Scanning electron microscopic investigation of different types of necroses in potato tubers

SEM was used to follow some changes in potato tissue resulting from pathogen infection and differences between different types of necroses in cultivars: Irga, Kuba, Rosalind and Vineta. Irga showed superficial necrotic symptoms caused by Fusarium spp., Alternaria solani, Streptomyces scabies, Rhizoctonia spp., and Phytophthora infestans. Fungal necrosis caused strong disintegration of cell walls with cell lysis. Bacteria affected deep lesion inside phloem and starch damages. Inoculation of Kuba with PVYNTN by grafting resulted in internal point necroses with damaged of phloem tissue and storage material The Rosalind and Vineta showed external necrotic lesions after mechanical inoculation with PVYNTN.