Anaerobic Soil Disinfestation Reduces Germination and Affects Colonization of Sclerotium rolfsii Sclerotia

Abstract

Growth chamber and field studies were conducted with organic amendment mixtures of carbon (C) and nitrogen (N) at C:N ratios 10:1, 20:1, 30:1, and 40:1 and amendment rates of C at 2, 4, 6, and 8 mg/g of soil (C:N ratio 30:1) to evaluate anaerobic soil disinfestation (ASD) effects on germination and colonization of Sclerotium rolfsii. In the growth chamber, sclerotial germination was reduced in all ASD treatments regardless of C:N ratio (0.6 to 8.5% germination) or amendment rate (7.5 to 46%) as compared with nonamended controls (21 to 36% and 61 to 96%, respectively). ASD treatment increased Trichoderma spp. colonization of sclerotia, with consistently higher colonization in ASD treatments with amendment rates of C at 2 or 4 mg/g of soil (>87% colonization) compared with nonamended controls (<50% colonization). In the 2014 field study, sclerotial germination was reduced by 24 to 30% in ASD treatments when compared with the nonamended control. Sclerotial colonization by Trichoderma spp. was predominant; however, other potential mycoparasites (i.e., Aspergillus spp., Fusarium spp., zygomycetes, and other fungi) were present in the field study. Amendment C:N ratios in the range of 10:1 to 40:1 were equally effective in reducing sclerotial germination and enhancing colonization by potentially beneficial mycoparasites of sclerotia.