Control of Seedling Damping-off Disease on Sugarbeet Caused by Rhizoctonia solani AG-2-2 by Endophytic Fungi and Resistance Inducer Compounds as Seed Treatment

Seedling damping-off caused by Rhizoctonia solani is one of the most important diseases of sugar beet resulting in substantial economic losses to the producers of this crop. In this study, the biocontrol capability of 16 Trichoderma isolates and one Piriformospora indica isolate against R. solani AG-2-2 was evaluated in vitro and in vivo. Among the tested isolates, Trichoderma harzianum 65 and Trichoderma viride 60 were the most effective antagonists in vitro and could inhibit mycelia growth of the pathogen in dual culture and culture filtrate assays. However, the maximum damping-off disease control in greenhouse experiments was achieved by T. harzianum 65 with 73.6% disease control that was as effective as fungicide treatment (carboxin-thiram) and followed by P. indica with 69.8% disease control. Moreover, sugar beet seeds treatment with these fungi promoted plants growth and increased root fresh weight. In addition, the efficiency of different concentration of three resistance inducer compounds BABA, MeJA, and SA to control R. solani AG-2-2 in greenhouse was assessed. The maximum disease control was observed when seeds treated with 10 mM BABA and 1 mM MeJA, probably these compounds by induction of defence mechanisms in sugar beet have increased seedlings resistance to R. solani AG-2-2. Herein, for the first time we report control of Rhizoctonia seedling damping-off by using P. indica and resistance inducer compounds BABA, MeJA and SA.