Zhang Tiejun, Yu Long-Xi, Zheng Ping, Li Yajun, Rivera Martha, Main Dorrie, Greene Stephanie L
Plant and Germplasm Introduction and Testing Research, United States Department of Agriculture-Agricultural Research Service, Prosser, Washington, United States of America.
Department of Horticulture, Washington State University, Pullman, Washington, United States of America.
PLoS One. 2015 Sep 25;10(9):e0138931. doi: 10.1371/journal.pone.0138931. eCollection 2015.
Drought resistance is an important breeding target for enhancing alfalfa productivity in arid and semi-arid regions. Identification of genes involved in drought tolerance will facilitate breeding for improving drought resistance and water use efficiency in alfalfa. Our objective was to use a diversity panel of alfalfa accessions comprised of 198 cultivars and landraces to identify genes involved in drought tolerance. The panel was selected from the USDA-ARS National Plant Germplasm System alfalfa collection and genotyped using genotyping by sequencing. A greenhouse procedure was used for phenotyping two important traits associated with drought tolerance: drought resistance index (DRI) and relative leaf water content (RWC). Marker-trait association identified nineteen and fifteen loci associated with DRI and RWC, respectively. Alignments of target sequences flanking to the resistance loci against the reference genome of M. truncatula revealed multiple chromosomal locations. Markers associated with DRI are located on all chromosomes while markers associated with RWC are located on chromosomes 1, 2, 3, 4, 5, 6 and 7. Co-localizations of significant markers between DRI and RWC were found on chromosomes 3, 5 and 7. Most loci associated with DRI in this work overlap with the reported QTLs associated with biomass under drought in alfalfa. Additional significant markers were targeted to several contigs with unknown chromosomal locations. BLAST search using their flanking sequences revealed homology to several annotated genes with functions in stress tolerance. With further validation, these markers may be used for marker-assisted breeding new alfalfa varieties with drought resistance and enhanced water use efficiency.
抗旱性是提高干旱和半干旱地区苜蓿生产力的重要育种目标。鉴定参与耐旱性的基因将有助于苜蓿的育种，以提高其抗旱性和水分利用效率。我们的目标是利用一个由198个品种和地方品种组成的苜蓿种质多样性群体来鉴定参与耐旱性的基因。该群体选自美国农业部农业研究局国家植物种质系统的苜蓿种质库，并通过测序基因分型进行基因分型。采用温室试验方法对与耐旱性相关的两个重要性状进行表型分析：抗旱指数（DRI）和相对叶片含水量（RWC）。标记-性状关联分析分别鉴定出19个和15个与DRI和RWC相关的位点。将抗性位点侧翼的目标序列与蒺藜苜蓿参考基因组进行比对，发现了多个染色体位置。与DRI相关的标记位于所有染色体上，而与RWC相关的标记位于染色体1、2、3、4、5、6和7上。在染色体3、5和7上发现了DRI和RWC之间显著标记的共定位。本研究中与DRI相关的大多数位点与报道的苜蓿干旱条件下与生物量相关的QTL重叠。另外一些显著标记定位于几个染色体位置未知的重叠群。利用其侧翼序列进行BLAST搜索，发现与几个具有胁迫耐受功能的注释基因具有同源性。经过进一步验证，这些标记可用于标记辅助育种新的具有抗旱性和提高水分利用效率的苜蓿品种。
