Curl-tip disease and the potential use of Phoma aquilina as an agent of biological control of bracken

Abstract

Abstracts dehydration or plasmolysis. Protoplast structure is better preserved during cryopreservation as the rigours of dehydration are circumvented a:nd less wrinkling is apparent in frozen specimens.Holes or invaginations have been observed at the surface of many of the protoplasts. These do not appear to be interruptions of the membrane and have been observed by other workers (e.g. Burgess et al. 1977). They were not present on protoplasts that were plasmolysed, fixed, then treated with enzymes. The suggestion is advanced that these holes result from enzyme damage caused by the presence of proteases as impurities in the cell wall degrading enzymes.Protoplast regeneration Protoplasts were cultured on a modification of Moore's medium. The frequency of regeneration was generally low, the greatest percentage occurring with protoplasts isolated from crowded, slow-growing, more juvenile gametophyte cultures prolonged in the antheridial phase (possibly due to Apt production from the faster growing individuals; see Naf 1979, for review of antheridiogens). These gametophytes show parallels with the ameristic tumerous gametophytes, the protoplasts of which are capable of regeneration (Partanen et al. 1980). It seems that the regenerative capacity of Pteridium protoplasts is primarily dependent on the physiological condition of the cultures from which they are derived. A build-up of A Pt in the medium is therefore thought to be responsible for the change in cell wall composition which seems to occur as prothalli mature, as mentioned above.