农牧交错带退耕还草对土壤淀粉酶和脲酶活性的影响

在农牧交错带以小麦为对照,研究退耕还草对0～20cm土壤淀粉酶和脲酶活性的影响.结果表明:退耕还草后,草地土壤淀粉酶和脲酶活性都显著高于小麦地;冰草和无芒雀麦草地土壤淀粉酶活性和脲酶活性最高;老芒麦+冰草(1∶3)对改善土壤淀粉酶的效果较好;老芒麦+冰草(1∶1)提高土壤脲酶活性的作用较大;随着利用年限的增加,老芒麦草地土壤淀粉酶活性和脲酶活性均呈先增加,后降低的趋势.     

中国北方农牧交错区研究展望

近年北京和华北地区的沙尘灾害天气引起了广泛关注,其上风向地区的农牧交错区不但是防护的重要屏障,也是沙尘的源地之一。为了减轻农牧交错区本身的生态压力和环境恶化,需要明确其范围、界线、发展历史和治理方式。综述了上述中国北方农牧交错区的研究进展,并展望了农牧交错区研究中比较紧迫的区域和研究方向。在研究的领域当中,荒漠化及物质迁移仍然是持续研究的基础,景观（土地利用）变化及其模拟和水土保持等生态恢复研究是针对性较强的研究内容;在农牧交错区中,河北坝上地区和内蒙古乌盟后山、长城沿线、毛乌素和科尔沁等农牧交错地带是重     

我国棉枯萎镰刀菌生理小种变异监测研究

对1986～1997年在我国10个主要产棉省（区）采集的84个棉枯萎镰刀菌代表菌系进行了致病力测定。结果表明：总体上生理小种类型和分布与1985年报道的基本相同,仍为第3、7、8号3个小种,其中7号小种占83.3%,是我国毒力强的优势小种,广泛分布于我国各大棉区;3号和8号小种分别局限于新疆吐鲁番地区和湖北新州地区。同时发现局部地区有些菌系出现了变异,特别是1991～1994年采集的3号小种5个菌系出现了对鉴别寄主萨克尔的致病力明显减弱的变异型。鉴于国际通用的鉴别寄主中的所有棉属寄主均被7号小种菌系高度感染,不能明显区分不同菌系间的致病力强弱,笔者增加了我国抗、感性不同的棉属辅助鉴别寄主,并改用病情指数划分棉属鉴别寄主3个反应型（R,W,S）,依据平均病指大小将7号小种内的菌系分为强、中、弱3个类群。     

A six week screening method for mechanisms of host plant resistance to Diuraphis noxia in wheat accessions

The Russian wheat aphid Diuraphis noxia (Kurdjumov) is a serious pest of wheat in South Africa. The use of D. noxia-resistant cultivars may reduce the impact of this pest on wheat production and at the same time reduce environmental risks and control costs. The mechanisms of resistance in two new sources of resistance were compared by using various methods, in order to establish a rapid and relatively accurate screening protocol. The resistant lines OSU ID 2808 and Aus 22498 were compared to the susceptible cultivars Betta and Tugela. The predominant mechanism of resistance in OSU ID 2808 was antibiosis, although a low level of antixenosis may also be present. The line Aus 22498 was primarily a tolerant type, with a moderate level of antibiosis and a low level of antixenosis. A six week screening procedure is described using the colony count technique for antibiosis, a completely random free choice experiment for antixenosis and a three week test measuring initial and final plant height, initial and final D. noxia infestation, damage rating, leaf area and dry plant mass for tolerance. This revised version was published online in July 2006 with corrections to the Cover Date.     

Inoculation of micropropagated plantlets of Eucalyptus tereticornis with ectomycorrhizal fungi

Micropropagated plantlets of Eucalyptus tereticornis at the root initiation stage were inoculated in vitro with Amanita murina, Hysterangium incarceratum, Laccaria laccata, Pisolithus tinctorius (3 isolates), Scleroderma cepa and S. flavidum in order to select the most compatible ectomycorrhizal partner. H. incarceratum and the two Scleroderma species did not form mycorrhizas with E. tereticornis. Two local isolates of P. tinctorius formed significantly more mycorrhizas than the other isolates tested. Plantlets with mycorrhizas formed by one of the local isolates of P. tinctorius were transplanted to the nursery where their growth significantly exceeded that of non-mycorrhizal plants.     

Combining ability for beet armyworm, Spodoptera exigua, resistance and horticultural traits of selected Lycopersicon pennellii-derived inbred backcross lines of tomato

Ten selected inbred backcross lines (IBL), from a Lycopersicon esculentum cv.‘Peto 84’×Lycopersicon pennellii IBL population, with resistance to beet armyworm (BAW), Spodoptera exigua, higher fruit mass and fruit yield, were crossed with eight elite cultivated L. esculentum inbred lines in a Design II mating design. Three elite inbreds were also crossed to ‘Peto 84′, the IBL recurrent parent, as a control for combining ability. Field plots of all resulting F₁ progenies and control cultivars were inoculated with BAW eggs and evaluated for resistance to BAW, fruit mass, fruit yield, vine size and maturity at three field locations. Reductions in fruit damage by BAW were found in four of the 10 IBL F₁ progenies. Significant male and female general combining ability (GCA) estimates for BAW resistance were observed, but significant specific combining ability for BAW resistance was not detected. The fruit mass of F₁ hybrids was significantly lower than large-fruited controls, but was not significantly different from elite inbred by ‘Peto 95’F₁ hybrids. Selection based on inbred performance identified IBL with positive GCA for BAW resistance and yields in Design II hybrids. BAW resistance in the 09 selected IBL and IBL- derived F₁ progeny was associated with two undesirable traits, later maturity and larger vine size. Index selection of IBL was more effective at identifying IBL with positive GCA for fruit mass and fruit yield than GCA for BAW resistance.     

Morphology, host range and phylogenetic diversity of Sphingomonas phages in the floodwater of a Japanese paddy field

Members of the Sphingomonas -related genera ( Sphingomonas , Sphingobium , Novosphingobium and Sphingopyxis ) are dominant in bacterial isolates from the floodwater of Japanese paddy fields. Fifty-eight Sphingomonas / Novosphingobium bacteriophages (phages) were isolated to elucidate their morphology, host range and phylogenetic diversity based on the capsid gene ( g23 ) sequence. All of the phages were siphoviruses with isometric or elongated, icosahedral capsids and a long, non-contractile tail. The genomes were double-stranded DNA measuring either 40, 60, 100 or 160 kb. The host range of the phages was examined by infecting 16 bacterial isolates from the floodwater, belonging to Sphingomonas , Novosphingobium , Sphingopyxis and Porphyrobacter . The host range was widely different and varied between infection of only the host used for isolation and infection of hosts belonging to the three genera of Sphingomonas , Novosphingobium and Porphyrobacter . All phages had g23 , indicating the ubiquity of the g23 gene among Myoviridae and Siphoviridae members. Every g23 sequence of the phages belonged to one of the six uncharacterized Paddy Groups proposed by Fujii et al . (2008 ). The g23 sequences were identical at the nucleotide level for several phages with isometric and elongated capsids with 60 and 160 kb genomes, and between some phages and the clones that were retrieved from distant paddy fields. This indicates the common occurrence of horizontal transfer of g23 in the paddy fields. The g23 sequence does not correlate with the host range of those phages. In addition, a larger degree of divergence of g23 from coliphage T4 in paddy fields compared to marine environments was estimated from the present study.     

甘薯改良式贮藏库设计与贮藏效果

改良式贮藏库是在原有甘薯高温屋窖的基础上,结合节能日光温室结构改建而成,该贮藏库增设了节能缓冲间,采用复合异质墙体和外部增加防寒沟,经温度等效应分析和贮藏试验分析,适合甘薯的长期贮藏。该库贮藏甘薯144天后,好薯率为94．8％,硬度为60．61kg／cm^2,其它指标均好于对照组。     

石榴根际寄生线虫的种类研究

2003~2006年,对云南省主要石榴产区蒙自县、会泽县和建水县的石榴寄生线虫进行了采样调查,采用形态特征进行鉴定。结果表明,寄生于云南石榴根际的线虫有15属12种,其中有11个种是寄生石榴的新记录种。     

不同寄主植物对柳蓝叶甲生长发育的影响

为明确不同寄主植物对柳蓝叶甲生长发育产生的影响,本研究在室内条件下[(27±1.0)℃,12D:12L],以杨树、柳树和桑树叶片饲养柳蓝叶甲,结果表明,不同寄主植物对柳蓝叶甲幼虫的发育历期和雌成虫的产卵行为有影响。取食柳树叶的柳蓝叶甲幼虫发育历期长于取食杨树叶的处理,卵孵化率和羽化率也较高;雌成虫在杨树叶上的产卵时间长于柳树叶,但相同条件下雌成虫产卵优先选择柳树叶;试验条件下柳蓝叶甲成虫、幼虫均不取食桑叶;无论取食何种寄主植物,雌成虫大都将卵成块产于幼嫩叶片背面。