Monday, 6 May 2019
Name: Potato spindle tuber viroid (PSTVd)
Symptoms are highly variable depending on host, viroid strain and environmental conditions.
Many ornamental species are asymptomatically infected, such as Brugmansia suaveolens, Dahlia sp., Solanum laxum and Streptosolen jamesonii ‘Yellow’.
Mild strains cause few if any symptoms on the foliage, especially in the earlier generations. More severe strains can cause plant stunting, upright growth habit and, when viewed from above, clockwise phyllotaxy. Leaves are often a darker green than normal, rugose and distorted. Tubers are elongated (or spindle-shaped) and may have surface cracks and very prominent eyes.
Mild strains may not cause any symptoms, while severe strains cause plants to appear stunted and bunched due to shortened internodes. Leaves are small with yellowing and purpling, down curling and twisted. Flowers may abort. Fruit size is reduced and ripen erratically. More