Find in Library

Field surveys conducted on nine farms over a 2-year period showed the widespread presence of <i>Phytophthora</i>-related diseases on globe artichoke plants in the main growing area in Sardinia (Italy). Characteristic symptoms included wilting and necrosis of the outermost leaves and dark brown discoloration of stem tissues, as well as root rot. A total of 18 <i>Phytophthora</i> colonies belonging to three species were isolated and characterized. Based on morphological features and ITS sequence data, <i>Phytophthora</i> isolates were identified as <i>P. crassamura</i> (eight isolates) and <i>P. cactorum</i> (four isolates). Six isolates could not be assigned to any formally described species of <i>Phytophthora</i> and are therefore described here as <i>Phytophthora marrasii</i> sp. nov. The ITS phylogeny places <i>P. marrasii</i> in a terminal clade basal to the sister <i>taxa</i> (<i>P. foliorum</i>, <i>P. hibernalis</i>, <i>P. lateralis</i>, and <i>P. ramorum</i>) of the clade 8c. In particular, <i>P. marrasii</i> is phylogenetically related to <i>P. foliorum</i>, a species from which it differs in 62 nucleotides in the ITS region. At the same time, it can easily be distinguished morphologically from <i>P. foliorum</i> mainly because of the low minimum temperature for growth, the bigger and persistent non-papillate sporangia, and smaller oogonia. Pathogenicity tests confirmed that all three <i>Phytophthora</i> species are pathogenic on globe artichokes, which represent a new host for these pathogens.