PHYTOPHTHORA-IRANICA, A NEW ROOT PATHOGEN OF MYRTLE FROM ITALY

A homothallic Phytophthora sp. producing persistent and markedly papil late sporangia was isolated, together with P. nicotianae, from the rot ted roots of seedlings of myrtle (Myrtus communis), grown in pots in a commercial nursery in Sardinia, Italy. The homothallic species isolat ed from myrtle was identified as P. iranica on the basis of morphologi cal and cultural characteristics; it differed from other known Phytoph thora spp. belonging to Waterhouse's group I in its higher cardinal gr owth temperatures. In addition, the isolate of P. iranica from myrtle was distinguished from P. cactorum by the electrophoretic protein patt ern and the serological reaction of mycelial extracts, from P. clandes tina by its simple antheridia and the absence of a prominent basal plu g in the sporangia, and from both P. cactorum and P. clandestina by it s persistent sporangia. In pathogenicity tests, P. iranica proved to b e nonpathogenic to wound-inoculated potato tubers, less pathogenic tha n P. nicotianae to apple fruit, and only weakly pathogenic on tomato s eedlings or the stem and roots of myrtle seedlings. This is the only r ecord of P. iranica outside Iran.