Efficacy of Bacillus and Trichoderma on growth and anthracnose resistance in scallion

Biotic elicitors, including Trichoderma and Bacillus can improve plant growth and disease resistance. Current research evaluated the efficacy of 14 Bacillus subtilis strains, Trichoderma viride, Trichoderma harzianum, Trichoderma sp. on enhancing growth and managing anthracnose in scallion. The inhibition efficiency of Bacillus and Trichoderma on Colletotrichum growth was assessed in vitro. Besides, effective biotic treatments against anthracnose were evaluated at net house conditions. Then, defence mechanisms including endogenous SA accumulation, production of phenolic compounds, catalase, peroxidase, phenylalanine ammonia-lyase and b-1,3-glucanase were revealed. The results showed that four biotic elicitors, including B. subtilis strains CaSUT008-2, D604, SUNB1 and T. harzianum showed high antagonistic activity against in vitro growth of Colletotrichum colonies at 41-77 %. At 28 days after planting, scallion plants treated with B. subtilis strain CaSUT008-2 and SUNB1 gained stem length at 15.35-15.79 cm. These four biotic treatments had low disease severity in net-house conditions at 25.00-50.00 %. On mechanisms of anthracnose resistance, at 24 hours after inoculation (HAI), scallion plants treated with T. harzianum and B. subtilis strain CaSUT008-2 showed high content of salicylic acid at 2.17-2.20 µg/g fresh weight. At 48 HAI, scallion plants induced by B. subtilis strain SUNB1 increased phenolic compounds at 42.65 µg gallic acid/mg dry mass. Moreover, four biotic elicitors enhanced activities of catalase, peroxidase, phenylalanine ammonia-lyase and b-1,3-glucanase in treated scallion plants. This study suggests that B. subtilis strain CaSUT008-2 and SUNB1, T. harzianum stimulated growth, helped scallion plants against anthracnose disease. The combined Trichoderma-bacteria bio-inoculants may be a good strategy to develop biocontrol agent and plant growth promoter within green and sustainable production of scallion.