Anastomosis groups of Rhizoctonia solani Kuhn isolates from potato in Pakistan

Black scurf of potato, Solanum tuberosum L., caused by the fungus, Rhizoctonia solani is present in all the eight potato producing agro-ecological zones of Pakistan and R.solani anastomosis group (AG) 3 is the major cause of this disease in potato. The present investigations were conducted to study the occurrence of R. solani anastomosis groups (AGs) on this crop. During investigations. 127 R. solani isolates were recovered from potato tuber samples (sic)collected during survey of disease from year 2001 to 2004. All of them were found multinucleate. Anastomosis group determination revealed 81.89% isolates belonging to AG 3 followed by AG 5, 8.66% and AG 4, 5.5%. Occurrence of AG 3 was the highest in all the potato production zones as compared to other AGs indicating R. solani AG 3 isolates pre-dominance on potato. The maximum number of AGs, 5 each, were found in zone 2, the Punjab Province (AG1-1A, AG 3, AG 4, AG 5, and AG 9) and zone 7 comprising of parts of Northern areas of the country (AG 2-1, AG 2-2, AG 3, AG 4, and AG 5). It may be concluded from this study that several AGs are associated with black scurf disease. Anastomosis group 3 is the most common group of R. solani on potato here. Therefore, isolates of AG 3 may be used while breeding potatoes for host resistance to R. solani. This is the first report on anastomosis group determination of potato isolates of R. solani or any crop from Pakistan.