Fungal pathogens of the winter-planted potatoes in Malta : a review and field survey

Abstract

This work is aimed to give an account about the fungal pathogens that are found in the winter-planted potato crop in Malta and their occurrence in different growing sites. The last report about fungal pathogens in Malta was published in 1998 and hence this work also serves as an update with specific reference to the early-potato crop which is cultivated and harvested between December and April. The dissertation gives an introductory account about the importance of potato crop both locally and, to a greater extent, its historical importance with special reference to the potato blight in Europe with its high economic and social impact. The second part gives an outline about the fungal pathogens previously reported in Malta of which some have been re-confirmed, and also on new pathogens discovered during this survey. Such literature includes nomenclature, morphology, disease cycle and symptoms with regards to the potato plant. The third part explains which potato-cultivated sites that have been randomly selected around Malta, have been surveyed in order to isolate fungal pathogens. Results in which of these sites, fungal pathogens have been isolated are given, which clearly show a prevalence of Phytophthora infestans, with no particular distribution trend but which outcome was dependent on the climatic conditions. Results also reveal two fungal species of less economical impact which have not been reported in Malta before. These are Helminthosporium solani and Pleospora herbarum. The review is concluded by outlining factors which could have contributed to the obtained results, namely climatic conditions and fungicide application, and gives a suggestion of how fungal potato diseases can be controlled in order to reduce losses with minimum impact on the environment with special reference to P. infestans, that is by applying the disease forecast method.