Leaves from gold kiwifruit plants, Actinidia chinensis, with dark brown angular spots and flowers that were brown and wilted, first yielded non-fluorescent bacterial colonies following isolation. These bacterial colonies were identified by diagnostic polymerase chain reaction (PCR) as Pseudomonas syringae pv. actinidiae. These samples were obtained from the Te Puke region of New Zealand. All isolates were Gram negative and were levan positive, oxidase negative, potato soft rot negative, arginine dehydrolase negative and tobacco hypersensitivity positive (LOPAT 1a). Sequences of the gyrB and the rpoD genes of these isolates were 100% homologous to sequences of P.s. pv. actinidiae deposited in GenBank including the type strain. Koch's postulates were proven by pathogenicity tests on kiwifruit seedlings.

Three species of Mycosphaerella, namely M. eumusae, M. fijiensis, and M. musicola are involved in the Sigatoka disease complex of bananas. Besides these three primary pathogens, several additional species of Mycosphaerella or their anamorphs have been described from Musa. However, very little is known about these taxa, and for the majority of these species no culture or DNA is available for study. In the present study, we collected a global set of Mycosphaerella strains from banana, and compared them by means of morphology and a multi-gene nucleotide sequence data set. The phylogeny inferred from the ITS region and the combined data set containing partial gene sequences of the actin gene, the small subunit mitochondrial ribosomal DNA and the histone H3 gene revealed a rich diversity of Mycosphaerella species on Musa. Integration of morphological and molecular data sets confirmed more than 20 species of Mycosphaerella (incl. anamorphs) to occur on banana. This study reconfirmed the previously described presence of Cercospora apii, M. citri and M. thailandica, and also identified Mycosphaerella communis, M. lateralis and Passalora loranthi on this host. Moreover, eight new species identified from Musa are described, namely Dissoconium musae, Mycosphaerella mozambica, Pseudocercospora assamensis, P. indonesiana, P. longispora, Stenella musae, S. musicola, and S. queenslandica.

Taro leaf blight (caused by the Oomycete

No abstract

Investigations of sorus ontogeny and sporogenesis in the type species of Ustilago and Sorosporium and in other species usually included in those genera have established criteria far defining Ustilago and Sorosporium. Ustilago is a genus to accommodate smuts that destroy host tissues and whose mycelium is converted entirely to spores after necrosis of host tissues. No columellae or peridia of fungal origin are formed. In Sorosporium species on Saponaria and several grasses, sporogenous hyphal coils are the progenitors of spore balls, this characteristic contrasting with the lack of such organization in Ustilago. Sorosporium saponariae has no well-defined sorus, the spore balls developing from hyphae that grow out of the plant tissues into the spaces between floral organs in buds. The graminicolous species of Sorosporium have sori with well-defined columellae and peridia of fungal origin developed from a soral meristem. It is suggested that smuts with sori developing in this way and having sporogenesis of the Sorosporium type should be grouped in a separate genus. The ontogeny of spore walls of several species of Ustilago and Sorosporium has been elucidated by electron micro- cope studies.