Hydrolysis of terbufos using simulated environmental conditions: rates, mechanisms, and product analysis.

This study focuses on the hydrolysis of terbufos, an organophosphorus pesticide. Combining GC-MS and wet chemistry methods, di-tert-butyl disulfide and formaldehyde were identified and quantified as major degradation products. Diethyl dithiophosphate was also indirectly identified as a degradation product under alkaline conditions. Hydrolysis rate constants of terbufos under homogeneous conditions were comparable to those of phorate and show relative insensitivity to pH under slightly acidic to neutral pH conditions, as the observed rate constants varied only in the range of (4.5-5.0) x 10(-6) s(-1) between pH 5.7 and 9.4; neutral hydrolysis is thus the most dominant hydrolysis pathway of terbufos in ambient waters. The mechanisms for terbufos hydrolysis and the formation of the major products and their temporal profiles are discussed. To assess the environmental impact of degradation products of this widely used pesticide, Microtox was used to analyze the toxicity of terbufos and two of its degradation products: diethyl dithiophosphate and di-tert-butyl disulfide; the EC(50) of terbufos was found to be >17 microM, whereas the EC(50) of di-tert-butyl disulfide was 1.3 microM.     

全国农业血防电脑应用与地理图形系统（NYXF）的研制

“全国农业血防电脑应用与地理图形系统（ＮＹＸＦ）”是新兴科学领域内的一门新技术。它是电脑技术与卫生防疫，农业生态，畜牧兽医技术经济，农业技术经济，畜牧饲养和兽医等多种学科相结合，将管理，数据库，报表和图形等浑于一体，能进行农业血防管理技术经济若干指标体计算；可对农业血防开发项目投资效果提供动态数据，图表和辅助分析。并能将农业血防信息数据库与地理图形有机地结合在一起，从而打破了关系型数据库系统单纯依     

Diversity and adaptation in rice varieties under static (ex situ) and dynamic (in situ) management

This study compares genebank-conserved and farmer managed populations of the same farmers' varieties of rice. Seven varieties that had been collected twice, in the early 1980s and in 1991, were recollected in 1997 after having been grown continuously in farmers' fields. Since the first genebank collection, rice cultivation in the Meking delta has been intensified with a rather abrupt switch from single to double cropping, more use of chemical fertilisers, improved water management, and more market oriented production. Many farmers' varieties have been maintained as a second crop but with a considerably delayed planting time compared to previous practice. In this experiment, the ex situ materials represent adaptation to pre-intensification conditions while the in situ populations have been exposed to the intensive production system for a number of years. The materials were tested in the wet season of 1997 under current farmers' management practices in an on-farm field experiment within the area where the varieties originated. Agronomic, stress resistance and morphological traits and variation at 7 isozyme loci were observed in the field or laboratory. Analysis of variance (ANOVA) and Principal Component Analyses (PCA) were used to study differences in agronomic and morphological traits between ex and in situ populations. Isozyme variation was analyzed by Nei's diversity indices and Wright's F-statistics. Farmer-managed populations showed a general trend of later flowering and maturity time, more uniformity of grain quality, lower frequency of undesired off-types, and reduced drought stress tolerance compared with corresponding ex situ populations. There were no significant differences in grain yield or tolerance to biotic stresses. Allelic frequencies of isozymes showed no consistent differences that could be related to changes of the farming system. These results are interpreted as an adaptation to the changed farming system and include natural and farmers' selection for maturity time (all varieties are photoperiodic)and market standards. The poorer drought tolerance may reflect the fact that such stress was common before intensification but is not normally a factor under the current water management regime. For in situconservation strategies this case sheds some light on the survival of allelic diversity vs. adaptedness. Isozyme data indicate maintenance of allelic diversity. Adaptedness, however, is at risk under on-farm conservation. Natural and intentional selection will normally not remain constant over time. Consequent genetic changes include loss of adaptation to past conditions and building up of adaptation to new. In this case such changes have happened surprisingly fast. However, changes are limited to adaptation to factors of the environment and to market-relevant quality traits. Yield seems to be unaffected. Considering needs for crop improvement this case has kept the materials `updated' with respect to adaptation and unchanged with respect to yield potential. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effect of Plant Age and Humidity on Development of Bacterial Wilt of Forage Grasses

Abstract

The effect of plant age on the development of bacterial wilt of forage grasses was studied by dipping cut roots of Lolinm perenne L. cv. ‘Svea’ in a suspension of Xanthomonas campestris pv. graminis. The effect of humidity on disease development was studied by cutting leaves with scissors dipped in inoculum, and by spraying inoculum onto unwounded leaves. Young plants were more susceptible to the pathogen than old ones. X.c.graminis was easily isolated from young leaves and tillers, especially from the leaf bases. Disease symptoms were most severe at low humidity. However, high humidity is necessary for infection to take place through stomata and hydathodes.     

Effect of Semen Collection Methods on the Quality of Pre‐ and Post‐thawed Bali Cattle (Bos javanicus) Spermatozoa

This study was conducted to evaluate the response of Bali bulls (Bos javanicus) to different semen collection methods and their effects on fresh and post‐thawed semen quality. The collection methods employed were electro‐ejaculation (EE), transrectal massage (RM) and RM followed by EE (RM + EE). A total of 25 untrained Bali bulls (age between 2 and 4 years old) were subjected to the different semen collection methods. Fresh semen samples from all the 25 bulls were evaluated for volume, pH, general motility, live/dead ratio and abnormality using the conventional method. For fresh and frozen samples collected by EE and RM from 10 bulls, computer‐assisted semen analysis system was used for precise quantitative measurement of motility, velocity and forward progression. Accucell photometer was used to measure sperm concentration in all samples, regardless fresh and frozen. Semen samples were obtained 100% of the attempts using EE, 84% using RM and 96% using RM + EE. There were no differences among the collection methods for fresh semen quality characteristics, including motility, morphology and viability, but pH and volume were higher for EE than RM and RM + EE. Higher sperm concentration was observed in semen collected by RM than the other two methods. Different age groups (2–3 and >3–4 years old) of the bulls did not show significant differences in volume, pH, sperm concentration, percentages in motility, live/dead ratio and normal sperm morphology. The quality of semen for general and progressive motility, VAP, VSL and VCL and acrosomal integrity after thawing was higher for RM than EE. In conclusion, Bali bulls appeared to respond best to EE and the combination of RM + EE than RM, as a method of semen collection, with a shorter time of stimulation required. Differences in age of the Bali bulls did not affect the semen quality.     

高寒草地放牧系统钼的季节变化及盈缺分析

对青海省三角城种羊场高寒草地夏(6月中旬)、秋(9月中旬)、冬(12月中旬)三季的水、土壤、牧草以及绵羊被毛、肝脏、粪中钼含量进行了调查采样分析.结果表明,土壤中钼除夏季与我国正常水平(0.17mg/kg)一致外,秋冬两季均较低;牧草中的钼为夏季>秋季>冬季,但均低于正常水平(1.00mg/kg);绵羊被毛中钼夏季高于正常值,而秋冬两季严重缺乏且与三季绵羊肝钼状况一致,都表现出与牧草相同的季节变化规律,即夏季>秋季>冬季.因此,青海三角城种羊场绵羊处于低钼的生态环境与营养状况.     

白刺夜蛾发育起点温度与有效积温的研究

在甘肃荒漠草原对专白刺的猖獗害虫白刺夜蛾的发育起点温度与有效积温进行了研究,结果表明,卵期Ｃ＝１３．２±１．６（℃）,Ｋ＝１１５．４±１６．７（日度）;幼虫期Ｃ＝１７．５±１．５（℃）,Ｋ＝１６１．１±２８．３（日度）,蛹期Ｃ＝１７．５±２．３（℃）,Ｋ＝１１１．７±２７．７（日度）。     

Comparative analysis of local and improved practices used by farmer seed production schools in Vietnam

Farmer seed production schools in combination with participatory field experimentation might be effective instruments to enhance the skills of farmers to produce high-quality seed in the informal seed system in Vietnam. Four hundred twenty nine, unreplicated on-farm experiments were carried out in four different provinces and analyzed by the farmer seed production schools. These experiments consisted of two adjacent seed production plots: one with common local practice and one with improved practice. Differences between the two plots in yield and profit were assessed. Averaged across provinces, yields of the “improved practice plots” were 0.43 Mg ha⁻¹ higher in the wet season and 0.78 Mg ha⁻¹ higher in the dry season than the “local practice plots”. In the Nam Dinh and Nghe An provinces more hills per m², more input of potassium and muck, and fewer seedlings per hill at transplanting contributed to the higher yields in the “improved practice plots”. In the provinces Binh Dinh and Dong Thap, using a drum seeder for sowing, reduced seed rate, less input of nitrogen fertilizer and more potassium contributed to the yield advantage of the “improved practice plots”. The profit of the improved practice plots was 212 US$ ha⁻¹ higher than the profit in the local practice plots. Rice growers can benefit from lower seed rates, better yields and higher prices when grains are sold as seeds. These findings may direct the seed policies and extension approaches in Vietnam.     

A fresh weight-based method for evaluating soybean resistance to red crown rot

Soybean red crown rot (RCR) caused by Calonectria ilicicola is a serious soil-borne disease affecting soybean production and quality. The current visual necrosis-based method for the measurement of RCR severity is prone to subjectivity as well as time consuming and laborious as it requires digging out and washing the roots to remove adhering soil prior to the visual scoring. Using cultivar Enrei, we show that, upon C. ilicicola infection, relative fresh weights (RFW; fresh weights relative to non-inoculated control plants) showed a significant negative correlation with visual RCR severity in apical shoot (trifoliate and above, R² = 0.96), shoot (unifoliate and above, R² = 0.82) and roots (R² = 0.89). Furthermore, apical shoot RFW efficiently correlated with varying levels of C. ilicicola resistance in two test sets containing 37 soybean cultivars and three wild soybean accessions, exhibiting a significant correlation with visual severity (R² = 0.72 and 0.79, p < 0.01). Taken together, our results suggest that RFW can serve as an index of soybean RCR severity, providing a simple, rapid, consistent, and cost-effective method for evaluating C. ilicicola resistance in soybeans.