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Journal of Nematology (1)
Journal of nematology (1)
Scientific Reports (1)
Takemoto, Shuhei (3)
Futai, Kazuyoshi (1)
Hara, Naoki (1)
Koyama, Kohei (1)
Mota, Manuel M. (1)
Niwa, Shigeru (1)
Okada, Hiroaki (1)
Takeuchi, Yuko (1)
Year of Publication
Morning reduction of photosynthetic capacity before midday depression
Midday depression of photosynthesis has important consequences for ecosystem carbon exchange. Recent studies of forest trees have demonstrated that latent reduction of photosynthetic capacity can begin in the early morning, preceding the midday depression. We investigated whether such early morning reduction also occurs in an herbaceous species, Oenothera biennis. Diurnal changes of the photosynthetic light response curve (measured using a light-emitting diode) and incident sunlight intensity were measured under field conditions. The following results were obtained: (1) the light-saturated photosynthetic rate decreased beginning at sunrise; (2) the incident sunlight intensity on the leaves increased from sunrise; and (3) combining (1) and (2), the net photosynthetic rate under natural sunlight intensity increased from sunrise, reached a maximum at mid-morning, and then showed midday depression. Our results demonstrate that the latent morning reduction of photosynthetic capacity begins at sunrise, preceding the apparent midday depression, in agreement with previous studies of forest trees.
Effect of Storage Temperature on Soil Nematode Community Structures as Revealed by PCR-DGGE
Journal of Nematology
The optimal duration and conditions for storage of soils collected for nematode community analyses are unknown. To study this issue, three types of soils with different geographical origins from the subarctic to cool-temperate Japan were kept at three temperature levels (5, 10, and 20°C) for up to 8 wk following collection. During the storage period, nematode population density was measured, and community structure was assessed by polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE). No significant changes in the population density or diversity of nematodes (Shannon-Wiener Diversity Index) were observed during storage compared to initial states, except that density in an andosol collected from Tsukuba, Central Japan decreased significantly after 28 d of storage at 5°C. However, a regression analysis showed a declining trend in nematode density in the latter half of the storage period when soils were stored at 5 or 20°C, depending on the geographic origin of the soil. These results indicate that soils can be stored for 14 d at 5–20°C, with 10°C as optimal. This is the first study to experimentally determine the optimal preservation conditions for nematode assemblages in soils that are to be analyzed using PCR-DGGE.
biodiversity; ecology; method; soil fauna
Comparative Studies between Portuguese and Japanese Isolates of the Pinewood Nematode, Bursaphelenchus xylophilus
Mota, Manuel M.
Journal of nematology
Comparative studies between Portuguese (T and HF) and Japanese (S10, T4, C14-5 and OKD-1) isolates of the pinewood nematode Bursaphelenchus xylophilus have been made in order to provide information to better understand the possible origin of the Portuguese isolates, recently introduced in the European Union. The main comparative aspects investigated were pathogenicity (seedling mortality ratio), sexual compatibility, and DNA sequences of the rDNA region. Four-year-old Japanese black pine (Pinus thunbergii) seedlings were used as host plants for pathogenicity tests. The Portuguese isolates, and in particular isolate “T,” propagated in higher numbers than the Japanese isolates within pine seedlings. All combinations of crossings produced viable progeny, with higher numbers obtained when crossings were made between Japanese and Portuguese isolates, a possible situation of heterosis and/or inbreeding depression. Reciprocal crossings yielded different values, which may reflect a sex effect (maternal inheritance, mtDNA). Regarding DNA sequencing, both Portuguese isolates displayed nearly identical ITS 1, ITS2, and 5.8S rDNA base sequences as the Japanese isolates. Although biologically very similar, and possibly reflecting a common origin, the Portuguese isolates may present a serious threat to Japanese black pine, due to their higher virulence.
Portugal; Japan; pathogenicity; sexual compatibility; DNA sequence
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