Mini review: The genus Porphyra sensu lato (Bangiales, Rhodophyta), its pests and defence

Abstract

The temperate genus Porphyra sensu lato has a long history of marine farming. Members of the genus are amongst the most common and economically valuable, commercially cultivated seaweeds on nets in the open sea. Species have a heteromorphic life cycle, alternating between a macroscopic blade and a microscopic, phase. The latter is an endolithic, shell-borne, filamentous thallus called the conchocelis which is cultivated separately within various bivalve shells in shallow ponds, on land. As a crop, its cultivation is accompanied by ever-increasing incidences of pests and diseases of both the blade and conchocelis phases. Serious damage is reported to be caused by the oomycete fungus Pythium (Py.) porphyrae and the chytrid Olpidiopsis spp., which have decreased the productivity of large-scale open sea farms especially in Korea and the northern coast of China. Interestingly, calcium propionate is effective combating oomycete infections. Early detection and development of resistant Porphyra strains, perhaps with some prophylactic, prebiotic treatments of low molecular weight oligoagars and selected probiotic, immune-stimulating bacteria might limit the damaging effects and economic consequences of this disease. In addition, cultivation nets are washed in acid to prevent carry over of disease-causing agents. As with any marine farming activity, epiphytes and grazers can also be issues faced by the farmers, but nothing as serious as the various rotting diseases. A summary of these studies is presented as a guide for rapid responses and applied management techniques for the amelioration of cultivation diseases, grazers, and harmful epiphytes affecting the two distinct phases of commercial Porphyra cultivation.