A. Nasr Esfahani, A. Mousavi Bak,
Volume 8, Issue 3 (10-2004)
Abstract
The black dot disease of potato is a fungal disease caused by Colletotrichum coccodes (syn. C. atramentarium) that produces accervuli on infected underground plant parts which appear as black dots. The disease appears at the flowering stage and develops up to the season end. The survey on black dot disease of potato in two successive years indicated that the infection percentage is 39.86 in Feraydan (Isfahan), one of the most important potato production regions in Iran. Studies on usual cropping patterns with, potato including, wheat alfa-alfa, barley and fallow showed that in terms of disease infection, one year rotation with fallow reduced the disease severity almost to half compared with control and other cropping patterns. Biological seed and soil treatment, with Trichoderma harzianum in various spores density reduced the disease in various degrees significantly and increased the potato plant growth factors including the number of stems, foliage fresh and dry weights, and also the yields in cases of spore applications, depending upon the type and application dosage. Comparative susceptibility assessments of 24 commercial potato varieties to the black dot disease indicated that the variety Desiree was the least concerned in terms of infection, followed by Scort ,Casser, Casmos, Carlita and Moren , where as Marijke, Cosima and Monalisa were highly infected in comparison to other tested verities and the rests of varieties were scored within these two ranges.
