Strawberry lethal yellows disease
A strawberry disease, known as strawberry lethal yellows, has been observed in propagation beds in New Zealand (Kitikati district, Bay of Plenty). Affected plants are flattened to the ground, they show purpling of older leaves, reduced leaf size, yellowing of younger leaves, and plants may die. Under glasshouse conditions, plants rapidly degenerate and prematurely die. Previous electron microscopy studies had showed that phytoplasmas were found in the phloem of diseased plants. Further studies were carried out in New Zealand (PCR and sequence analysis of 16S rRNA gene) and showed that the phytoplasma found is closely related to, or identical with, the phytoplasmas associated with phormium yellow leaf disease*, Australian grapevine yellows (proposed name Candidatus Phytoplasma australiense) and papaya die-back.
* Phormium yellow leaf disease was first reported in New Zealand in 1908. It only occurs on New Zealand flax (Phormium tenax, P. cookianum) and contributed to the demise of the fibre industry based on flax. It is transmitted by a plant hopper (Oliarus atkinsoni). As this insect has a very narrow host range, it is suggested that other insect species might be involved in the spread of the phytoplasma in strawberry crops (possible candidates are Ribautiana tenerrima (bramble leafhopper), Zygina zealandica (yellow pasture leafhopper) which have been observed on strawberry).
Sources
Andersen, M.T.; Longmore, J.; Liefting, L.W.; Wood, G.A.; Sutherland, P.W.; Beck, D.L.; Forster, R.L.S. (1998) Phormium yellow leaf phytoplasma is associated with strawberry lethal yellows disease in New Zealand.
Plant Disease, 82(6), 606-609.