We analyzed the quantitative trait loci (QTLs) for cold tolerance at the booting stage of a cold-tolerant rice variety, Norin-PL8, which harbors cold tolerance genes derived from a cold-tolerant variety, Silewah. We found that 5 segments on chromosomes 1 (2 segments), 3, 4 and 8 were incorporated from Silewah into Norin-PL8. The association between the incorporated segments and cold tolerance was examined using BC₁F₅ lines between Norin-PL8 and Kirara397, which is a cold-sensitive commercial variety. The segment on the short arm of chromosome 3 and that on the long arm of chromosome 4 were associated with cold tolerance, indicating the presence of QTLs for cold tolerance on chromosomes 3 and 4. Interval mapping on the long arm of chromosome 4 suggested that 2 QTLs were located in the centromeric half of the incorporated segment. In order to confirm the results of interval mapping, we developed a set of near-isogenic lines (NILs). Comparison of the levels of cold tolerance of the NILs indicated that either the proximal end or the center of the segment is necessary for cold tolerance. Based on these results, it was concluded that there are at least 3 QTLs for cold tolerance on chromosomes 3 and 4.

View full abstract

Using an improved method for evaluating powdery mildew (Sphaerotheca cucurbitae) resistance in cucumber, experiments were conducted for the breeding of varieties resistant to powdery mildew that would be adapted to greenhouse cultivation during the period from winter to spring in Japan. The relationship between the resistance to the pathogen and the ambient temperature was analyzed by spray inoculation of a conidial suspension under controlled conditions. Although the varieties, Asomidori-5-gou and Natsufushinari were resistant at temperatures between 25 to 30ºC, they became susceptible at 15 to 20ºC. The resistance was affected by the duration of the exposure to 30 and 15ºC during the day. To screen resistant varieties and lines independently of the temperature, 295 cucumber accessions were inoculated at 20 and 26ºC. All the accessions tested could be divided into 3 types based on the difference in the resistance response to temperature. Many of the resistant accessions were Chinese varieties and lines. PI197088-5, a progeny of PI197088 which originated in India, displayed the highest level of resistance among all the accessions. Thus PI197088-5, whose resistance is temperature-independent appears to be the most suitable parent for the breeding of powdery mildew-resistant cucumber varieties. The inheritance of powdery mildew resistance in PI197088-5 was analyzed using Natsufushinari (resistant under high temperature conditions) and Sharp 1 (susceptible). As a result it was considered that the powdery mildew resistance in PI197088-5 was due to 2 gene pairs, a recessive gene and an incompletely dominant gene, with the genotype designated as aaBB, while the genotype of Natsufushinari was designated as aabb and that of Sharp 1 as AAbb. The nature of the host-pathogen interaction in PI197088-1 which is the sib-line of PI197088-5 was observed microscopically. The retardation of hyphal growth and development was observed at 2 days after inoculation. Conidia were hardly formed on the epidermis and the number of haustoria in the epidermal cells of PI197088-1 was much lower than that in the susceptible variety Sharp 1. Fluorescence of epidermal cells was observed along the hyphae in PI197088-1 at 6 days after the inoculation, suggesting the existence of a hypersensitive reaction.

View full abstract

In order to easily and inexpensively renovate grasslands whose yield had declined or botanical composition had deteriorated, a new pasture renovator based on the design of a rotary tilling device that performs narrow ditching, over-sowing in the ditch, fertilizer application, covering with soil and compacting in one pass was developed. It makes a T-shaped ditch with a combination of shallow L-shaped working blades and deep-tilling plate-shaped straight blades. It is mounted on a tractor with a power exceeding 44 kW. Test results revealed that this machine enabled to save more labor in partial tilling renovation than in overall renovation and that it effectively improved the vegetation of the land.

View full abstract

To obtain basic information for the production of healthy and vigorous larvae and juveniles, a comparative study on meristic variations and bone abnormalities between wild and laboratory-reared red sea bream, Pagrus major, was undertaken. Although 95% of the specimens of wild juveniles had a definite number of dorsal fin rays, reared juveniles exhibited extensive variations, and the latter had fewer pectoral fin rays than the former. Bone abnormalities included the transformation of spines to soft rays, shrinkage of lower jaw, pug-headness, shrinkage of anterior centra, fusion of vertebrae, abnormal pterygiophores, etc. Detailed observations of cleared and double-stained specimens revealed that wild juveniles had an average of 0.2 abnormal bones per specimen, whereas, the reared ones had an average of 2.04-21.4 abnormal bones per specimen, depending on the groups. Therefore, reared fishes showed many abnormalities, although they appeared to be normal based on external observation. The causes of these abnormalities have not been elucidated, except for the lordosis. Abnormalities of reared fishes seemed to affect bones and cartilage as well as other tissues, such as the deformity of the inter-nostril epidermis in one case. It is likely that various defects associated with rearing conditions induce a variety of abnormalities. Aquaculturists should attempt to produce larvae and juveniles which are similar in morphological, behavioral, physiological and biochemical characteristcs to wild ones.

View full abstract

The phenotypes related to tea gray blight resistance were evaluated by the artificial inoculation method in the accessions of tea germplasm preserved at the National Institute of Vegetable and Tea Science in Makurazaki, Kagoshima Prefecture. The genotypes of 453 plants including 89 main tea cultivars in Japan were also determined by using the parent-offspring genetic analysis of many cross combinations. A wide variation in the resistance of tea plants to tea gray blight was observed both in terms of phenotypes and genotypes. The majority of the Assam plants (Camellia sinensis var. assamica) showed a high level of resistance and very few variations, both in genotypes and phenotypes. The Japanese native plants (C. sinensis var. sinensis) showed a wider genetic diversity than any other groups of plants in the resistance to tea gray blight. Since many of the tea plants derived from other countries were highly resistant to the disease and harbored 2 Pl₁ genes which confer a high level of resistance, they are very important materials for the breeding of cultivars that are resistant to the disease. The phenotype and genotype analysis was found to be very useful to identify doubtful cultivars.

View full abstract

A comprehensive series of technologies was developed for the enhancement of rice production, laborsaving crop management, land improvement and water-saving production of vegetables and fruits for the improvement of cropping systems in rainfed lowland areas of Northeast Thailand as follows: (1) No-tillage dry direct seeding cultivation of rice was developed by the combined use of a no-tillage row seeder of the riding type and appropriate crop management, (2) Productivity of KDML105 was enhanced by the use of slow-release nitrogen fertilizers and soil conditioners, (3) A mechanized crop management system was developed for rice and introduced crops along with the development of rational weed control in rainfed paddy fields, (4) Land improvement technologies such as prevention of water leakage and deep tillage enhanced the water retention capacity and productivity of rice, (5) Effective use of agri-byproducts such as rice straw and husks was developed for soil and crop improvement, (6) Hood tunnel, vinyl-mulching and underground drip irrigation were effective for the cultivation of vegetables and fruits with increased water use efficiency.

View full abstract

Narrowleaf vetch (Vicia angustifolia L.) (NLV) is a legume widely distributed in the Eurasian continent. Although commonly growing as a weed in cultivated areas, NLV could become a suitable species for cultivation as a green manure crop to increase the nitrogen content of soil. We examined NLV and a common green manure crop, Chinese milk vetch (Astragalus sinicus L.) (CMV), both in monocultures and in mixed cropping of the 2 species. The nitrogen-fixing activity and root nodule activity of the species were determined and the effects on the nitrogen (N) supply to soil were evaluated. CMV produced more plant N than NLV, largely as a response to better growth after the over-wintering period. The amount of atmospheric N fixed by NLV (4.3 g m^-2) was only half of that fixed by CMV (8.6 g m^-2). Nevertheless, the amount of N in NLV (up to 14 g m^-2) was sufficient to supply the demand of the following crop. The mixed culture of CMV and NLV performed better than the monoculture. Since developing countries cannot afford to invest money on nitrogenous fertilizers or legume seeds, the use of the widely distributed NLV as a green manure might be effective and contribute to the sustainability of cropping systems.

View full abstract

Lactococcus lactis subsp. lactis biovar. diacetylactis DRC1 carries more than 6 plasmids, including a 7.4 kb cryptic plasmid, which was designated as pDR1-1. The pDR1-1 plasmid was found to significantly affect the maximum specific growth rate (µ_max) of the host cells because of its limiting effect on growth. To investigate the properties of the limiting effect, the entire nucleotide sequence of pDR1-1 was determined. It consisted of 7412 bp, and 6 open reading frames (ORFs) were identified. The first ORF showed a high degree of similarity to a family of replication genes (rep) that are commonly found in lactococcal strains. The rep gene in pDR1-1was followed by a second ORF of unknown function. Directly downstream of the second ORF, a third ORF was found, that showed homology to the S subunit from type I restriction/modification systems. No significant similarity to the contents of the database was found for the other ORFs. PCR analysis was carried out in order to detect pDR1-1 in the other L. lactis strains. The µ_max of the pDR1-1-positive strain was the same as that of DRC1. These results suggest that the load of pDR1-1 (or pDR1-1-like plasmid) is a major factor influencing the µ_max of DRC1 because of its limiting effect on growth, an effect which is much more pronounced than that produced by the overall load of other coexisting plasmids.

View full abstract

To determine the presence of enterotoxigenic Escherichia coli (E. coli) (ETEC), Shiga toxin-producing E. coli (STEC) and attaching and effacing E. coli (AEEC) were collected in swine and in a water system in 17 swine farms in the Can Tho province of the Mekong delta. A total of 258 samples which were collected from swine feces (n=169), from feed (n=39) and from water (n=50) in the irrigation system were examined by PCR to determine whether they harbored the stx, eae, and enterotoxin genes. STEC was detected in 10 of 169 (6%) fecal samples, and AEEC in 5 fecal samples (3%). Both STEC and AEEC were detected in one fecal sample. AEEC was mainly detected in fecal samples from pigs that were less than 4 months old. STEC or AEEC was detected in 18 samples from 5 out of 17 (29%) farms. On the other hand, STEC and AEEC were also detected in the water and feed samples. ETEC was not detected in diarrhea samples.

View full abstract

In this study, a kenaf harvester was developed and the optimum harvesting period and effective field capacity were determined. The kenaf harvester that was a modified sugarcane harvester had a 57 kW engine and ran with a crawler. To cut kenaf stems properly, a cutter equipment specific to kenaf was developed, to control the flow of harvested kenaf stems and prevent the basts of kenaf from winding around the cutter part of the drum. This machine enabled to cut kenaf stems with a length of about 22 cm each, regardless of the traveling speed, and harvest could take place from the period of flowering to the period of killing frost. In this machine, 2 types of carriers were developed for the harvested kenaf stems: a net bag type and a conveyor type. The net bag type consisted of a net bag container with a capacity of about 500 kg located behind the machine. With this type, although the field capacity efficiency was low because much time was spent on unloading the materials, the harvester could be handled with one operator. The effective field capacity was about 6.6 a/h. The conveyor type consisted of a belt conveyor system located behind the machine. Kenaf was conveyed to a wagon tractor by the conveyor system. In the conveyor type, the operations were slower (15%) than in the net bag type, but the effective field capacity was about 13.9 a/h.

View full abstract