Fruit rot of sweet pepper caused by Stemphylium lycopersici in Japan
A severe rot of postharvest fruits of sweet pepper, a variety of Capsicum annuum, was found in Kagawa Prefecture in southwestern Japan in August 1999. A fungus, isolated repeatedly from the diseased fruits and identified as Stemphylium lycopersici, was demonstrated to be pathogenic to fruits of sweet pepper. The disease was new to Japan, and the fungus was added to the pathogens causing fruit rot of C. annuum.
Taxonomic re-examination of several Japanese Stemphylium strains based on morphological and molecular phylogenetic analyses
Most of the many Stemphylium species on record as plant pathogens in Japan have been identified by morphology. Using molecular phylogenetic analysis of four loci (rDNA-ITS, EF-1α, GPD, and vmaA-vpsA) combined, we re-examined the taxonomy of 31 Stemphylium strains that had been identified morphologically before or after their deposit in the NIAS Genebank, Japan. In the present study, these Japanese strains were separated into three groups (Groups A, C, and E). Sixteen Japanese strains formed a new subgroup (designated Subgroup C2) that contained no type or ex-type strains of existing species. Four of the strains had been identified correctly, whereas the other 27 strains appear to have been misidentified based on our phylogenetic analysis. We examined the conidial morphology of four representative misidentified strains selected from each clade. While the morphological characteristics of a strain isolated from Welsh onion resembles those of the S. vesicarium type, this strain belongs to Subgroup C2 rather than Subgroup C1 and, therefore, could not be identified at the species level. Conversely, three pathogenic strains isolated from aster, asparagus, and Chinese chive were re-identified based on our combined morphological and phylogenetic data. We propose the scientific names of the aster leaf spot pathogen as S. lycopersici, and the asparagus Stemphylium leaf spot and Chinese chive brown leaf blight pathogens as S. herbarum.
THE SPORULATION OF HELMINTHOSPORIUM ORYZAE AS AFFECTED BY EXPOSURE TO NEAR ULTRAVIOLET RADIATION AND DARK PERIODS
Investigated was the interrelation of near ultraviolet radiation (3100–4000 A) and darkness to the sporulation of Helminthosporium oryzae. When H. oryzae was grown on potato dextrose agar at 70–75° F and irradiated at intensities of 76–470 μw per cm2: (1) Near ultraviolet stimulated sporulation while visible light did not. (2) Conidiophore development was initiated under irradiation but not in darkness. Both continuous irradiation and intermittent irradiation (2-hour ultraviolet, 2-hour dark cycle) caused formation of conidiophores. (3) Conidia developed only when a period of irradiation was followed by a period of darkness. No conidia developed under continuous irradiation or in continuous darkness. (4) Under a single cycle treatment, the minimum dark period necessary for conidial development following an extended period of continuous irradiation was hours. (5) Under a single cycle treatment, the minimum exposure to ultraviolet followed by an extended dark period necessary to cause moderate to profuse co...