Effects of water potential on mycelial growth, sclerotial production, and germination of Rhizoctonia solani from potato

• Published in: Mycological research Vol. 110; no. 6; pp. 725 - 733
• Main Authors: Ritchie, Faye, McQuilken, Mark P., Bain, Ruairidh A.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.06.2006
• Subjects: Agar; Anastomosis group; Culture Media; Mycelia; mycelium; Mycelium - growth & development; Osmotic Pressure; Plant Diseases - microbiology; plant pathogenic fungi; Potato; potatoes; Rhizoctonia - growth & development; Rhizoctonia - isolation & purification; Rhizoctonia - physiology; Rhizoctonia solani; Sclerotia; Sodium Chloride - pharmacology; Soil - analysis; Solanum tuberosum; Solanum tuberosum - microbiology; spore germination; Spores, Fungal - physiology; Thanatephorus cucumeris; Water - chemistry; Water - pharmacology; Water potential; Potato; Rhizoctonia solani; Mycelia; Anastomosis group; Water potential; Sclerotia
• ISSN: 0953-7562; 1469-8102
• DOI: 10.1016/j.mycres.2006.04.008

The effects of osmotic and matric potential on mycelial growth, sclerotial production and germination of isolates of Rhizoctonia solani [anastomosis groups (AGs) 2-1 and 3] from potato were studied on potato dextrose agar (PDA) adjusted osmotically with sodium chloride, potassium chloride, glycerol, and matrically with polyethylene glycol (PEG) 6000. All isolates from AGs 2-1 and AG-3 exhibited fastest mycelial growth on unamended PDA (−0.4 MPa), and growth generally declined with decreasing osmotic and matric potentials. Growth ceased between −3.5 and −4.0 MPa on osmotically adjusted media, and at −2.0 MPa on matrically adjusted media, with slight differences between isolates and osmotica. Sclerotium yield declined with decreasing osmotic potential, and formation by AG 2-1 and AG-3 isolates ceased between −1.5 and −3.0 MPa and −2.5 and −3.5 MPa, respectively. On matrically adjusted media, sclerotial formation by AG 2-1 isolates ceased at −0.8 MPa, whereas formation by AG-3 isolates ceased at the lower matric potential of −1.5 MPa. Sclerotial germination also declined with decreasing osmotic and matric potential, with total inhibition occurring over the range −3.0 to −4.0 MPa on osmotically adjusted media, and at −2.0 MPa on matrically adjusted media. In soil, mycelial growth and sclerotial germination of AG-3 isolates declined with decreasing total water potential, with a minimum potential of −6.3 MPa permitting both growth and germination. The relevance of these results to the behaviour of R. solani AGs in soil and their pathogenicity on potato is discussed.