Fungal infections of micropropagated plants at weaning: a problem exemplified by downy mildews in Rubus and Rosa

Abstract

Tissue culture has become an important technique for rapid clonal propagation of plants to provide stocks of high-health status, especially in woody perennials and fruit crops in which freedom from virus diseases and Phytophthora root rots is of paramount importance before establishment in the field, because these diseases cannot be eradicated once introduced with planting stocks [1]. Further dependency of the industries of agriculture, horticulture and forestry on tissue culture methods is to be expected as novel genes are isolated, characterised and made available for testing in different genetic backgrounds by Agrobacterium-mediated transformation techniques [2]. By these methods, as genes become available for disease resistance, salt and drought tolerance, high sugar levels or extended shelf-life in fruits, or any other traits of commercial value, there will be a demand for gene transfer technology which ultimately depends for its success on tissue culture. Rapid multiplication in vitro is necessary for evaluation of gene constructs in a wide range of transformants, rapid propagation for glasshouse and field evaluation under strict controls and eventually for sale to recoup the costs incurred in this long process. Conventional plant breeding may then benefit as genes from diverse species can be introduced to the gene pool in a crossing programme and followed in progenies by rapid molecular methods.