Potato spindle tuber viroid (Pospiviroid; PSTVd) is a pathogen that poses a threat to potato, tomato and eggplant crops in Australia. Symptom development is dependent on the strain of the viroid in conjunction with the host species and stage of development. In potatoes, severe PSTVd strains have caused losses of up to 65% in tuber number and size. In tomatoes, losses of 40-50% in yield have been reported.
Infected tubers have pointed ends, giving them a spindle shape with a round cross-section. Infected tubers are also often smaller than healthy ones. Above ground symptoms of PSTVd infection of potato include a reduction in leaf size, then stems which develop in a more upright manner, and an increase in the length of the internodes (stem regions between the leaves). These symptoms are usually only present under high infection levels. Infection of tomato causes the foliage to become mottled, and yellow or purple, and the plants are stunted. Fruit produced from these plants is smaller, misshapen and will fail to ripen. Symptoms can be mild at first but will become more severe with each successive generation.
PSTVd symptoms can be confused with nutrient deficiency or toxicity, spray damage, insect damage or plant viruses.
Author(s):Plant Health Australia
Published:February 13, 2019
Date added:February 19, 2019