摘要：The partial 16 S r RNA gene sequences（100 to 500 bp） were widely used to reveal rumen bacterial composition influenced by diets, while quantification of the changed uncultured bacteria was inconvenient due to difficult designing of specific primers based on short sequences. This study evaluated the effect of forage resources on rumen bacterial diversity and developed new strategy for primer design based on short sequences to quantify the changed uncultured bacteria. Denaturing gradient gel electrophoresis（DGGE） analysis and subsequent band sequencing were used to reveal the distinct rumen bacteria composition in cows fed with two forage sources（single corn stover vs. mixed forages including alfalfa hay and corn silage）. The bacterial diversity in the rumen of dairy cows fed with corn stover was lower than that with mixed forages（P0.05）. The bacterium named R-UB affiliating to uncultured Succinivibrionaceae was identified, and it was abundant in the rumen of cows fed with mixed forages compared to corn stover. The full length 16 S r RNA gene sequences with identity of 97% to the R-UB 16 S r RNA gene sequence were obtained from Gen Bank and used to design specific primers to quantify uncultured bacterium R-UB. All sequences of amplicon from the new primers were of 100% identity to R-UB sequences indicating the high specificity of new primers. Quantitative PCR confirmed that abundance of R-UB in the rumen of cows fed with corn stover was lower than those fed with mixed forages（P0.01）. New strategy for designing primers based on partial 16 S r RNA genes to quantify targeted uncultured bacteria was successfully developed. The rumen bacteria descending significantly in the cows fed corn stover compared to those fed mixed forages was identified as uncultured R-UB from Succinivibrionaceae.

摘要：Dear Editor,Gynoecism has been extensively exploited in cucumber breeding. The utilization of a gynoecious line permits earlier pro- duction of hybrids, higher yield, and more concentrated fruit set. In addition, the utilization of a gynoecious line eliminates the need for hand emasculation and reduces the labor cost of crossing （Robinson, 2000）. Therefore, the development of gynoeoious inbred lines is instrumental for cucumber breeding. Gynoecious inbreds can be produced by selection from crosses of monoecious inbreds, or can arise spontaneously from natural variation. However, both methods have disadvantages. For instance, the time-consuming and laborious process of crossing can also lead to the introduction of undesirable traits,

摘要：【目的】秸秆还田作为一种有效的培肥方式,对土壤固碳效果显著,但对于深层土壤有机碳的影响还存在不确定性。分析不同秸秆还田方式下褐土剖面土壤有机碳(SOC)储量变化,为褐土区秸秆还田措施优化和固碳减排等提供科学依据。【方法】长期秸秆还田试验开始于1992年,采用裂区设计,主区为化肥春季和秋季施用,副区为4个秸秆还田处理:秸秆不还田(CK)、秸秆覆盖还田(SM)、秸秆粉碎后直接还田(SC)和秸秆过腹还田(CM)。在2013年春玉米收获后采集0—100 cm土层土壤样品,分析不同秸秆还田方式下SOC和土壤养分含量。【结果】在春季和秋季施肥下,与CK相比,CM、SM和SC处理表层(0—20 cm)SOC含量显著提高,而SM和SC处理40—60和80—100 cm SOC含量显著降低。同时,与CK处理相比各处理SOC储量变化量在处理间存在显著差异。在春季和秋季施肥下,与CK相比,SM、SC和CM处理表层SOC储量平均分别增加2.32、5.42和12.60 t/hm^(2),且CM处理显著高于SM和SC处理;而在底层(40—100 cm)平均分别降低3.98、6.99和3.76 t/hm^(2);0—100 cm,CM处理SOC储量增加9.62 t/hm^(2),而SM和SC处理平均分别降低1.81和5.36 t/hm^(2)。冗余分析结果表明,有机碳输入和土壤养分对表层碳储量变化的总解释率为90.10%,而对下层(20—100 cm)的总解释率仅为31.80%。其中,影响表层碳储量变化的主要因子是有效磷(解释率为80.10%),而下层则是全氮(25.28%)。【结论】在施用化肥基础上,长期秸秆还田促进表层碳累积,但底层氮素供应不足引起碳耗竭。总体上,秸秆过腹还田是褐土区农田培肥和增产的最优秸秆还田方式。