Response of sunflower and soybean to infection with Sclerotinia sclerotiorum with addition of organic amendments

Abstract

The addition of compost, green waste biochar, and wood biochar to a pathosystem consisting of Sclerotinia sclerotiorum (Lib.) de Bary and two susceptible host plants, sunflower (Helianthus annuus L.) and soybean (Glycine max L.), was investigated in a greenhouse study. Plant growth characteristics, disease incidence and the mycelial growth of S. sclerotiorum in root exudates of plants inoculated and not inoculated with this pathogen were determined. Both plants showed different responses in terms of shoot and root weight. Disease incidence in sunflower was lowest in the substrate consisting of green waste biochar and compost. The disease incidence in this substrate was approximately half that in the control treatment. In soybean, the highest disease suppression was achieved with this combined substrate too. Mycelial growth in sunflower root exudates from uninoculated plants was higher than that in sunflower plants inoculated with S. sclerotiorum. The substrate did not influence mycelial growth in root exudates. Soybean root exudates did not show this effect of the pathogen. This study proves that the addition of organic matter inputs such as biochar and compost can improve plant growth and can also have favorable effects against S. sclerotiorum infection. In addition, it is demonstrated that both the pathogen and host plant are instrumental in determining the mode of action of the supplemented organic material. The addition of the same organic material can lead to different responses in certain pathogens, such as S. sclerotiorum, depending on the host plant.