In a survey for effective biocontrol agents of Colletotrichum orbiculare, causal agent of cucumber anthracnose, 43 (MBCu series) and 135 (MBPu series) endophytic actinomycete strains were recovered from surface-sterilized organs of cucumber (Cucumis sativus) and pumpkin (Cucurbita moschata) plants, respectively. The strains were cultured with C. orbiculare on IMA-2 agar medium to determine their in vitro antagonistic ability. Eleven strains that strongly inhibited hyphal growth of the pathogen were selected as potent antagonists. Detached cotyledons of cucumber were soaked in a spore suspension of an antagonistic strain 1 day before challenge-inoculation with the pathogen, and six of these antagonists 36, 42, 45, and 56, significantly reduced the number and size of the lesions on the cotyledons compared to the untreated control. In the same way, these six strains inhibited lesion development on attached leaves of 3-weekold cucumber seedlings. Strain MBCu-56, the most suppressive of the strains, was selected for further tests. Its suppressiveness increased as concentrations increased; pretreatment of leaves with the strain at 10 7 , 10 8 and 10 9 cfu/ml suppressed disease by 72, 79 and 93%, respectively. These results strongly indicated that MBCu-56 has strong potential for controlling cucumber anthracnose. Based on the taxonomic characteristics and 16S rDNA sequence, MBCu-56 was identified as Streptomyces sp. With scanning electron microscopy, the substrate mycelia of the strain were seen to colonize the surface of leaves above the cuticle. Some hyphae also penetrated and grew underneath the cuticle.
In the present study, large-eddy simulations (LESs) were performed to investigate mixed layer depth (MLD) and sea surface warming (SSW) under diurnally cycling surface heat flux in the heating season, in which a mixed layer (ML) is shoaling on intraseasonal time scales. The LES results showed that the diurnal cycle makes the MLD greater (smaller) at lower (higher) latitudes than the MLD without the cycle. Time scales of the wind-induced shear and the surface heat are a key to understand this latitudinal dependence of the diurnal cycle effects. The wind-induced shear-driven turbulence developed from early morning and became strongest at half the inertial period ( T i/2), while nighttime cooling weakened the ML stratification until the end of the nighttime ( T24 = 24 h). At lower latitudes where T i/2 > T24 (lower than 15°), the shear-driven turbulence continued to grow after T24 and determined the time of the greatest MLD. Thus, the shear-driven turbulence shaped the latitudinal dependence of the MLD, though convective turbulence helped further deepening of the ML. At higher latitudes ( T i/2 < T24), on the other hand, the shear-driven turbulence ceased growing before the nighttime cooling ended. However, reduced stratification due to the nighttime cooling supported the shear-driven turbulence to continue deepening the ML. Thus, the nighttime cooling shaped the latitudinal dependence of the MLD at higher latitudes. The MLD change induced by the diurnal cycle altered the SSW rate. At higher latitudes, the diurnal cycle is expected to reduce the MLD and increase the SSW by 10% in the heating season.
The observed sea level (SL) around the Japanese coast shows a peculiar multidecadal variation with the peak in the 1950s followed by the gradual fall until the 1970s and the rebound continuing to the present, making the recent SL rise less remarkable in the historical record. The multidecadal SL variability of an ensemble mean of the Coupled Model Intercomparison Project phase 6 historical simulations using the Meteorological Research Institute Earth System Model version 2.0 (MRI‐ESM2.0) compares well with the observation and is greater than the piControl one, implying the observed variability could be a forced one. The MRI‐ESM2.0 simulations for the Detection and Attribution Model Intercomparison Project suggest the increase in anthropogenic aerosols and greenhouse gases caused the fall and rise of the SL, respectively. Additional sensitivity runs indicate the surface heat loss in the North Pacific due to anthropogenic aerosols plays a dominant role in the SL fall.
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