Mosaic Virus Symptoms in Potato Crops and the Occurrence of Growth Cracking in Tubers

Infection of potato plants by viruses causing mosaic symptoms may result in a reduction in crop yield, depending on severity of symptoms and incidence. In 2004 and 2007, an investigation was undertaken to examine the relationship between plants with mosaic symptoms and the occurrence of growth cracking in daughter tubers. Samples of pairs of plants affected by mosaic symptoms and plants with no symptoms were collected from nine potato crops, of which seven were cv. Estima, containing at least 20% mosaic-affected plants. Growth cracking was more prevalent on mosaic-affected plants of cv. Estima than on plants with no symptoms. The incidence of growth cracking was much greater on plants showing mosaic symptoms caused by a mixed infection of Potato virus A and Potato virus V together than on symptomatic plants infected by either virus alone. The presence of virus in plants with no symptoms did not affect the incidence of tubers affected by cracking. In a crop of the advanced selection Blue Tzar, plants with mosaic symptoms caused by Potato virus Y ^N produced more tubers with cracking than plants with no symptoms. Growth cracking did not occur in the one sampled crop of cv. Désirée infected by Potato virus A.