Tuber-borne viral and mycoplasmal diseases of the potato in Bangladesh*

Indexing for viral and mycoplasma-like diseases was carried out in three local potato varieties, viz., ‘Dohazari Lal’, ‘Lal Kabari’ and ‘Phutki’, revealing that all the tubsrs tested were infected with more than one virus. Potato Virus S (PVS) and Potato Virus Y (PVY) were detected in 100% plants; more than one strain of PVY were identified; Potato Virus M (PVM) was found to be associated with 90% of the plants; and Potato Aucuba Mosaic Virus (PAMV) was present in 65% of the plants. Potato Leafroll Virus (PLRV) was assayed from one plant out of the ten plants of the ‘Dohazari Lal’ where as the other two varieties were found to be free from PLRV. All the three varieties appeard immune or free from Potato Virus X (PVX).

Mycoplasma-associated diseases (Yellows) developed in all the plants ‘Lal-Kabari’ and in some plants of ‘Dohazari Lal’ and ‘Phutki’. Some plants of the ‘Dohazari Lal’ and ‘Phutki’ in spite of the heavy infectione of PVS, PVM, PVY (Y^c, Y^N or other strains and PAMV were found to grow almost normally. But the plants infected with above-mentioned viruses when associated with Yellows diseases, were completely degenerated and seldom produced any tuber. From the symptoms, plants were diagnosed to be suffering from Marginal Flavescence (MF) and Purple Top Roll (PTR). Revitalization of local varieties for its wider adaptation to tropical conditions and its ability to yield modestly with resource poor farmers through positive selection is envisaged.