Phycomyces is a unicellular fungus with numerous responses to blue light, including phototropism by the giant sporangiophores. The sporangiophores show a pronounced positive phototropism when illuminated with unilateral blue light. The orientation of the phototropism, positive or negative, is determined by the ratio of the maximal light fluence rate on the proximal side to that on the distal side of the sporangiophore cell. Based on this hypothesis we found that the maximal bending angle was larger in thin sporangiophores than in thick ones, and larger in the sporangiophores with lower contents of cell components such as β-carotene than in those with higher contents. Several parameters influence the determination of the phototropic orientation and the maximal bending angles. To elucidate the photoreceptor and signal transduction systems, genetic and physiological analyses have been carried out using many mutants with abnormal phototropism. Possible photoperception and transduction systems of light signals were discussed.

　Based on joint studies with the BBA, Germany and the NRRL, U.S.A., species of Fusarium were investigated taxonomically and ecologically based mainly on Japanese isolates from gramineaceous substrata (hosts) such as rice and wheat. Among ca. 500 strains, 36 species and six varieties of Fusarium, including 2 species and a variety transferred recently to other genera, were classified from Japan. Four new species and seven new records of species from Japan were also found. During the study, 2 new species, F. nisikadoi and F. kyushuense, were formally described, and F. globosum was reported as a new record from Japan. Macro- and microconidia have been traditionally recognized as important taxonomic characters of Fusarium. Fusarium nisikadoi formed long chains of conidia, which were variable in shape, and their clavate conidia were up to 7-septate. A conidial chain consisting of septate conidia was described as a new morphological character of the genus, and the conidia were not categorized well as either macro-, micro- or mesoconidia as defined previously. Four trichothecene-producing strains originally isolated from diseased wheat and a vinyl plate in Japan were described as F. kyushuense, which produced aerial conidia mostly holoblastically. Japanese strains of F. globosum show different reactions in conidiogenesis to light conditions. Under BLB light, falcate sporodochial conidia were typically induced, but aerial globose conidia were suppressed. Their clavate conidia were longer under BLB. Application of both complete darkness and continuous BLB light is recommended as standard light conditions to identify Fusarium species. Environments surrounding the cultivated host plants may affect distribution of Fusarium species. Occurrence of Fusarium species on wheat spikelets and similar structures was studied. With the geographic shift from northern to southern Japan, the species of Fusarium frequently found on the wheat spikelets gradually shifted from F. avenaceum, to F. sporotrichioides, F. graminearum, and F. incarnatum. Each species of Fusarium may be adapted to a specific environmental condition, even on the same plant host.

　東京都港区の迎賓館庭園に植栽された2種の記念樹，フユボダイジュ（シナノキ科）とヨーロッパナラ（ブナ科）でうどんこ病の発生がみられた．両病原菌のテレオモルフの特徴より前者はわが国のシナノキ類に発生するUncinula oleosa var. zhengiiと同定され，後者は同庭園内のコナラに発生したMicrosphaera alphitoides var. alphitoidesと同一種と考えられた．