本研究的目的是利用我们在先前研究中构建的F₁杂交群体的高密度遗传连锁图谱定位与春季再生相关的数量性状位点（quantitative trait loci, QTL）。该群体包含392个子代，且亲本在春季再生性状上表现出明显的差异。在两个地点连续统计了两年的表型数据，并利用IciMapping软件进行QTL定位分析。利用单个环境中表型的平均值和最佳线性无偏预测（Best Linear Unbiased Prediction，BLUP）作为QTL定位的表型，总共鉴定到36个与春季再生性状显著关联的加性QTL。其中，有十个QTL分别解释了超过10％的表型变异（phenotypic variation, PVE），在P1亲本（父本）中有四个，P2亲本（母本）中有六个。在这些加性QTL中共有六个重叠的QTL区间，在P1和P2中分别有两个和四个。在P1中，两个重叠的区间都位于连锁群7D上。在P2中，PVE >10％的四个QTL在连锁群6D上定位到相同区间。此外，在P2中鉴定出六对显著的上位性QTL，而在P1中没有定位到上位性QTL。在四个重叠的QTL（qCP2019-8，qLF2019-5，qLF2020-4和qBLUP-3）所处区间内筛选到一个候选基因，该基因被注释为MAIL1，拟南芥中的同源基因在植株的生长中起重要作用。本研究定位到的QTLs是利用标记辅助选择对紫花苜蓿春季再生性状进行遗传改良的宝贵资源，鉴定的相关基因为深入了解紫花苜蓿春季再生的遗传特性提供依据。

Alfalfa (Medicago sativa L.) is an important forage crop and is also a target of many fungal diseases including Fusarium spp.  As of today, very little information is available about molecular mechanisms that contribute to pathogenesis and defense responses in alfalfa against Fusarium spp. and specifically against Fusarium proliferatum, the causal agent of alfalfa root rot.  In this study, we used a proteomic approach to identify inducible proteins in alfalfa during a compatible interaction with F. proliferatum strain YQC-L1.  Samples used for the two-dimensional gel electrophoresis (2-DE) and MALDI-TOF/TOF mass spectrometry were from roots and leaves of alfalfa cultivar AmeriGraze 401+Z and WL656HQ.  Plants were grown in hydroponic conditions and at 4 days post inoculation with YQC-L1.  Our disease symptom assays indicated that AmeriGraze 401+Z  was tolerant to YQC-L1 infection while WL656HQ was highly susceptible.  Analysis of differentially expressed proteins found in the 2-DE was further characterized using the MASCOT MS/MS ion search software and associated databases to identify multiple proteins that might be involved in F. proliferatum resistance.  A total of 66 and 27 differentially expressed proteins were found in the roots and leaves of the plants inoculated with YQC-L1, respectively.  These identified proteins were placed in various categories including defense and stress response related metabolism, photosynthesis and protein synthesis.  Thirteen identified proteins were validated for their expressions by quantitative reverse transcription (qRT)-PCR.  Our results suggested that some of the identified proteins might play important roles in alfalfa resistance against Fusarium spp.  These finding could facilitate further dissections of molecular mechanisms controlling root rot disease in alfalfa and potentially other legume crops.   

Cultivar selection is important for alfalfa (Medicago sativa L.) hay production. From 2009 to 2012, a field study was conducted to evaluate the dry matter yield (DMY) of 28 cultivars in Cangzhou District of Hebei province, China, and to determine the most suitable cultivars for this province and other zones with similar climate conditions. 28 alfalfa cultivars were sown in late March of 2009 and were harvested for hay four times in each subsequent year. The results showed that the climatic conditions resulted in significant differences in annual DMY among years, with the second year being the highest and the first year the lowest. The top five cultivars with the highest total DMY were L2750 (62.75 t ha-1), Horn (62.72 t ha-1), 86-266 (61.55 t ha-1), German (61.44 t ha-1) and Zhongmu 1 (61.18 t ha-1), respectively. Across all four years, first harvest had the highest ratios to annual DMY except the cultivar of Rambler, while the fourth harvest had the lowest ratio. There were positive correlation relationships between DMY of each harvest and annual DMY, and the correlation coefficients were all significant in four years. And the path coefficients of first harvest were always the highest in four years. The qualities showed small variations among these cultivars and the cultivar L3750 presented the highest crude protein in both years. Crude protein had significant positive correlation with relative feed value (RFV) in both years while crude fiber had significant negative correlation with RFV and crude fiber.