寒地水稻生长发育动态研究初探

以黑龙江省主栽的两个水稻品种为试验材料,通过调查试验材料的生育期、干物质积累、叶面积变化和分蘖消长动态的测定,明确了拔节至抽穗期是水稻产量形成的关键时期;根据试验材料干物质积累的变化规律建立了干物质随时间变化的生长曲线,经检验拟合较好。     

Labor requirements of system of rice intensification (SRI) in Cambodia

Local governments, NGOs, system of rice intensification (SRI) adopters, and researchers in Cambodia have extensively discussed the SRI. Agreement on the benefits, however, remains elusive. Some claim SRI increases rice yields at lower costs; others state that the evidence is still inconclusive. The adoption and impact of innovations influenced by the most practical SRI principles, which adopters can and do implement, as well as other SRI labor requirement have yet to be comprehensively investigated. This study aimed at elucidating and comparing distinct aspects of SRI labor requirements and conventional practices that can lead to more intensive SRI adoption. A household survey and field observations were conducted in three rain-fed villages in the southern part of Cambodia: two in Kampot Province and one in Kampong Speu Province. Findings showed little or no difference between SRI labor requirements and conventional practices. Laborers are in high demand when preparing land and nurseries, transplanting seedlings, and harvesting. Rice farmers alone or hired laborers have generally proved sufficient to date. Hired labor costs depend on the supply of farmer-family labor and the efficacy of the “Sharing-hand” system, not on farming techniques per se. This system helps alleviate hired labor costs, one of the highest cost factors. The findings also indicated that the degree of SRI adoption shows no correlation between the home-to-plot distance and availability of farmer-family labor or hired labor. The key factors for improving the degree of SRI adoption are farmer zeal and careful attention rather than the home-to-plot distance and availability of labor.     

Dual-subtype FIV vaccine (Fel-O-Vax FIV) protection against a heterologous subtype B FIV isolate

Vaccine trials were undertaken to determine whether the Fel-O-Vax FIV, a commercial dual-subtype (subtypes A and D) feline immunodeficiency virus (FIV) vaccine, is effective against a subtype B FIV isolate. Current results demonstrate the Fel-O-Vax FIV to be effective against a subtype B virus, a subtype reported to be the most common in the USA.     

Developmental ability of somatic cell nuclear transferred embryos aggregated at the 8-cell stage or 16- to 32-cell stage in cattle

Aggregation of somatic cell nuclear transfer (SCNT) embryos in mice is reported to improve full-term development. In the present study, we attempted to improve the development of SCNT embryos by aggregation in cattle. In Experiment 1, to examine the effect of the timing of aggregation on in vitro development of cumulus-cell NT embryos, we aggregated two or three SCNT embryos (2X or 3X embryos) at the 1-cell, 8-cell and 16- to 32-cell stages. Irrespective of the timing of aggregation, 3X embryos developed to the blastocyst stage at a high rate. However, aggregation did not improve the total blastocyst formation rate of the embryos used. The cell numbers of 3X embryos aggregated at the 1-cell stage and 2X embryos tended to be higher than that of single NT embryos (1X embryos). Furthermore, a significant increase in cell number was observed in 3X embryos aggregated at the 8-cell stage and 16- to 32-cell stage. In Experiment 2, we used fibroblast cells as nuclear donors and examined in vitro development of 3X embryos aggregated at the 8-cell stage and 16- to 32-cell stage. As a result, 3X embryos had high blastocyst formation rates and higher cell numbers than 1X embryos, which was consistent with the results of Experiment 1. In Experiment 3, we examined the full-term developmental ability of 3X embryos aggregated at the 8-cell stage and 16- to 32-cell stage. After transfer of fibroblast-derived NT embryos into recipient animals, a significantly higher pregnancy rate was obtained on Day 60 in 3X embryos than in 1X embryos. Two embryos aggregated at 8-cell stage and one embryo aggregated at the 16- to 32-cell stage developed to term, while no pregnancies derived from 1X embryos that lasted to Day 60. However, two of the cloned calves were stillborn. These results suggest that aggregation of the 8-cell stage or 16- to 32-cell stage SCNT embryos may improve the pregnancy rate, but that it cannot reduce the high incidence of fetal loss and stillbirth, which is often observed in bovine SCNT.     

Effects of the fattening period on the fatty acid composition of fat deposits and free amino acid and inosinic acid contents of the longissimus muscle in carcasses of Japanese Black steers

The effects of the fattening period on carcass characteristics, fatty acid composition of fat deposits, and muscle free amino acid (FAA) and inosinic acid (IMP) contents were evaluated in Japanese Black steers. Ten castrated, 10-month-old calves derived from the same sire were divided into five to be slaughtered at the age of 30 months after a 20-month fattening period (20-month group) and five to be slaughtered at the age of 34 months after a 24-month fattening period (24-month group). Concerning the fatty acid composition of subcutaneous fat, the percentage of palmitoleic acid was higher ( P  < 0.05) in the 24- than in the 20-month group, but no difference was noted in any other fatty acids. For intermuscular fat, no difference was observed in any fatty acids. The percentages of oleic acid and total monounsaturated fatty acid of intramuscular and perinephric fat were higher ( P  < 0.05) in the 24- than in the 20-month group. Of the FAAs in the longissimus thoracis muscle, the threonine and tyrosine contents were lower ( P  < 0.05) in the 24- than in the 20-month group. The IMP content was higher ( P  < 0.05) in the 24- than in the 20-month group, suggesting an effect of prolongation of the fattening period.     

Tick infestation of sika deer (Cervus nippon) in the western part of Yamaguchi Prefecture,Japan

Ticks were collected from 94 sika deer (Cervus nippon) hunted in the western part of Yamaguchi Prefecture, Japan from August to November 1999, and March to July 2000. Haemaphysalis longicornis and H. yeni were the dominant species from April to August, while H. flava and H. megaspinosa were dominant in October, November and March. This is the first report of H. yeni in the mainland of Japan. Small numbers of H. kitaokai, Amblyomma testudinarium and Ixodes ovatus were also recorded.     

Serum amyloid A and haptoglobin levels in bovine amyloidosis

Serum amyloid A (SAA) and haptoglobin (Hp) levels were determined in 25 cows suffering from amyloidosis. SAA levels in cows with amyloidosis ranged between < 0.3 and 225.8 microg/ml, with a median level of 105.1 microg/ml, and Hp levels ranged between < 20 and 1860 microg/ml, with a median level of 950 microg/ml. These levels were significantly higher than the levels observed in healthy cows (SAA levels ranged from < 0.3 to 13.5 microg/ml, with median of 1.4 microg/ml, and Hp levels were undetectable in all cases), but were not significantly different from the levels observed in control cows with chronic inflammation. There was a significant correlation between SAA and Hp levels in cows with chronic inflammation , but not in cows with amyloidosis. It was concluded that the serum SAA levels in cows with amyloidosis might be changed by some factor other than inflammation.     

Molecular typing of Staphylococcus aureus isolated from bovine mastitic milk on the basis of toxin genes and coagulase gene polymorphisms

A total of 270 strains of Staphylococcus aureus, isolated from mastitic milk, were investigated by the polymerase chain reaction for the presence of genes encoding enterotoxins (sea to sej) and a toxic shock syndrome toxin (tst). One hundred eighty three (67.8%) bovine isolates possessed either one or more toxin genes and the most common pattern that coexisted in S. aureus was tst, sec, seg, and sei. Coagulase genotyping revealed 15 patterns, and 161 of the 270 isolates (59.6%) belonged to the coagulase genotype B1. Further, these 161 isolates possessed at least two enterotoxin genes. However, the role of these toxins in udder pathogenicity remains unclear. Moreover, the predominant isolate possessed the enterotoxin genes supporting the theory that superantigenic toxins are important for the udder pathogenesis.     

Responses of a beech (Fagus crenata Blume) stand to late spring frost damage in Morioka,Japan

Following two weeks of a warm period, beech trees at the study site began leafing. However, a spring frost occurred in the cold morning of April 21, 2001 (Day111, Julian day) and killed about 80% of the fresh leaves on a 40-year-old Siebold's beech (Fagus crenata Blume) stand in Morioka, Japan. Leaves emerged on sprouts from latent buds (latent leaves) 36 days after the frost. Field measurements between 1999 and 2003 revealed the following: (1) Leaf area index was about 4 in normal years and about 1.2 in 2001. (2) The elongation of latent leaves took 55 days about 40 days longer, and they matured about 30 days faster than normal leaves in regular years. (3) Photosynthetic capacities were similar between the latent leaves in 2001 and the normal leaves in 2002 at the top of the canopy. A longer leafing period, faster maturation and sustained photosynthetic capacity of the latent leaves would be helpful to reduce the impacts of frost damage on growth. (4) The frost damage greatly reduced NPP from about 2100 DW g m⁻² y⁻¹ in the previous two years to about 1000 DW g m⁻² y⁻¹ in 2001. However, NPP recovered almost completely (about 1800 DW g m⁻² y⁻¹) in 2002. (5) Seasonal NPP increased similarly in 2001 with other years before Day150 for 40 days after the frost, and decreased afterwards. Shoot elongation also stopped at approximately Day150 in normal years. These findings suggested that radial and height growth in the early growing season was supported by the storage of previous year photosynthesis. (6) A regression growth model was created using meteorological data from 1999 and 2000, and the model was applied to data from 2001 to estimate the potential growth under normal conditions. The ratio of measured and estimated NPP changed seasonally, greater than 0.4 between Day150 and Day210, but below 0.25 between Day210 and Day250. This suggests that beech allocated more photosynthetic products for the next year's growth rather than the current growth in the latter growing season, thereby achieving the same initial growth with other years and amazing recovery in 2002.