title: Effects of water potential on mycelial growth, sclerotial production, and germination of Rhizoctonia solani from potato.
abstract: 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 (-0.4MPa), and growth generally declined with decreasing osmotic and matric potentials. Growth ceased between -3.5 and -4.0MPa on osmotically adjusted media, and at -2.0MPa 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 -3.0MPa and -2.5 and -3.5MPa, respectively. On matrically adjusted media, sclerotial formation by AG 2-1 isolates ceased at -0.8MPa, whereas formation by AG-3 isolates ceased at the lower matric potential of -1.5MPa. Sclerotial germination also declined with decreasing osmotic and matric potential, with total inhibition occurring over the range -3.0 to -4.0MPa on osmotically adjusted media, and at -2.0MPa 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 -6.3MPa 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.
authors.affiliation: Crop and Soil Research Group, Research & Development Division, The Scottish Agricultural College, Ayr Campus, Auchincruive Estate, Ayr, KA6 5HW, Scotland, UK.
authors.forename: Faye
authors.initials: F
authors.lastname: Ritchie
authors.forename: Mark P
authors.initials: MP
authors.lastname: McQuilken
authors.forename: Ruairidh A
authors.initials: RA
authors.lastname: Bain
mesh_terms: D000362:Agar; D003470:Culture Media; D025282:Mycelium / Q000254:growth & development*; D009997:Osmotic Pressure; D010935:Plant Diseases / Q000382:microbiology*; D012232:Rhizoctonia / Q000254:growth & development / Q000302:isolation & purification / Q000502:physiology*; D012965:Sodium Chloride / Q000494:pharmacology*; D012987:Soil / Q000032:analysis; D011198:Solanum tuberosum / Q000382:microbiology*; D013172:Spores, Fungal / Q000502:physiology; D014867:Water / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D003470:Culture Media; D012987:Soil; D014867:Water; D012965:Sodium Chloride; D000362:Agar