Spring regrowth is an important trait for perennial plants including alfalfa, the most cultivated forage legume worldwide.  However, the genetic and genomic basis of the trait is largely unknown in alfalfa due to its complex genetic background of the tetroploid genome.  The objective of this study was to identify quantitative trait loci (QTLs) associated with spring regrowth using high-resolution genetic linkage maps we constructed previously.  In total, 36 significant additive effect QTLs for the trait were detected.  Among them, 10 QTLs individually explained more than 10% of the phenotypic variation (PVE) with four in P1 and six in P2.  Six overlapped QTLs intervals were detected with two and four intervals distributed in P1 and P2, respectively.  In P1, both overlapped genomic regions were located on homolog 7D.  In P2, the four QTLs with PVE>10% were co-localized on homolog 6D.  Meanwhile, six pairs of significant epistatic QTLs were identified in P2.  Screening of potential candidate genes associated with four overlapped QTLs (qCP2019-8, qLF2019-5, qLF2020-4, and qBLUP-3) narrowed down one candidate annotated as MAIL1.  The Arabidopsis homolog gene has been reported to play an important role in plant growth.  Therefore, the detected QTLs are valuable resources for genetic improvement of alfalfa spring vigor using marker-assisted selection (MAS), and further identification of the associated genes would provide insights into genetic control of spring regrowth in alfalfa.

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.