Influence of Substrates in the Development of Bean and in Pathogenicity of Rhizoctonia solani JG Kühn

The number of plants produced in horticultural substrates has increased over the last decade. These substrates are to have some physicochemical and phytosanitary characteristics that allow for optimal growth. Rhizoctonia solani JG Kuhn is one of the root and hypocotyl diseases that frequently develops in seedbeds causing severe economic losses worldwide. The aim of this work was to evaluate the substrates and additives used in bean plantlets and the R. solani disease severity. The use of vermiculite or peat did not affect bean germination percentage, but peat promoted the development of the aerial part and vermiculite improved the growth of the root system. R. solani reduced bean germination percentage and bean growth in both peat and vermiculite. The presence of additives (bentonite and/or cornmeal) in the substrates (vermiculite or peat) reduced bean germination and development, favouring the severity of R. solani. However, the addition of cornmeal improves bean dry weight of the aerial part. So, whenever it is necessary to add additives to the substrates to improve the installation and development of a biocontrol agent, such as Trichoderma harzianum, the mix of peat and cornmeal would improve the development of both bean and biocontrol agent.