Rama Reddy Nagaraja Reddy, Ragimasalawada Madhusudhana, Sabbavarapu Murali Mohan, Nadoor Seetharama, Patil Jagannatha Vishnu
Marker-assisted selection Lab, ICAR-Directorate of Sorghum Research (DSR), Rajendranagar, Hyderabad 500 030, India.
BMC Genomics. 2014 Oct 18;15(1):909. doi: 10.1186/1471-2164-15-909.
Sorghum [Sorghum bicolor (L.) Moench] is an important dry-land cereal of the world providing food, fodder, feed and fuel. Stay-green (delayed-leaf senescence) is a key attribute in sorghum determining its adaptation to terminal drought stress. The objective of this study was to validate sorghum stay-green quantitative trait loci (QTL) identified in the past, and to identify new QTL in the genetic background of a post-rainy adapted genotype M35-1.
A genetic linkage map based on 245 F9 Recombinant Inbred Lines (RILs) derived from a cross between M35-1 (more senescent) and B35 (less senescent) with 237 markers consisting of 174 genomic, 60 genic and 3 morphological markers was used. The phenotypic data collected for three consecutive post-rainy crop seasons on the RIL population (M35-1 × B35) was used for QTL analysis. Sixty-one QTL were identified for various measures of stay-green trait and each trait was controlled by one to ten QTL. The phenotypic variation explained by each QTL ranged from 3.8 to 18.7%. Co-localization of QTL for more than five traits was observed on two linkage groups i.e. on SBI-09-3 flanked by S18 and Xgap206 markers and, on SBI-03 flanked by XnhsbSFCILP67 and Xtxp31. QTL identified in this study were stable across environments and corresponded to sorghum stay-green and grain yield QTL reported previously. Of the 60 genic SSRs mapped, 14 were closely linked with QTL for ten traits. A genic marker, XnhsbSFCILP67 (Sb03g028240) encoding Indole-3-acetic acid-amido synthetase GH3.5, was co-located with QTL for GLB, GLM, PGLM and GLAM on SBI-03. Genes underlying key enzymes of chlorophyll metabolism were also found in the stay-green QTL regions.
We validated important stay-green QTL reported in the past in sorghum and detected new QTL influencing the stay-green related traits consistently. Stg2, Stg3 and StgB were prominent in their expression. Collectively, the QTL/markers identified are likely candidates for subsequent verification for their involvement in stay-green phenotype using NILs and to develop drought tolerant sorghum varieties through marker-assisted breeding for terminal drought tolerance in sorghum.
高粱[Sorghum bicolor (L.) Moench]是世界上一种重要的旱地谷物，可提供食物、饲料、饲草和燃料。持绿性（叶片衰老延迟）是高粱决定其对终末期干旱胁迫适应性的关键特性。本研究的目的是验证过去鉴定出的高粱持绿数量性状位点（QTL），并在适应雨后环境的基因型M35-1的遗传背景中鉴定新的QTL。
使用了一个基于245个F9重组自交系（RIL）构建的遗传连锁图谱，这些RIL系来自M35-1（衰老程度较高）和B35（衰老程度较低）的杂交后代，图谱包含237个标记，其中有174个基因组标记、60个基因标记和3个形态学标记。对RIL群体（M35-1×B35）连续三个雨后作物季节收集的表型数据用于QTL分析。针对持绿性状的各种指标鉴定出61个QTL，每个性状由1至10个QTL控制。每个QTL解释的表型变异范围为3.8%至18.7%。在两个连锁群上观察到超过五个性状的QTL共定位，即位于S18和Xgap206标记两侧的SBI-09-3上，以及位于XnhsbSFCILP67和Xtxp31两侧的SBI-03上。本研究中鉴定出的QTL在不同环境下稳定，并且与先前报道的高粱持绿和籽粒产量QTL相对应。在定位的60个基因SSR中，有14个与十个性状的QTL紧密连锁。一个编码吲哚-3-乙酸酰胺合成酶GH3.5的基因标记XnhsbSFCILP67（Sb03g028240）与SBI-03上的GLB、GLM、PGLM和GLAM的QTL共定位。在持绿QTL区域还发现了叶绿素代谢关键酶的相关基因。
我们验证了过去报道的高粱中重要的持绿QTL，并一致检测到影响持绿相关性状的新QTL。Stg2、Stg3和StgB在表达上较为突出。总体而言，鉴定出的QTL/标记可能是后续使用近等基因系验证其参与持绿表型的候选对象，并通过标记辅助育种培育耐旱高粱品种，以实现高粱对终末期干旱的耐受性。
