小麦全蚀病 (Take-all) 是一种具有毁灭性的土传病害，培育抗病材料是控制该病害的重要途径之一。华山新麦草 (Psathyrostachys huashanica Keng) 是小麦品种改良的重要遗传资源，特别是小麦全蚀病稀缺的抗性资源。在本研究中，相比感病亲本7182，小麦-华山新麦草渗入系H148的全蚀病抗性得到了显著性提升。为了明确H148抗病性的遗传机制，我们构建了H148和西农585的F₂遗传分离群体，且利用植物数量遗传体系“主基因+多基因”混合遗传模型分离分析法对其研究发现，H148的全蚀病抗性受到两对主效基因的共同控制，这两对主效基因存在一定的加性、显性和上位性效应。同时，结合集群分离分析法 (Bulked Segregant Analysis, BSA) 和小麦660K基因芯片筛选出与抗病相关的外源特异性SNP，主要分布于小麦2A染色体。根据特异性SNP开发竞争性等位基因特异性PCR (Kompetitive allele specific PCR, KASP) 分子标记，对F₂群体进行基因分型，最终在2A染色体的68.8-70.1Mb区间内定位到一个主效的QTL。该目标区间在小麦参考基因组序列上存在62个候选基因，经基因功能注释显示，两个可编码蛋白的基因与系统性提升植物根系抗性相关，被预测可能参与了小麦对全蚀病的抗病反应。总之，小麦-华山新麦草渗入系H148的选育以及抗病QTL的定位，以期为小麦抗全蚀病分子辅助育种和抗病基因的精细定位提供一定的参考信息。

Chlorination is usually an economical method for treating clogging in drip emitters during sewage application. Appropriate assessment of the responses of soil and crop is essential for determining an optimal chlorination scheme. During 2008 to 2009, field experiments were conducted in a solar-heated greenhouse for tomato drip irrigated with secondary sewage effluent, to investigate the influences of chlorine injection intervals and levels on soil chemical properties and nitrogen uptake. Injection intervals ranging from two to eight weeks and injection concentrations ranging from 2 to 50 mg L-1 were used. A salinity factor and a nutrient factor were extracted from the pool of the nine soil chemical constituents using factor analysis method. The results demonstrated that chlorination practices increased the residual Cl in the soil, resulting in an increased salinity factor, especially for the frequent chlorination at a high injection concentration. Chlorination weakened the accumulation of nutrients factor in the upper soil layer. Nitrogen uptake of the tomato plants also was inhibited by the increased salinity in the upper soil layer caused by high chlorination levels. In order to reduce the unfavorable effect on soil chemical properties and nitrogen uptake, chlorination scheme with concentrations of lower than 20 mg L-1 was recommended.

To determine the genetic diversity and population structure of sweet potato accessions cultivated in China, and to establish the genetic relationships among their germplasm types, a representative collection of 240 accessions was analyzed using inter-simple sequence repeat (ISSR) markers. The mean genetic similarity coefficient, Nei’s gene diversity, and shared allele distance of tested sweet potato accessions were 0.7302, 0.3167 and 0.2698, respectively. The 240 accessions could be divided into six subgroups and five subpopulations based on neighbor-joining (NJ) clustering and STRUCTURE results, and obvious genetic relationships among the tested sweet potato accessions were identified. The marker-based NJ clustering and population structure showed no distinct assignment pattern corresponding to flesh color or geographical ecotype of the tested sweet potato germplasm. Analysis of molecular variance (AMOVA) revealed small but significant difference between white and orange-fleshed sweet potato accessions. Small but significant difference were also observed among sweet potato accessions from the Southern summer-autumn sweet potato region, the Yellow River Basin spring and summer sweet potato region and the Yangtze River Basin summer sweet potato region. This study demonstrates that genetic diversity in the tested sweet potato germplasm collection in China is lower than that in some reported sweet potato germplasm collections from other regions. Pedigree investigations suggest that more diverse Chinese sweet potato varieties should be formed by broadening the selection scope of breeding parents and incorporating the introduced varieties into future breeding programs.

Chlorination has been recognized as an efficient and economically favorable method for treating clogging in drip emitters caused by biological growth during sewage application. Further important criteria for determining an optimal chlorination scheme are the different responses of crops to the chloride added into the soil through chlorination. During two seasons in 2008 and 2009, field experiments were conducted in a solar-heated greenhouse with drip irrigation systems applying secondary sewage effluent to tomato plants to investigate the influences of chlorine injection intervals and levels on plant growth, yield, fruit quality, and emitter clogging. Injection intervals ranging from 2 to 8 wk and injection concentrations ranging 2-50 mg L-1 of free chlorine residual at the end of the laterals were used. For the 2008 experiments, the yield from the treatments of sewage application with chlorination was 7.5% lower than the yield from the treatment of sewage application without chlorination, while the yields for the treatments with and without chlorination were similar for the 2009 experiments. The statistical tests indicated that neither the chlorine injection intervals and concentrations nor the interactions between the two significantly influenced plant height, leaf area, or tomato yield for both years. The qualities of the fruit in response to chlorination were parameter-dependent. Chlorination did not significantly influence the quality of ascorbic acid, soluble sugar, or soluble acids, but the interaction between the chlorine injection interval and the chlorine concentration significantly influenced the levels of soluble solids. It was also confirmed that chlorination was an effective method for reducing biological clogging. These results suggested that chlorination is safe for a crop that has a moderate sensitivity to chlorine, like tomato, and can maintain a high level of performance in drip irrigation systems applying sewage effluent