Morphology and pathogenicity of Rhizoctonia solani Kühn associated with potato black scurf in Nariño (Colombia)

The objective of the research was to understand diversity Rhizoctonia solani in potato crops Nariño. Tubers with sclerotia were collected from farms municipalities Pasto, Ipiales, Tuquerres and Ospina. In a laboratory, strains grouped categories, selecting 30 for morphological pathogenic studies. an PDA medium, daily mycelia growth rate (DMGR), pigmentation, texture, pattern (GP) characteristics determined. hyphae width nuclei number also evaluated. Solanum tuberosum L. Group Phureja seedlings used pathogenicity test. Initially, 494 obtained diverse cultural characteristics, 15 two each one research. Of strains, there significant differences DMGR according Tukey test (P=0.05), 96.6% had average 16.6 mm day-1. day-old colonies cream, beige, brown salmon colors. 95% isolates formed plush mycelium GP concentric simple rings, complex scattered stellate forms. Sclerotia formation began at 6 days (average), and, days, dispersed arrangement predominated, as well peripheral, brown, beige cream Three did not produce sclerotia. mean 9.7 μm, ranged between 7.2 - 8.2, without statistical differences. Twenty-four caused 100% plant infection. results suggest isolates, associated levels or anastomosis groups (AG), that will be studied future