Project FAIR5 PL97-3889
HEALTH CERTIFICATION OF ROSACEOUS SPECIES
BASED ON DISEASE-INDEXING OF IN VITRO PLANTS:
VALIDATION OF DIAGNOSTICS AND DIAGNOSTIC STRATEGIES
For the pathogenic plant viruses no effective cure exists for already infected plants in the field. They cause considerable economic losses and are therefore of major concern to worldwide phytosanitary agencies. In order to tackle the problem, both detection and elimination procedures need to be improved in order to provide virus free planting material to the growers. This will - in the case of pome fruit material - guarantee an improved health status of the orchards over a considerable time period.
It is necessary here to differentiate according to the mode of transmission of the different viruses: filamentous viruses have no known vectors and are propagated only vegetatively or by grafting. Therefore plants that are free of filamentous viruses would remain healthy. Plants infected by viruses transmitted by nematodes (Nepovirus) and by viruses transmitted by pollen (Ilarviruses) need continuous control after sanitation (epidemiological survey, eradication and/or control of the vectors). The same holds true for diseases caused by phytoplasmas.
Many of the worldīs important fruit crops including apples, plums, cherries, strawberries belong to the family of Rosaceae, respectively subfamiliy Pomoideae (Malus domestica), subfamily Prunoideae (Prunus domestica, P. armeniaca), and subfamily Rosoideae (Fragaria x ananassa). Among the leading deciduous fruit crops, apples rank second only to grapes with an annual production of about 40 million tons, plums and peaches 10th with approximately 7 million tons, while cherry production reaches approximately 3 million tons, strawberry production 2 million tons and apricot production 1,5 million tons annually (FAO).
It is understood that a new directive is being prepared in accordance with Article 4 of Council Directive 92/34/EEC on the marketing of fruit plant propagating material and fruit plants intended for fruit production. A schedule for each genus and species is to be established with reference to the quality, plant health, testing procedures and methods applied, and the propagation systems used. The material has to, where applicable, comply with the relevant plant health conditions laid down in Council Directive 77/93/EEC. The pending ECīs regulations may consider the use of in vitro micropropagation to maintain prebasic material, to produce basic or certified mother plants, if proof is provided in respect to the identity of the variety.
Large scale micropropagation within one of fruit plant species is now routine but important challenges concerning evaluation of plant health await resolution before full commercial exploitation of the technology will be achieved. In the certification of fruit plants there is an urgent need for the development of rapid, reliable, sensitive and user-friendly methods for detection and identification of harmful organisms. The release of fruit cultivars to fruit growers takes several years until all known as well as diseases of unknown etiology related with a plant species are checked by indexing methods currently in use ("base line" tests are carried out in the field with woody indicators). The combination of disease elimination and disease-indexing on in vitro plants, using reliable laboratory diagnostics, would considerably reduce the efforts and contribute to savings of time, money and labour.
Tasks and expected Results
This project is coordinated by a.Univ. Prof. Dr. Margit Laimer da Câmara Machado , Institute of Applied Microbiology, University of Agricultural Sciences, Vienna, Austria.
1/12/99 by Siegfried Huss