New Leaf Spot Disease of Cymbidium Species Caused by Fusarium subglutinans and Fusarium proliferatum

Fusarium species were consistently isolated from yellow, swollen spots with reddishbrown centers and small black spots on leaves of Cymbidium plants in the greenhouse. Fusarium subglutinans caused the yellow spots and Fusarium proliferatum caused either the yellow or the black spots. We propose the name “yellow spot” for the new disease. To denote differences in their pathogenicity to orchid plants, we designate the population causing yellow spot as race Y and that causing black spot as race B of F. proliferatum. Received 29 October 1999/ Accepted in revised form 10 March 2000     

Molecular Monitoring of hrpB-disrupted Mutant of Ralstonia solanacearum in Tomato Plants

A nonpathogenic mutant of Ralstonia solanacearum was produced by the insertion of transposon Tn4431. The mutagenized gene was then cloned from a genomic DNA library by the gene tagging method, using the labeled lux operon located on Tn4431 of pUCD623 as a hybridization probe. From nucleotide sequence analysis of the transposon-inserted genomic clone, the hrpB gene was shown to be disrupted by the inserted transposon. Tomato plants were inoculated with the hrpB-disrupted mutant bacteria, for which multiplication and translocation were then monitored using the colony hybridization method. In addition, the original pathogenic bacteria in which the lux operon had been functionally ligated with the genomic promoter were also used for inoculation and traced by their bioluminescence. Multiplication of the hrpB-disrupted mutant was suppressed initially in the invaded root tissues and then in upper hypocotyl after translocation, suggesting that the pathogenic strain of R. solanacearum overcomes at least two steps of host responses expressed in root and hypocotyl tissues. Thus, our approach for molecular monitoring of the bacteria enabled us to precisely analyze the infection behavior of the pathogenic bacteria in planta. Received 16 April 1999/ Accepted in revised form 10 August 1999     

Histopathological changes in the pancreas due to decreased pancreatic blood flow in a canine tachycardia-induced cardiomyopathy model

In dogs, pancreatic acinar cell injury is thought to be caused by decreased pancreatic blood flow due to heart failure. In previous our report, it demonstrated that decreased heart function causes a significant decrease in pancreatic blood flow in heart failure dog model caused by rapid ventricular pacing (RVP). However, the types of histopathological changes remain unclear. We aimed to verify the types of histopathological changes occurring in the pancreatic tissue due to decreased heart function. After RVP for 4 weeks, atrophy of pancreatic acinar cells, characterized by a decrease in zymogen granules, was observed in all areas of the pancreas. In conclusion, the result of this study suggests that attention should be paid to ischemia/hypoperfusion injury in the pancreas.     

Evaluation of colorimetric pH strips for wild animal meat using image analysis

Colorimetric pH strips (MColorpHast™) are very convenient to use, but the decision of pH is based on an individual's color perception and is, therefore, subjective. We developed a pH calculation program for the image of coloring strips on CIE1976 (L*a*b* color space), which slightly underestimated human judgment as the color of pH darker. This image analysis and three individuals' judgments were used for evaluating the strip's features for various qualities of meat from wild animals, and the results were compared with the assessments based on potentiometric pH. In both methods, dipping the strips in distilled water just before use improved the regression coefficient compared with that mentioned in the manual. The image analysis showed higher correlation than human judgments but slightly underestimate pH by a maximum of 0.13 unit from the regression line of the potentiometric pH. In addition, the image analysis revealed meat pigment changed pH higher on the color scale in the lower meat pH region. The strips must be used according to the manual, but dipping is effective when the meat surface is dry, and keeping the strips from touching the meat drip is important in lower pH region because the pigment affects the color of pH.     

Quercetin-dependent reduction of salivary nitrite to nitric oxide under acidic conditions and interaction between quercetin and ascorbic acid during the reduction

A salivary component, nitrate, is reduced to nitrite in the oral cavity. Polyphenols in foods are mixed with nitrite in the saliva to be swallowed into the stomach. An objective of the present study is to elucidate reactions between a polyphenol quercetin and a nitrite under acidic conditions. Nitric oxide, which is formed by the reactions between nitrous acid and quercetin or ascorbic acid (AA), can be measured using an oxygen electrode in the saliva as well as a buffer solution. The initial oxidation of quercetin was inhibited by AA, and quercetin enhanced the oxidation of AA, suggesting AA-dependent reduction of quercetin radicals, which might be formed during the oxidation of quercetin by nitrous acid. On the basis of the above results, the usefulness of an oxygen electrode for the measurement of nitrite-dependent nitric oxide formation under acidic conditions is proposed and the possible mechanism of reduction of nitrous acid by quercetin and the interaction between quercetin and AA, which is a normal component in the gastric juice, for the reduction of nitrous acid is discussed.     

Effect of spore inoculum and agricultural practices on the vertical distribution of the biocontrol plant-growth-promoting bacterium <Emphasis Type="Italic">Pasteuria penetrans</Emphasis> and growth of <Emphasis Type="Italic">Meloidogyne incognita</Emphasis>-infected tomato

Three concentrations of Pasteuria spores applied to soil and some agricultural practices were evaluated for their effects on spore attachment to nematodes and biocontrol of Meloidogyne incognita on tomato in a microplot experiment. Applications of Pasteuria at concentrations of 5᎒¹⁰ spores/m² increased tomato fruit yield per plant by 46% compared to non-Pasteuria treatments but also increased nematode densities in soil at harvest time. M. incognita juveniles recovered from plots where Pasteuria was applied at 5᎒¹⁰ spores/m² showed greater spore attachment than those with application rates of 2.5᎒⁹ spores/m² or 5᎒⁹ spores/m². Pasteuria spores penetrated to 30-40 cm soil depth in a volcanic ash sandy soil after application of spore suspensions to the soil surface. Densities of over 2.5᎒⁴ spores/g of soil were reached at 0-30 cm soil depth only when the application rate was 5᎒¹⁰ spores/m², but at harvest and after fallow densities of about 2.5᎒⁴ spores/g of soil were also reached in the top 10 cm of soil at 2.5᎒⁹ and 5᎒⁹ spores/m² application rates. Spore densities in soil decreased after 6 months of fallow when densities at harvest time were higher than 10⁵ spores/g of soil. Tillage and additional watering 2 days after spore application increased spore densities in soil at harvest throughout the soil depth (0-40 cm).