Isoenzyme polymorphism and segregation in isolates of Phytophthora infestans from Japan

Isoenzyme variation of 198 isolates of Phytophthora infestans collected from many locations in Japan during 1987–90, and of four pre-1987 isolates, was examined using starch gel electrophoresis. A previously unreported allele at malic isoenzyme locus/ME (90) was observed. An association between mating types and isoenzyme genotypes at three isoenzyme loci, glucosephosphate isomerase (GPI-1), peptidase (PEP-1) and ME, was found. At PEP-1, the A2 isolates from Japan had a previously unreported genotype (96/96). Normal segregation at the malic isoenzyme locus occurred in a cross of Japanese and Mexican parents. The results provide evidence of a change in the population genetic structure of P. infestans in Japan.     

Factors affecting phytotoxic activity of allelochemicals in soil

Allelopathy is the inhibitory or stimulatory effect of a plant (donor) on other plants (receivers) through the chemicals released from the donor plant to the environment, mostly into the soil. These chemicals may reach the receiver plants in various ways, including leaching from plant foliage, exudation from the roots, and decomposition of dead residue of the donor plants. However, allelopathy in soil is a complicated phenomenon that is affected by soil condition, growth condition of the donor and receiver plants and climatic condition. Allelochemicals in soil are adsorbed on soil solids, and metabolized by chemical and biological reactions during the movement in soil. This behavior is affected by various soil factors, such as soil texture, organic and inorganic matter, moisture and organisms, which affect the phytotoxic activity in soil. If an allelochemical can directly affect the growth of receiver plants in soil, then the allelochemical might be present in the soil water so that it is directly available for absorption by the plant. Thus, it is suggested the concentration of an allelochemical in soil water is a dominant factor directly determining the phytotoxic activity in soil, and the concentration is controlled by soil factors that affect the behavior of adsorption, desorption and degradation in soil.     

Role of underground parts of barnyardgrass (Echinochloa crus-galli (L.) Beauv. var. formosensis Ohwi) in its sensitivity to thenylchlor in soil

In the present study, the phytotoxic activity of top-soil applied with thenylchlor [2-chloro- N -(3-methoxy-2-thieny)-2',6'-dimethylacetanilide] on the growth of rice ( Oryza sativa L.) was dependent on the emergence depth in soil but its activity on barnyardgrass ( Echinochloa crus-galli (L.) Beauv. var. formosensis Ohwi) was only slightly affected by the emergence depth. However, the phytotoxic activity on barnyardgrass and rice was similar irrespective of the different emergence depths in its treatment to all soil layers. Thenylchlor treatment to the mesocotyl of barnyardgrass induced significant inhibition of shoot elongation, whereas the treatment to the coronal root only inhibited the coronal elongation without inhibiting shoot elongation. Absorption and translocation of ¹⁴C-thenylchlor in barnyardgrass were determined in water culture. The different amounts of radioactivity per plant among the treatments to the underground parts were due to the plant part that came in contact with ¹⁴C-thenylchlor. The radioactivity per dry weight was found to be higher in the basal part of the shoot than in its upper part in all treatments to the underground parts. It was suggested that the phytotoxic activity of thenylchlor on the growth of barnyardgrass in soil is induced by its accumulation in the basal part of the shoot through translocation. This primarily occurs after the absorption substantially by the mesocotyl from the herbicide-treated layer and additionally by other underground parts.     

Fetal heart rate monitoring from maternal body surface potentials using independent component analysis

The fetal heart rate is indispensable for monitoring the health of unborn cattle fetuses. To monitor the fetal heart rate, a method employing independent component analysis (ICA) to extract the fetal electrocardiogram (fECG) from potentials measured on the maternal body surface and composed of a mixture of the maternal ECG (mECG), fECG, baseline drift and noise is described. A mixing of the raw data was simplified using a linear time‐invariant model. To separate the fECG from the mECG, baseline drift, and noise, an ICA strategy was applied, using a hyperbolic tangent as the contrast function and treating mutual information with the minimization principle to find the optimum demixing matrix to derive the fECG from the measured signals. After the feasibility of this method was shown on simulated signals obtained by randomly mixing pure fECG, pure mECG, low frequency sinusoidal drift and noise, real signals from three cloned pregnant Holstein cows with 157, 177 and 224‐day gestation periods were used to verify the separation method. The results show that the fECG, mECG, low‐frequency sinusoidal drift and noise can be clearly segregated in simulations, and that the fECG, mECG, baseline drift and noise can be successfully derived from real signals. The ICA approach has great potential in effectively detecting the fECG from maternal body surface potentials.     

Verbena as a trap crop to suppress thrips-transmitted Tomato spotted wilt virus in chrysanthemums

The effect of verbena as a trap crop on the occurrence of western flower thrips, Frankliniella occidentalis, and the incidence of Tomato spotted wilt virus (TSWV) in chrysanthemums were investigated. Verbena cvs. Pink Parfait and/or Fancy Parfait were cultivated alongside chrysanthemum cv. Jimba in a greenhouse in the proportion of 17%–25% of the chrysanthemum plants. Verbena plants attracted vector thrips, reducing western flower thrips colonization of chrysanthemum until flower bud initiation, and markedly suppressing TSWV incidence on chrysanthemums until flowering. Significant quantities of linalool oxide pyran were produced by the flower of cv. Fancy Parfait; and the ratio of cis-linalool oxide pyran, an attractant for vector thrips, to the trans-type was approximately 1 : 5. Our results suggest that cultivation of verbena as a trap crop may be useful in integrated pest management programs as a control for thrips-transmitted TSWV in chrysanthemums.     

Effects of salt stress on ion accumulation and antioxidative enzyme activities of Oryza sativa L. and Echinochloa oryzicola Vasing

The effects of salt stress on physiological factors, such as inorganic ion absorption and antioxidative enzyme activities, of rice ( Oryza sativa L. cv. Anapurna) and Echinochloa oryzicola Vasing were investigated. Although having similar morphology, rice and E. oryzicola possessed considerably different salt-tolerance mechanisms. Echinochloa oryzicola was more salt-tolerant than rice. When exposed to salt stress (100 mmol L⁻¹ sodium chloride, NaCl; six days), E. oryzicola had the ability to limit the accumulation of sodium ions (Na⁺), maintained high potassium ion (K⁺) content and had a constantly higher K⁺/Na⁺ ratio than rice. Rice was not effective in limiting Na⁺ absorption but had a higher antioxidative capacity than E. oryzicola . The constitutive activities of superoxide dismutase (SOD) and catalase of rice were three and five times higher than that of E. oryzicola, respectively. Induced activities of SOD, ascorbate peroxidase and glutathione reductase were also higher in rice than in E. oryzicola . The high antioxidative capacity was one of the tolerance mechanisms used by rice to cope with salt stress. Therefore, the salt tolerant-mechanisms are different between the two plants.     

DNA sequence analysis of ribosomal ITS region 1 of Phytophthora vignae f. sp. adzukicola, the pathogen that causes stem rot of adzuki bean

Sequences of the internal transcribed spacer (ITS) region 1 were used to examine the phylogenetic relationships among races of 19 isolates of Phytophthora vignae f. sp. adzukicola and between this forma specialis and three isolates of the closely related P. vignae f. sp. vignae. The ITS 1 sequences were highly conserved (> 98.7% similarity) among representatives of both formae speciales groups. The results of this study indicate that P. vignae is a monophyletic group. The nucleotide sequence data reported are available in the DDBJ/EMBL/GenBank databases under the accession nos. AB120062–AB120080 and AB120122     

New race of <Emphasis Type="Italic">Phytophthora vignae</Emphasis> f. sp. <Emphasis Type="Italic">adzukicola</Emphasis>, the causal agent of Phytophthora stem rot of the adzuki bean

 A new race of Phytophthora vignae f. sp. adzukicola, designated race 4, is reported from central and western Hokkaido, Japan. The isolates obtained from diseased plants of a new cultivar, cv. Syumari, which is resistant to races 1, 2, and 3, were determined to be a new race by the pathogenic reaction on a set of differential adzuki bean cultivars (cv. Erimo-shozu, cv. Kotobuki-shozu, cv. Noto-shozu, cv. Urasa-shimane, and cv. Syumari). Received: March 7, 2002 / Accepted: August 13, 2002