Virus identification and development of long-term management strategies for the rhubarb industry
Rhubarb (Rhuem rhabarbarum) is an herbaceous perennial and is a cool season crop valued for its long thick, red stems. These stalks are used raw or cooked in sauces, pies and desserts and have good levels of sugars, fibre, protein, potassium, calcium, magnesium and vitamin. In Australia, rhubarb is grown as a specialty crop in all States, mostly near to the major cities. During the winter months (April to October), production centres on south-east Queensland, predominantly from the Tamborine district, and Western Australia. Summer production is centred on the southern States. Rhubarb is propagated each year by division of 2-3 year old crowns. Seed is generally not used as it does not produce true-to-type plants and produces plants of inferior quality and often with green stems. In recent years rhubarb crops in areas of Queensland and NSW have developed severe yield decline, and leaf mosaic and necrosis symptoms. This project o determined that viruses were associated with the disease symptoms o showed in a national survey that only Western Australian and Tasmanian crops were virus free o detected up to seven different viruses in rhubarb o described for the first time, worldwide, Rhubarb decline associated virus, which is closely linked to the disease syndrome o developed detection assays for all viruses o established a tissue culture and acclimatisation protocol for a number of rhubarb cultivars, including elimination of virus from infected plant lines o showed that tissue cultured plants performed as well as conventional planting material in the field o demonstrated that virus infection can lead to rapid yield decline in the field o demonstrated that re-infection of virus free plants in the field can be very rapid if care is not taken to limit this reinfection. The project has clearly shown that virus infection causing yield losses is common in rhubarb in some districts, especially Mt Tamborine (Qld), the Sydney basin (NSW) and Mornington Peninsula (Vic). Virus-free and acclimatised tissue culture plants can be produced under commercial conditions. All the elements for a grower managed clean planting material are now available.