Evaluation of the progeny of third-generation Sydney rock oyster Saccostrea glomerata (Gould, 1850) breeding lines for resistance to QX disease Marteilia sydneyi and winter mortality Bonamia roughleyi     

John A Nell  & Ben Perkins 《Aquaculture Research》2006,37(7):693-700

A breeding program for Sydney rock oysters Saccostrea glomerata (Gould, 1850) has been selecting oysters for resistance to QX disease (Marteilia sydneyi) and winter mortality (Bonamia roughleyi) for three generations at three sites in Georges River, New South Wales, Australia. The experimental sites are located at the upper, middle and lower reaches of oyster growing areas in the estuary. QX disease mainly occurs in the middle and upper reaches and is most severe at the latter. Winter mortality on the other hand occurs mainly at the lower and middle reaches and is most severe at the former. Progeny of third‐generation Sydney rock oyster breeding lines were evaluated for resistance to both QX disease and winter mortality against a non‐selected control. Line 1, selected for QX disease resistance at the upper estuary site, had excellent resistance to one season of exposure to disease, but suffered high mortality during the second season of exposure. However, these oysters had already reached market size of 50 g whole weight, with low mortality at 2 years of age, before the second episode of QX disease. Line 2 showed good improvement in resistance to both diseases, whereas Line 3, was the most resistant to winter mortality. Selection for resistance to QX disease did not appear to confer resistance to winter mortality and the converse also applied.  相似文献   

NETWORK FLOWS,CUTS AND THEIR RELATIONS     

Li Shengjie Department of Natural Science 《保鲜与加工》1992,(2)

This paper first presents the indication functions ofcirculation flow,deviation and cut,and then studies the relatiomsbetween the indication functions of elementary circuit and cut,betweencirculation flow and cut,and between deviation and cut.  相似文献   

Substituting Ability of Individual Barley Chromosomes for Wheat Chromosomes 1. Substitutions Involving Barley Chromosomes 1, 3 and 6   总被引：1，自引：0，他引：1  

A. K. M. R. Islam  K. W. Shepherd 《Plant Breeding》1992,109(2):141-150

In order to determine the genetic relatedness of individual barley chromosomes to wheat chromosomes, ‘Betzes’ barley chromosomes 1, 3 and 6 were substituted for individual ‘Chinese Spring’ wheat chromosomes of homoeologous groups 7, 3 and 6, respectively. The substitution status of these lines has been confirmed using isozyme selective markers, chromosome pairing behaviour in F₁ hybrids between the substitution lines and the appropriate double ditelocentric stocks of wheat, and hybridization of cDNA probes to the genomic DNA digests of these substitution lines. Each of the three barley chromosomes provided genetic compensation for the wheat chromosomes they replaced in the substitution plants. From the basis of this compensation with respect to plant vigour and fertility, barley chromosomes 1, 3 and 6 have been designated 7H, 3H and 6H.  相似文献   

江西省农产品地理标志保护研究   总被引：6，自引：5，他引：1  

卢慧  李庆  魏建美  黄芳  许晶晶 《江西农业学报》2013,(12):133-136

自地理标志保护制度实施以来,我国的农业产业化发展速度加快,农产品市场竞争力得到提高,农业增效农民增收十分明显。以江西省的农产品地理标志保护作为研究对象,在查阅文献、收集数据的基础上,从农产品地理标志的注册数量、使用量、名特优标志数量以及产值等方面展开了分析,发现目前运用地理标志制度保护农产品及农民权益过程中存在的问题,进而提出了相应的对策措施,以期为江西省的农产品地理标志保护提供理论指导和现实借鉴。  相似文献   

The impact of community-based forest management on timber treeregeneration in north-eastern Honduras,with specific reference tobig-leaf mahogany (Swietenia macrophylla)     

《Southern Forests》2013,75(3-4):133-140

Reduced-impact logging is used to minimise the negative effects of selective logging. However, it has been suggested that low-impact logging may create too little disturbance for the regeneration of the light-demanding timber tree species, hence compromising forest productivity. This study evaluates the impact of low-intensity, non-mechanised, certified community forest management on timber tree regeneration. Particular attention was paid to big-leaf mahogany (Swietenia macrophylla), which has a regeneration pattern linked with large-scale disturbances. Logging gaps were compared to natural treefall gaps of an unlogged forest. There were more species of the light-demanding timber trees, but fewer individuals of the shade-tolerant timber species in the certified forest logging gaps, compared to unlogged forest treefall gaps. Furthermore, significant differences were found in the environmental characteristics of the logging and natural treefall gaps, although these only partially explained the differences in timber regeneration. Mahogany was found in over half of the logged forest gaps, whilst being nearly absent in the natural treefall gaps. However, all mahoganies in the established logging gaps were seedling-sized, indicating that regeneration may be hampered due to competing vegetation. The results of the study suggest that low-impact forest management may, at least in the short term, favour light-demanding species over the shade-tolerant ones, similarly to conventional forest management.  相似文献   

The rapid determination of nitrate at low concentrations in soil extracts: Comparison of ion‐selective electrode with continuous‐flow analysis     

《Communications in Soil Science and Plant Analysis》2012,43(12):1437-1451

Abstract

The efficiency of extraction of nitrate with saturated CaSCO₄ solution and with IM KCl was compared for a range of field‐moist and air‐dried soils. Saturated CaSO₄ was as effective for moist soils and slightly more effective for dried ones, and removed 95% of the nitrate after shaking for 5 min. Three methods of nitrate analysis using an ion‐selective electrode were compared with continuous‐flow analysis (CFA). All gave good correlations with CFA but only one, a “known addition” method, gave results which agreed quantitatively. This method could be applied at nitrate‐N concentrations at least as low as 0.5 mg kg^‐1.  相似文献   

不同稻田综合种养模式下杂草长期控制效果的调查   总被引：1，自引：0，他引：1  

张峥  卜德孝  强胜 《植物保护学报》2022,49(2):693-704

为明确稻田综合种养模式是否可以长期有效控制杂草危害,通过对江苏省48个样点共6种综合种养模式(稻鸭、稻蟹、稻虾、稻鱼、稻鳖和稻鳅/鳝共作)农田的杂草群落和土壤种子库进行调查,比较分析杂草群落综合草情优势度、物种多样性以及杂草群落和土壤种子库的组成和变化。结果表明,在综合种养模式实施1~3年,杂草群落综合草情优势度和土壤种子库密度均明显下降,其中稻鸭共作模式下两者均下降最多,其次是稻虾共作模式下杂草群落综合草情优势度下降较多,而稻鱼共作模式下土壤种子库密度下降较多。实施4~5年,各种养模式下杂草群落综合草情优势度和土壤种子库密度均上升,草害加剧,杂草防控效果下降;其中稻鳅/鳝共作模式下杂草群落综合草情优势度和土壤种子库密度与常规稻田相比升幅最大,分别上升28.8%和25.3%;由于稻鳖、稻鳅/鳝共作模式实施均未超过5年,在实施4~5年时整体上杂草危害最为严重,禾本科杂草、阔叶杂草以及莎草科杂草的综合草情优势度较常规稻田分别上升42.4%、12.3%、0.7%和31.5%、27.7%、38.1%。实施5年以上,稻鸭共作模式下阔叶杂草的综合草情优势度较常规稻田下降65.0%,但禾本科杂草的综合草情优势度和土壤种子库密度较常规稻田分别上升80.5%和66.6%,成为杂草群落和土壤种子库的优势种群;稻虾共作模式下莎草科杂草和阔叶杂草的综合草情优势度较常规稻田分别上升17.8%和45.0%;稻蟹共作模式下莎草科杂草、阔叶杂草和禾本科杂草的综合草情优势度较常规稻田分别上升22.7%、35.3%和29.0%。表明当长期实施同种稻田综合种养模式时,杂草群落在单一的选择压力下会加快演替,杂草危害均呈先降后升的变化趋势,不利于田间杂草的长效防控,建议实施针对耗竭土壤种子库的综合技术措施。  相似文献   

不同因素影响下棉田土壤中大丽轮枝菌微菌核的数量特征     

刘海洋  王伟  张仁福  温切木·阿布列孜  姚举 《新疆农业科学》2021,58(3):522-531

【目的】 土壤中大丽轮枝菌的微菌核是棉花黄萎病发生的关键因子,研究外界因素对土壤中微菌核数量的影响特征,为棉花黄萎病的防治提供参考意义。【方法】 利用选择性分离培养与荧光定量PCR技术,检测采自新疆棉花黄萎病田内不同处理组土壤中的微菌核,并结合室内盆栽试验进行验证。【结果】 大丽轮枝菌微菌核在棉田土壤中呈聚集分布,不同抗病性棉花品种根围微菌核的数量无明显差异。花铃期时'新陆中66号根围微菌核的数量显著高于新稻11号,至吐絮期时新稻11号根围微菌核数量显著增加,与新陆中66号根围相比已无显著差异。耐病品种中植棉2号以及中植棉2号＋新稻11号混种处理土壤中微菌核数量与感病品种军棉1号及军棉1号+新稻11号混种处理均无显著差异。水淹20~30 d时土壤中微菌核的数量显著上升,至60 d土壤中微菌核数量略下降,至150 d时微菌核数量升至最高,是初期微菌核数量的5倍;种稻处理土壤中微菌核的消长动态与对照一致,至150 d时微菌核数量是初期的8倍。【结论】 大丽轮枝菌微菌核在土壤中聚集分布,其数量与棉花品种的抗病性无明显相关,大田种植旱稻前期能延缓微菌核的增长。盆栽水淹能够显著促进土壤中微菌核数量的增长,种稻未能抑制甚至促进了土壤中微菌核数量的增长。  相似文献   

杀虫杀螨剂对柑桔全爪螨和腹管食螨瓢虫的选择毒性     

宋寿龄  陈达荣  伍洲  黄光环  黄活泼 《福建农林大学学报(自然科学版)》1988,(4)

室内测定结果表明,8种杀虫杀螨剂对柑桔全爪螨和腹管食螨瓢虫的成虫与幼虫的毒性,以双甲脒对柑桔全爪螨雌成螨的药效最高;三氯杀螨醇、机油乳剂和柴油乳剂对腹管食螨瓢虫成虫有选择作用,三氯杀螨醇、杀虫脒、普特丹和双甲脒对腹管食螨瓢虫幼虫(三龄)有选择作用,其中双甲脒选择作用最高,对腹管食螨瓢虫最为安全。柴油乳剂对腹管食螨瓢虫幼虫敏感,而水胺硫磷对腹管食螨瓢虫成虫和幼虫均较敏感。在常用三氯杀螨醇和杀虫脒的老果园,因害螨产生抗药性,对食螨瓢虫幼虫失去了选择作用,其毒性比均在1.0以下。  相似文献   

植物源杀虫剂对椰心叶甲和椰甲截脉姬小蜂的安全性评价     

吕朝军  钟宝珠  李洪  孙晓东  马子龙 《广东农业科学》2011,38(6):80-81

采用叶片浸渍法和药膜法测定了4种植物源杀虫剂对椰心叶甲和椰甲截脉姬小蜂的毒力,比较了药剂在二者之间的毒力选择性.结果表明,供试杀虫剂中以印楝素和苦参碱对椰心叶甲和椰甲截脉姬小蜂的选择性最高,其选择性比值(LC50椰甲截脉姬小蜂/LC50椰心叶甲)为0.4856和0.4597;.烟碱虽然对椰心叶甲的毒力较高,LC50为9...  相似文献