Suppressive effect of acetylated glyceride (Bemidetach™EC) on <Emphasis Type="Italic">Tomato yellow leaf curl virus</Emphasis> transmitted by the whitefly <Emphasis Type="Italic">Bemisia tabaci</Emphasis> on greenhouse tomato plants

Acetylated glyceride (Bemidetach?EC)—a food additive—repels adult sweet potato whiteflies (Bemisia tabaci) and inhibits their mating behavior. We evaluated the effects of acetylated glyceride spraying of greenhouse-grown tomato plants on infestation with B. tabaci and the occurrence of Tomato yellow leaf curl virus (TYLCV) disease under commercial-like conditions. The abundance of adult B. tabaci was significantly reduced by three sprayings of acetylated glyceride, and the TYLCV incidence was significantly suppressed to less than 30% of that in the untreated control. These results suggest that acetylated glyceride sprays suppress the secondary spread of TYLCV in greenhouse-grown tomatoes by lessening B. tabaci adult density.     

Bioassay-guided isolation of a novel chemoattractant for <Emphasis Type="Italic">Ralstonia solanacearum</Emphasis> in tomato root exudates

Tomato root exudates were analyzed using a bioassay to detect the chemoattractant for Ralstonia solanacearum. An activated charcoal-adsorbed fraction of root exudates from tomato cultivar Oogata-fukuju had chemoattractant activity for R. solanacearum strain MAFF 730138. The active component, purified using a Sep-Pak C18 cartridge, an activated charcoal column, diol-modified silica gel, and NH₂-modified silica gel, is a new hydrophobic attractant. The final purified fraction produced a single peak in a diol-modified silica gel HPLC analysis.     

Effects of temperature,zoospore concentration,infection period,and fruit maturity on <Emphasis Type="Italic">Phytophthora palmivora</Emphasis> infection of figs

White powdery rot in figs caused by Phytophthora palmivora is an important disease resulting in severe fruit rot, but is not currently effectively controlled in Japan due to a lack of understanding of its epidemiology. Therefore, the effects of temperature, zoospore concentration, infection period, and fruit maturity on infection of figs were examined by inoculating the fruit with a suspension of P. palmivora zoospores. The zoospores germinated at temperatures from 5 to 35 °C, with the optimum temperature range being 20–35 °C. Germ tube length in zoospore cysts was greatest at 20–30 °C. The disease developed in green figs at temperatures from 20 to 30 °C. Figs inoculated with as few as 10 zoospores per fruit developed severe symptoms at the optimum temperature (25 °C). The minimum infection period required for infection was 2 h at 20–28 °C. All of the figs developed symptoms within an 8 h infection period at 25 or 28 °C, and with a 6 h infection period at 25 °C. All fruit at different stages of development (immature fruit, yellow fruit, and mature fruit) developed symptoms. These results indicate that P. palmivora is capable of infecting figs over a wide range of temperatures, within a short infection period, at a low concentration of zoospores, and at any stage of development. These data could be used to construct forecasting models and develop effective control systems for white powdery rot.     

Estimation of potential area of preparatory irrigation for rainy season lowland rice and supplemental irrigation for dry season cropping using existing reservoirs constructed for aquaculture: a case study in semi-mountainous village,Lao PDR

Paddy and Water Environment - The rural area in Lao PDR has a low yield of rainy season lowland rice, and most rice fields are not utilized for crop cultivation during the dry season. Delay in...     

日本高灌蓝莓采收最适线锯振动速度（摘选）

高灌蓝莓的成熟期不一致,在3～4周时间内需要有选择地采收3～5次。现在日本的蓝莓收获方式是采用一种具有5个速度调节挡的18mm线锯对树枝进行变速振动。为了能够找到采收效率最高且采收效果最好的振动速度,利用高速摄像机对蓝莓采收过程进行记录。之后利用数据统计,回放分析采收过程中的细节,以确定最佳振动速度和振动时间。通过对5种速度的分析,发现Ⅱ挡即频率为1670次min,在果枝周围振动2s是采收的最佳方式。在这种条件下,与3个高速挡同样可以分离87%成熟的蓝莓。同时仅分离了24%未成熟的蓝莓,该结果与Ⅰ挡无显著差异。     

Interspecific hybrids of Cyclamen persicum Mill. and C. purpurascens Mill. produced by ovule culture

Summary Interspecific crosses were made to introduce the scent of flowers of C. purpurascens into C. persicum cultivars and ovule culture was used to rescue the abortive hybrid embryos. Cultivars of C. persicum diploid (CPD, 2n=2×=48) and C. persicum tetraploid (CPT, 2n=4×=96) were the pistillate parents and wild species of C. purpurascens (CP, 2n=34) were staminate parents. After pollination, crossed ovaries were collected periodically and examined using paraffin sections. Histological observations suggested that both hybrid ovules of CPD x CP and CPT x CP should be transferred to culture medium 35 days after pollination. Based up on this observation, crossed ovaries were collected 28 days after pollination and ovules with placenta were transferred to MS (1962) medium containing 3% sucrose. These ovules were cultured in the dark at 25° C. The hybrids (2n=41) derived from CPD x CP had the scent of C. purpurascens, whereas the hybrids (2n=65) derived from CPT x CP had the scent of C. persicum. Although both hybrids had complete genomes from the parents and produced a few viable pollen grains, they failed to yield viable seeds by self- and cross-pollination with fertile pollen grains of C. persicum cultivars.Abbreviations CPD C. persicum diploid - CPT C. persicum tetraploid - CP C. purpurascens     

Carbamate-induced flowering in asparagus (Asparagus officinalis L.) seedlings: optimization of treatment and cultivar variation in flowering response and pollen germination

Optimal carbamate treatment conditions were studied for flower induction in seedlings of an asparagus cultivar ‘Mary Washington 500 W’. Flower induction was most accelerated by soaking seeds in 50 mg l⁻¹ carbamate solution for 12 days at 25 ^°C under the fluorescent light. Longer exposure to carbamate over a 12 day period induced a higher percentage of seedlings to flower. A higher percentage of flowering seedlings were male. Flower induction frequency among seven cultivars through carbamate treatment widely ranged from 13 to 67%. ‘Geynlim’, ‘Mary Washington 500 W’ and ‘Welcome’ exhibited a high percentage of flowering seedlings, while ‘Larac’ and ‘Vulkan’ showed low values. Only male flowers were induced in all-male cultivars. Variation in pollen germination was found within all cultivars. ‘Geynlim’, ‘Cito’ and ‘Mary Washington 500 W’ showed high values of average pollen germination. Application of carbamate compound to induce flower production can rapidly produce homogenic cultivars which include both sexes. This is necessary for genetic studies and breeding purposes. This revised version was published online in August 2006 with corrections to the Cover Date.     

Process to extinction and genetic structure of a threatened Japanese conifer species, <Emphasis Type="Italic">Picea koyamae</Emphasis>

Since the end of the glacial age, Picea koyamae has been sparsely distributed in Japan as a relict species and is presently threatened with extinction. We investigated the population structure and genetic structure of nine populations of P. koyamae. Population size was assessed at 9–135 individuals in habitats ranging from 0.5 to 11.5 ha, and seedlings and saplings were observed in all but one particular population, which had a Sasa-type (bamboo grass) forest floor. The effective number of alleles per locus (N _e) within peripheral populations in the Yatsugatake Mountains was 1.8–2.7, much lower than that of core populations in the Akaishi Mountains (2.8–4.3) using five nuclear simple sequence repeat loci. This finding suggests that genetic variation in these populations has been reduced by isolation from other populations. The standardized genetic differentiation among populations (G′ _st ) was 0.410 and higher than that found in other Japanese conifers, suggesting that isolation and inbreeding have progressed in this species. In two isolated populations at the Yatsugatake Mountains, the fixation index (F _is ) was 0.315–0.354, much higher than the values determined for the other populations (−0.188 to 0.263). This suggests that these two populations have survived several generations while increasing the degree of inbreeding. However, the highest seedling density was in a population with low genetic variation and high F _is . The most serious problems at present appear to be the declining number of mature trees and the deterioration of suitable environments for seedling establishment.     

Strain analysis of lumber containing a knot during tensile failure

We analyzed the strain distribution of lumber containing a knot under a tensile load. The local tensile strain near the knot was measured using the digital image correlation method. Fracture often initiated near the knot where the fiber orientation changed in a three-dimensional manner. The fiber direction in this zone was different from that in the clear part, coinciding with the thickness direction and not with the longitudinal direction of the specimen. Our results disagree with those of previous models that assumed the longitudinal direction of lumber as the direction of crack propagation. Strain analysis showed that a nonlinear region existed around the knot just before ultimate fracture occurred. The results indicated that nonlinear characterization is necessary to determine the failure mechanism of lumber containing a knot, despite the brittleness fracture at the macroscopic scale.