions

In the future, drought are expected to increase, affecting the productivity of crops sensitive to water scarcity. Through N2-fixation process, soybean is capable of achieving its nitrogen demands, however, this process is inhibited under drought stress conditions. Therefore, it is vital to find suitable solutions for the agricultural sustainability of soybean.

Under pot experiment, biocompatibility was studied between Bradyrhizobium japonicum and Trichoderma strains (Trichoderma viride, T. harzianum and T. kongii) for their ability to stimulate the growth, nodulation, N content and photosynthetic pigments of soybean plants under different irrigation intervals (every 2 days (I1), every 4 days (I2), and every 6 days (I3)). The experiment was conducted in summer 2020 with a split-plot randomized complete block design and six replicates. Among the Trichoderma strains, T. harzianum was the most tolerant to growth and auxin production in the maximum 25% PEG 6000 (poly ethylene glycol) concentration. Also, co-inoculation treatment (irrigation every 6 days and inoculation with B. japonicum + T. harzianum) recorded an increase rate reached to 69.4% for shoot length, 102.53% for root length, 79.06% for shoot dry weight, 103.44% for root dry weight and 178.57% for N content compared to control treatment. For physiological traits (chlorophyll a, b, carotenoids and total soluble sugar), there was a significant increase was observed when soybean plants inoculated with B. japonicum + T. harzianum treatment followed by B. japonicum + T. kongii treatment, under irrigation every 6 days condition. On the contrary, a decrease was observed in proline content for the same treatments. Thus, an adequate microbial consortium of Bradyrhizobium - Trichoderma, could represent a promising practical method for increasing the productivity of soybean especially when grown under drought conditions.