Improving management for higher reproduction accelerates genetic improvement in closed herd of swine

The present study compared responses to selection at different conception rates and litter sizes at weaning in a simulated closed herd in a swine breeding program. The base population consisted of 10 males and 50 females, and 10 generations of selection was practiced by using individual phenotype or best linear unbiased prediction of breeding values for a trait with heritability (h²) of either 0.2 or 0.5. The probability of conception in a single mating was assumed to be 0.8, 0.9 or 1.0. Litter size at weaning was sampled randomly from a normal distribution with mean 8, 10 or 12 and variance 8.1225. Genetic response increased by approximately 6% for h² = 0.2 and approximately 5% for h² = 0.5 at generation 10 when conception rate was increased from 0.8 to 1.0. However, litter size at weaning did not affect response to selection. In conclusion, improving conception rate by environmental management increases genetic response indirectly in a breeding program of a closed swine herd.     

The effect of sowing date, stale seedbed, row width and mechanical weed control on weeds and yields of organic winter wheat

Three field experiments were carried out in organically grown winter wheat in Denmark. The treatments were sowing time (normal or late sowing) and false seedbed, row width (12 and 24 cm) and weed control method [untreated; mechanical weed control (weed harrowing at 12 cm supplemented with inter‐row hoeing at 24 cm); and herbicide weed control]. Weed biomass in midsummer was greatest on plots sown at the normal sowing time (compared with delayed sowing) and was reduced by mechanical or chemical weed control (compared with untreated plots). Row width alone had no influence on weed biomass, but in the experiment with high weed pressure, the more intensive mechanical weed control used at a row width of 24 cm reduced weed biomass. Normal sowing time tended to give higher yields, but this was only statistically significant in one of the three experiments. Wide rows gave a yield decrease in the experiment with low weed pressure. The effect of weed control on yield was dependent on the weed pressure. At low weed pressure, mechanical weed control caused a yield decrease compared with untreated or herbicide treated. At intermediate weed levels there were no differences, whereas at high weed pressure, mechanical weed control and herbicide treatment caused a yield increase compared with untreated. False seedbeds were shown to contribute to a decrease in the soil seed reserve.     

Trichoderma Biocontrol of Colletotrichum acutatum and Botrytis cinerea and Survival in Strawberry

Trichoderma isolates are known for their ability to control plant pathogens. It has been shown that various isolates of Trichoderma, including T. harzianum isolate T-39 from the commercial biological control product TRICHODEX, were effective in controlling anthracnose (Colletotrichum acutatum) and grey mould (Botrytis cinerea) in strawberry, under controlled and greenhouse conditions. Three selected Trichoderma strains, namely T-39, T-161 and T-166, were evaluated in large-scale experiments using different timing application and dosage rates for reduction of strawberry anthracnose and grey mould. All possible combinations of single, double or triple mixtures of Trichoderma strains, applied at 0.4% and 0.8% concentrations, and at 7 or 10 day intervals, resulted in reduction of anthracnose severity; the higher concentration (0.8%) was superior in control whether used with single isolates or as a result of combined application of two isolates, each at 0.4%. Only a few treatments resulted in significant control of grey mould. Isolates T-39 applied at 0.4% at 2 day intervals, T-166 at 0.4%, or T-161 combined with T-39 at 0.4% were as effective as the chemical fungicide fenhexamide. The survival dynamics of populations of the Trichoderma isolates (T-39, T-105, T-161 and T-166) applied separately was determined by dilution plating and isolates in the mixtures calculated according to the polymerase chain reaction (PCR) using repeat motif primers. The biocontrol isolates were identified to the respective species T. harzianum (T-39), T. hamatum (T-105), T. atroviride (T-161) and T. longibrachiatum (T-166), according to internal transcribed spacer sequence analysis.     

高速公路边坡防护体系的建植养护

在对广东省普惠高速公路边坡生物防治体系——护坡草皮的建植和养护过程中，就草种选择、建植方式和质量监控等问题进行了讨论并提出建议，旨在提高我国高速公路边坡防护体系草皮的建植和养护水平。     

春季休牧对草原和家畜生产力的影响

从4月上旬到6月下旬,在内蒙古锡林郭勒典型草原,进行春季休牧试验,对休牧和非休牧的草原进行生产力监测.结果表明:春季休牧可以有效地保护草原生态环境,经过两个月休牧后,草原植被状况明显改善;休牧期间采用低投入维持性饲养,可以显著降低饲养成本.并对休牧措施的生态效益、生产实践可行性和经济合理性进行综合讨论和评价.     

西尼罗热病毒RT-PCR检测方法的建立

参考Genebank发表的西尼罗热病毒(West Nile virus，WNV)E糖蛋白基因序列，自行设计合成一对引物，对WNV进行RT—PCR扩增，产物经琼脂糖电泳分析，呈现一条约400bp的条带，将其克隆入pMD18-T—Vector载体中，并进行序列测定，与已发表的WNV基因比较发现，核苷酸的同源性为99．7％，证实为WNV的E基因，通过对样品多次检测，都能扩增出一条约400bp的条带，表明该方法比较稳定。     

土壤易氧化有机碳与溶解性有机碳对荒漠草地沙漠化过程中土壤碳库变异的表征

以干旱、半干旱地区荒漠草地不同沙漠化阶段土壤为研究对象,研究不同沙漠化阶段土壤易氧化有机碳与溶解性有机碳含量和分配比例变异规律,分析不同沙漠化阶段土壤碳库指数变化,探讨荒漠草地沙漠化过程中土壤易氧化有机碳与溶解性有机碳对土壤碳库的表征作用。结果表明,随着荒漠草地沙漠化程度的加剧,易氧化有机碳含量表现出一定的波动性,但整体呈下降趋势,溶解性有机碳含量呈线性下降。易氧化有机碳和溶解性有机碳分配比例均在荒漠草地达到最大值,在半固定沙地达到最小值。利用易氧化有机碳含量计算的土壤碳库管理指数随荒漠草地沙漠化程度增加表现出先下降后上升趋势,利用溶解性有机碳含量计算的土壤碳库管理指数呈线性下降趋势。易氧化有机碳、溶解性有机碳含量与土壤有机碳均显著正相关,但溶解性有机碳的相关系数略高于易氧化有机碳。通过比较活度敏感指数和碳库管理指数敏感指数发现,荒漠草地逆向演替至固定沙地过程中,易氧化有机碳的各项敏感指数均高于溶解性有机碳。固定沙地演替至流动沙地过程中,溶解性有机碳的各项敏感指数均高于易氧化有机碳,表明易氧化有机碳能够较好地表征荒漠草地沙漠化前期土壤碳库变化,而荒漠草地沙漠化中期和后期利用溶解性有机碳表征效果更好。     

水氮供应对地下滴灌紫花苜蓿生长特征及草地小气候的影响

为探讨不同水氮处理条件下紫花苜蓿生长状况与草地小气候特征的关系,以2年生紫花苜蓿“巨能7号”为研究对象,采用田间试验和室内分析相结合的方法,研究了宁夏引黄灌区地下滴灌条件下不同滴灌量和施氮量处理下紫花苜蓿生长特征和草地小气候的变化。结果表明:1)滴灌量和施氮量对紫花苜蓿的株高、叶面积和鲜草产量都有显著的影响,表现为紫花苜蓿的株高、叶面积和鲜草产量均随滴灌量和施氮量的增加而增加,当施氮量增加到一定值时,继续增施氮肥,其鲜草产量增产效果在不同滴灌量处理下表现出不同的趋势。2)与不施氮处理相比,增施氮肥降低了紫花苜蓿株间空气温度、浅层土层温度和株间光照强度,而增加了群体内部空气相对湿度。3)不同滴灌量对紫花苜蓿的生长微环境的调节作用不同,随着滴灌量的增加,紫花苜蓿群体相对湿度逐渐提高,而紫花苜蓿株间气温和浅层土层温度降温效应越明显。4)紫花苜蓿生育期间株高与叶面积、草产量和群体内部相对湿度呈极显著正相关(P<0.01),与群体内光照强度、株间气温、浅层土壤温度呈极显著负相关(P<0.01)。合理减少滴灌量和施氮量不仅能维持紫花苜蓿良好的生长特征,而且能提高鲜草产量和改善草地生态环境条件。本研究旨在为紫花苜蓿群体微环境生态因子的改善及高产优质栽培措施提供科学依据。