Potato virus diseases, their diagnosis and preparation of virus-tested seed potatoes by rapid propagation

Potato is the fourth most important food crop. Yields depend to a great extent on the quality of potato "seed tubers", mainly absence of virus diseases. The main viruses that infect potatoes and cause economic damage are Potato leaf roll virus (PLRV), Potato virus Y (PVY) (including strain N-NTN), Potato virus X (PVX), Potato virus S (PVS) and Potato virus M (PVM). The persistent transmission of PLRV depends on the presence of an endosymbiont bacteria and the release of a bacterial protein into the haemolymph of the aphid. Carbohydrate transport from the leaves to the tubers in PLRV-infected potato plants is blocked due to impaired translocation from the chloroplast to the cytosol by the trios e-phosphate translocator, and the loading of sucrose into the phloem of PLRV-infected plants by the sucrose transporter protein. Rapid propagation schemes seem to be preferable for countries with warm climates for production of "potato tuber seeds". In such a scheme single node cuttings are prepared in vitro from carefully virus-tested base plants, and grown in an insect-proof greenhouse to produce plantlets or mini tubers. These are then transferred to a screen house, and the following two generations are planted in the fields, remote from other potatoes. These short cycle schemes will probably become the norm in those countries interested to build up a certified seed program from scratch.