Much Improved Irrigation Use Efficiency in an Intensive Wheat-Maize Double Cropping System in the North China Plain

Crop yield and water use efficiency （WUE） in a wheat-maize double cropping system are influenced by short and uneven rainfalls in the North China Plain （NCP）, A 2-year experiment was conducted to investigate the effects of irrigation on soil water balance, crop yield and WUE to improve irrigation use efficiency in the cropping system, Soil water depletion （~SWS） by crop generally decreased with the increase of irrigation and rainfall, while ASWS for the whole rotation was relatively stable among these irrigation treatments, High irrigations in wheat season increased initial soil moisture and ASWS for subsequent maize especially in the drought season, Initial soil water influenced mainly by the irrigation and rainfall in the previous crop season, is essential to high yield in such cropping systems, Grain yield decreased prior to evapotranspiraUon （ET） when ET reached about 300mm for wheat, while maize showed various WUEs with similar seasonal ET, For whole rotation, WUE declined when ET exceeded about 650 mm, These results indicate great potential for improving irrigation use efficiency in such wheat-maize cropping system in the NCP, Based on the present results, reasonable irrigation schedules according to different annual rainfall conditions are presented for such a cropping system.

Using RAPD in Neisseria gonorrhoeae genotyping and transmission detection

The aim of this paper is to develop an applic-able Random Amplified Polymorphic DNAs(RAPD)method for genotyping Neisseria gonorrhoeae strain,and discuss the possibility of using the RAPD method to trace N.gonorrhoeae strain transmission route.Four different pretreatment methods were used on the N.gonorrhoeae genomic DNA component,and the best adaptive extract method was selected for RAPD.Different RAPD primers sequence was used for amplification and their differenti-ating capabilities for N.gonorrhoeae strains were com-pared.Applicable RAPD primer was selected for N.gonorrhoeae genotyping and then applied into transmis-sion detection.The results show that the so called cetyl-trimethylammonium bromide(CTAB)method for extracting genomic DNA could give integrated genomic DNA and give out relatively better RAPD fingerprint maps,subsequently,using selected RAPD primer could give out a group of amplification polymerase chain reac-tion bands.The fingerprint maps from different N.gonor-rhoeae strains were distinctive.Some main segments were common to all the N.gonorrhoeae strains tested.Some segments were different among the N.gonorrhoeae strains.According to the fingerprint maps and similarity index of different N.gonorrhoeae isolates,isolates from a pair of sex-partners were very similar.Based on these findings,the best extracting method and suitable RAPD primer were chosen.The RAPD fingerprint maps could type N.gonorrhoeae effectively and could be used as an additional approach in molecular epidemiology for tracing infection sources.