Occurrence of chrysanthemum virescence caused by “<Emphasis Type="Italic">Candidatus</Emphasis> Phytoplasma aurantifolia” in Okinawa

In 1999, a disease of chrysanthemum [Dendranthema grandiflorum (Ramat.) Kitamura], characterized by virescence of flowers, occurred in Okinawa Prefecture. The causal agent was identified as “Candidatus Phytoplasma aurantifolia” based on 16S rDNA sequencing. The nucleotide sequence data reported are available in the DDBJ/EMBL/GenBank databases under accession number AB247462.     

Mitigation of pyrexia by a Th-1-biased IgG subclass response after infection with equine herpesvirus type 1 in horses pre-immunized with inactivated vaccine

The immunoglobulin G (IgG) subclass response was investigated in horses with or without pyrexia after natural infection with equine herpesvirus type 1 (EHV-1) in the field. All horses were kept at the training centers of the Japan Racing Association and were immunized with an inactivated EHV-1 vaccine before EHV-1 infection. An IgG subclass response dominated by IgGa and IgGb was induced in horses without pyrexia after EHV-1 infection. In contrast, horses that developed pyrexia showed increased IgGc and IgG (T) subclass production in addition to IgGa and IgGb. Although inactivated EHV-1 vaccines are considered to induce a mainly Th-2-biased response, these results indicated that the responses in horses inoculated with inactivated EHV-1 vaccine were not uniform, and that horses with a Th-1-biased response were likely to be protected from pyrexia.     

Host range and properties of <Emphasis Type="Italic">Tomato chlorotic dwarf viroid</Emphasis>

We characterised the host range and physical properties of Tomato chlorotic dwarf viroid. Among the 46 plant species inoculated with the viroid, two in the family Compositae and 23 in the family Solanaceae were found to be systemic hosts. The viroids in the crude sap from diseased tomato plants were thermally inactivated by heating to 100°C for at least 40 min. These viroids also lost their infectivity when diluted in phosphate buffer to at least 10⁻⁶, or after 3 days of incubation at room temperature. However, the infectivity of the viroids in dried crude sap from the plants persisted throughout the 50-day test period.     

Distribution of <Emphasis Type="Italic">tomato chlorotic dwarf viroid</Emphasis> in floral organs of tomato

In situ hybridization was used to analyze the distribution pattern of Tomato chlorotic dwarf viroid (TCDVd) in floral organs of tomato plants. Following TCDVd invasion of floral organs, it became localized only in sepals at an early developmental stage, then reached other floral organs at the flower opening stage, with the exception of part of the placenta and ovules. When distribution of TCDVd was compared with that of Potato spindle tuber viroid (PSTVd), TCDVd was not detected in the outer integument around the embryo sac even though PSTVd was able to invade there, suggesting that such specific distribution might reflect the frequent occurrence of viroid disease on crops caused by PSTVd-seed transmission.     

Disease Resistance of Tissue-cultured Seedlings of Rhododendron after Treatment with Streptomyces sp. R-5

An endophytic actinomycete, Streptomyces sp. R-5, which had been isolated from a field-grown rhododendron plant, was used to protect rhododendron seedlings in tissue culture from Pestalotia disease caused by Pestalotiopsis sydowiana. R-5 had intense antagonistic activity against P. sydowiana without adversely affecting the seedlings in glass flasks. A suspension of R-5 was spread on the surface of the multiplication medium in glass flasks in which seedlings were growing. Ten days later, the 4th upper leaf of seedlings was inoculated with P. sydowiana and incubated for 14 days. In controls untreated with R-5, substrate mycelia of P. sydowiana grew on all leaves and stems above and below the 4th leaf within 2–3 days of inoculation. Such growth resulted in the wilting death of 54% of seedlings by 14 days. In contrast, only the inoculated leaves turned brown in ca. 90% of seedlings growing on medium treated with R-5. None of these seedlings died. Thus, treatment of the medium surface with R-5 efficiently protects the seedlings from infection by P. sydowiana. Scanning electron microscopy revealed that substrate mycelia of R-5 grew on and beneath the cuticle of leaves of the treated seedlings. Fluorescent microscopy showed that R-5 was also inside the leaves. Received 8 June 2001/ Accepted in revised form 4 July 2001     

Genetic polymorphisms in Japanese fragrant landraces and novel fragrant allele domesticated in northern Japan

Rice fragrance is an important characteristic for Southeast Asian consumers, and fragrant landraces from Japan were first recorded in the 17th century. Principal component analysis clearly showed that Japanese fragrant landraces were genetically different from non-Japanese fragrant landraces. Japanese fragrant landraces were composed of six clades, none of which carried the most common fragrance mutation, an 8-bp deletion in exon 7 of Badh2. Fragrant landraces comprised two major groups carrying different Badh2 mutations. One group carried a known SNP at exon13 and the other a SNP at the exon1-intron1 junction as splicing donor site. The latter was considered to be a potential splicing mutant group as a novel allele at Badh2. Heterozygosity (He) scores in the two fragrant groups were not significantly different from non-fragrant landraces and modern cultivars. However, lower He scores were found around the Badh2 locus in the two groups. The potential splicing mutant group showed a more extended haplotype than the E13 SNP group. A likely causal factor responsible for loss of function is a novel splicing mutation allele that may have been generated quite recently. The fragrance allele has dispersed as a result of out-crossing under local environmental conditions.     

Dual inoculation of peanut with Glomus sp. and Bradyrhizobium sp. enhanced the symbiotic nitrogen fixation as assessed by 15N-Technique

Abstract

The response of peanut (Arachis hypogaea L.) to inoculation with vesicular-arbuscular mycorrhizal (VAM) fungi (Glomus etunicatum) and Bradyrhizobiurn sp. was studied in pots by the acetylene reduction activity (ARA) and ‘A-value’ methods. The soil used was a Light-coloured Andosol and the treatments consisted of the inoculation of VAM fungi only, inoculation of Bradyrhizobium only, dual inoculation of VAM fungi and Bradyrhizobium and control, under non-sterilized and sterilized soil conditions.

In the non-sterilized soil the ARA and nitrogen fixation determined by the ‘A-value’ method increased significantly only by dual inoculation of VAM fungi and Bradyrhizobium at 100 days after planting (DAP), but no significant difference was observed at 70 DAP. In the case of dual inoculation, 75% of the nitrogen of the plant was derived from fixation whereas the plants inoculated only with Bradyrhizobium derived 68% of their nitrogen from fixation and the control plants, 64%. Amount of P in plant increased significantly only by dual inoculation with VAM fungi and Bradyrhizobium.

In the sterilized soil a highly significant increase in the ARA was observed of the dual inoculation at all the sampling times. Nitrogen fixation determined by the A-value technique and N and P contents in plant also increased significantly by dual inoculation. Results obtained by the A-value method showed that plants with dual inoculation derived 68% of their nitrogen from fixation while the plants inoculated only with Bradyrhizobium, 38%.

From our this study we conclude that nitrogen fixation as well as N and P contents in peanut increased significantly only by dual inoculation with VAM fungi and Bradyrhizobium.     

The role of arbuscular mycorrhizal fungi and cattle manure in the establishment of Tocoyena selloana Schum. in mined dune areas

In mined dune areas, revegetation with manured seedlings of native species is a common practice. Establishment of mycorrhized Tocoyena selloana seedlings in the mined coastal sand dunes of Northeast Brazil was tested. In greenhouse, seedlings were grown in substrates with 0, 5, 10, 15 or 20% cattle manure proportions and inoculated with Acaulospora longula, a mixture of native arbuscular mycorrhizal fungi (AMF) or uninoculated. The seedlings responded positively to the inoculation, but growth was limited in the absence of manure, independently of inoculation, and was higher with fertilizing doses ≥10%. The seedlings transplanted to the field were grown in a substrate with 16.5% manure and inoculated with A. longula or Gigaspora albida. After 13 months, 19 AMF species were identified in the rhizosphere and the inoculated plants were more colonized than those uninoculated. Plants associated to G. albida were taller and those associated to A. longula had a tendency of higher biomass than the uninoculated ones. Even though this tendency was not statistically significant, considering the effect on height and the low cost of inoculation it may be a feasible practice to maximize environment restoration.     

Toward sustainable management of small cetacean fisheries around Japan

Abstract:   The management of Japanese domestic fisheries for small cetaceans has been based on a traditional approach that involves only the best set of assumptions and data. However, uncertainty, which is pervasive and inevitable for most fisheries resources, often leads the traditional approach to serious failure. Here is presented the basic framework of a simulation-based approach with a simple Bayesian method that is applicable to Japanese fisheries for small cetaceans. For illustration, the simulation model was applied to Dall's porpoise data in order to investigate the robustness of several management procedures against uncertainty. The simulation showed that the current management procedure, based on only the best values, could fail to manage the stocks at a considerably high probability. However, the use of the conservative management procedure, potential biological removal, permits the sustainable harvesting of Dall's porpoise for at least 100 years into the future, even under uncertainty. In conjunction with a firm structure for implementation of management procedures, the spread of simulation-based approaches will quickly enable successful sustainable management of small cetaceans.