Journal of Plant Pathology Archive

Abstract:

The effects of nutrient status, temperature and pH on mycelial growth, sclerotial production and germination of Rhizoctonia solani [anastomosis groups (AGs) 2- 1 and 3] from potato were studied on a range of artificial media including potato dextrose (PDA), malt yeast extract (MYA), water (WA) and soil extract (SEA) agar. Greatest sclerotium yields were obtained on MYA for AG 3 and PDA for AG 2-1. Sclerotium yields were significantly poorer for AG 2-1 isolates compared to AG 3 isolates tested. Sclerotium yields were significantly improved when mycelia grown on nutrient poor (WA) agar were transferred to nutrient rich (PDA) media after 4 d for AG 3 isolates, but not for AG 2-1 isolates. Optimum temperatures for mycelial growth of all isolates were between 20 and 25°C on all media tested. Mycelial growth of all isolates occurred between pH 4 and 9, with an optimum of pH 5.6. Sclerotium formation occurred between pH 4 and 8 and pH 5 and 6 for AG 3 and AG 2-1 isolates, respectively. Sclerotial germination for all AG 3 isolates was optimal between 20 and 30°C on all media tested, with a pH optimum between pH 5 and 6. In soil, AG 2-1 isolates grew significantly slower compared to AG-3. Optimum temperature for mycelial growth in soil was between 20 and 25°C, regardless of anastomosis group. Sclerotial germination in soil by AG 3 isolates occurred between 10°C and 30°C. The significance of these results on the pathogenicity of R. solani is discussed.