转基因玉米试管苗移栽影响因素及移栽技术要点

在海南省三亚地区,通过转基因技术获得规模化的转基因玉米试管苗的移栽成活率往往不高,这主要由其自身条件和外界环境引起的。该研究探讨了影响三亚地区转基因玉米试管苗移栽成活率的因素及移栽技术要点,为提高试管苗在三亚地区的移栽成活率提供参考依据。     

Evaluating eddy covariance method by large-scale weighing lysimeter in a maize field of northwest China

Accurate determination of evapotranspiration (ET) is useful to develop precise irrigation scheduling. Although eddy covariance (EC) is a direct method which is widely used to measure ET, its performance in arid region of northwest China is not clear. In this study, ET measured by EC (ET_EC) was compared with that by large-scale weighing lysimeter (ET_L) during the whole growing season of maize in 2009. Energy balance ratio was 0.84 for daytime fluxes, indicating that lack of energy balance closure occurred, so daytime ET_EC was adjusted by Bowen-ratio forced closure method. Compared to the corresponding ET_L, half-hourly daytime ET_EC was underestimated by 21.8% without the adjustment and 4.8% with the adjustment. Furthermore, nighttime ET_EC was adjusted using filtering/interpolation method. Mean error between half-hourly nighttime ET_EC and ET_L decreased from 30.2% without the adjustment to 10.3% with the adjustment. After such adjustment of day and night measurements, daily ET_EC was underestimated by 6.2% compared to ET_L. These results indicated that the adjusted ET_EC well matched with the ET_L. Moreover, the discrepancy of adjusted total ET_EC and ET_L was decreased to 3.2% after subtracting the overestimated ET by lysimeter resulting from irrigation and heavy rainfall events. Thus, after appropriate adjustments of observations, eddy covariance method is accurate in estimating maize ET in the arid region of northwest China.     

Research and field monitoring on transgenic crops by the Centro Internacional de Mejoramiento de Maíz y Trigo (CIMMYT)

The International Maize and Wheat Improvement Center (CIMMYT) aims to genetically enhance both crops and generate public sector-provided products for the resource poor, e.g., drought tolerant wheat and insect resistant maize, and through international–national partnerships facilitate the acquisition of improved germplasm for non-mandate crops in the cropping systems where maize and wheat thrives; e.g., GM-papaya through a national food security undertaking in Bangladesh. The Center also engages in public awareness campaigns in projects such as Insect Resistance Maize for Africa (IRMA), which includes food, feed and environmental safety, monitoring of resistance and establishment of refugia, non-target effects and gene flow. Monitoring of genetic resources is a wide concern among the centers of the Consultative Group on International Agricultural Research (CGIAR), with an emphasis on the quality of gene banks. Decisions, policies and procedures about monitoring should be science-based, and this requires education, an area where CIMMYT and other CGIAR centers can play an important role. There will be a need to continue to evaluate the need for, and type of monitoring, as new (and unique) products are developed and released in the emergent economies of the world.     

Urease activity and its relation to soil organic matter, microbial biomass nitrogen and urea-nitrogen assimilation by maize in a Brazilian Oxisol under no-tillage and tillage systems

 We studied the relationship between urease activity (UA) and soil organic matter (SOM), microbial biomass N (N_biom) content, and urea-N fertilizer assimilation by maize in a Dark Red Latosol (Typic Haplustox) cultivated for 9 years under no-tillage (NT), tillage with a disc plough (DP), and tillage with a moldboard plough (MP). Two soil depths were sampled (0–7.5 cm and 7.5–15 cm) at 4 different times during the crop cycle. Urea was applied at four different rates, ranging from 0 to 240 kg N ha^–1. The levels of fertilizer N did not affect the UA, SOM content, and N_biom content. No significant difference between the treatments (NT, DP, and MP) was observed for SOM during the experiment, probably because the major part of the SOM was in recalcitrant pools, since the area was previously cultivated (conventional tillage) for 20 years. The N_biom content explained 97% and 69% of the variation in UA in the upper and deeper soil layer, respectively. UA and biomass N were significantly higher in the NT system compared to the DP and MP systems. The highest maize productivity and urea-N recovery was also observed for the NT system. We observed that the increase in urea-N losses under NT, possibly as a consequence of a higher UA, was compensated for by the increase in N immobilized in the biomass. Received: 2 July 1999     

利用外源种质选育优良玉米自交系及强优势杂交种的实践与思考

以外引杂交种 785 99为基础材料分离获得优良玉米自交系齐 319。以齐 319为亲本与不同类群测验系杂交 ,所配组合均表现较强的杂种优势 ,特别是具有突出的抗锈病能力。其中鲁单 5 0即鲁原 92×齐 319优势最强。 1995～ 1997年在山东省区域试验和生产试验中产量居首位 ,并表现抗病、抗倒能力强 ,是目前生产上多抗性最好的优良品种之一 ,1999年山东省推广面积达 6 9 7× 10 4 hm2 。     

国审玉米郑单14播期、密度与高产机理研究

对郑单14的密度、播期及生理特点等一系列研究表明,郑单14的最适播种密度为52 500～60 000株/hm2;理想播期为5月25日至6月5日,不宜在6月10日以后播种.其表现高产稳产的主要生理原因是①叶面积指数变化合理,叶片持绿时间长,衰老慢,叶绿体中的光合色素、蛋白质和可溶性糖含量高;②过氧化物酶活性高,丙二醛积累少,光合效率高;③子粒体积大,灌浆时间长,千粒重高.     

魔芋与玉米间作群体中魔芋植株生长及葡苷聚糖含量变化的研究

设置玉米与魔芋1∶4、2∶4行比种植和净作魔芋3种不同的栽培模式,魔芋采用8.78、12.07、15.36和18.66万/hm24种种植密度,研究不同间作模式和种植密度对魔芋主要生长性状和产量品质的影响.结果表明,玉米遮荫有利魔芋生长,表现为植株交高,生长繁茂,发病轻,叶绿素和葡苷聚糖含量套作都较净作高.综合考虑,魔芋与玉米间作,以玉米∶魔芋=2∶4的间作模式、种植密度为15.36万株/hm2最好.