Induced Resistance in Hypocotyl of Cucumber by Infection with Colletotrichum lagenarium in Leaves

Localized infection of cucumber leaves with Colletotrichum lagenarium induced resistance against infection after challenge inoculation with pathogenic fungi, including C. lagenarium and Pythium ultimum var. ultimum. Systemic acquired resistance in the hypocotyl was observed when challenge inoculation was made 4 to 7 days after the first inoculation of cotyledons. Seven days after the first inoculation of a primary leaf, induced resistance against the challenge inoculation in the hypocotyl was also observed. However, the hypocotyl did not develop induced resistance when plants were challenged by a wound inoculation with P. ultimum. Received 9 June 1999/ Accepted in revised form 13 December 1999     

Black Rot of Artichoke Leaves Caused by Two Phoma Species in Japan

Phoma macrostoma var. incolorata and P. exigua var. exigua were isolated from leaf spots of artichoke in Mie Prefecture, Japan in June 1997. Colonies of P. macrostoma var. incolorata grew fast, pigmented the medium vinous without staining the mycelium, and changed blue with NaOH. Conidial size in culture was 3 to 10 μm × 2 to 4.5 μm. Colonies of P. exigua var. exigua grew fast without pigmentation and changed yellow-green with NaOH. The conidia were sometimes septate, and size of aseptate conidia was 4 to 9.5 μm × 2 to 3.5 μm. These fungi produced gray, round spots on artichoke leaves. This report is the first on the occurrence of artichoke black rot caused by P. macrostoma var. incolorata and P. exigua var. exigua in Japan. Received 5 July 2001/ Accepted in revised form 12 March 2002     

Predicting the population dynamics of three understory broad-leaved evergreen species under the influence of Sika deer in primary and secondary forests of mid-western Japan

We examined the population dynamics of three broad-leaved tree species with different susceptibilities to deer predation. Simulation analysis was conducted using a size-structured matrix model for a primary forest plot (PP) and a secondary forest plot (SP) with 56% and 12% evergreen conifer composition in the canopy, respectively. In both plots, populations of Neolitsea sericea, a species that is susceptible to deer predation, initially declined significantly but eventually leveled off. The number of small stems decreased, while that of larger stems increased, indicating that the population dynamics of N. sericea are strongly affected by browsing pressure and that the number of large trees is important for population maintenance. When we examined two deer-resistant species, Pieris japonica and Illicium anisatum, the population of P. japonica increased in the SP and decreased in the PP, whereas that of I. anisatum increased in both plots, likely because mortality tends to increase in persistently dark environments. No significant difference was observed between the present and predicted size distributions of resistant species in the PP. Competition for resources is expected to intensify in the SP as a result of the predicted increase in large stems of the resistant species I. anisatum. Therefore, a specific conservation and management strategy for tree species should be considered for each forest type under the influence of Sika deer.     

Specific Detection of Tomato Pathotype of Verticillium dahliae by PCR Assays

Verticillium dahliae Klebahn is the causal agent of tomato wilt disease. Isolates of V. dahliae can be classified based on pathogenicity to tomato, but the pathotypes are indistinguishable in morphology. We designed PCR primers for specific detection of isolates pathogenic to tomato (tomato pathotype) from the sequences of a pathotype-specific gene, vdt1. With the primer pair Tg5/Tc3, a PCR product (approximately 3.2 kb) specific to tomato pathotype was amplified from the genomic DNA of isolates. Using the primer pair, a tomato pathotype isolate was specifically detected from hypocotyls of inoculated tomato and eggplant. On the other hand, no amplification was observed from non-tomato pathotype isolates of V. dahliae, some other wilt pathogens of tomato and a healthy host plant. Therefore, the primer pair can be useful for pathotype-specific detection of V. dahliae as well as for diagnosis of wilt disease of tomato plant. Received 7 September 2001/ Accepted in revised form 3 December 2001