An Efficient Strategy Combining SSR Markers- and Advanced QTL-seq-driven QTL Mapping Unravels Candidate Genes Regulating Grain Weight in Rice.
Development and use of genome-wide informative simple sequence repeat (SSR) markers and novel integrated genomic strategies are vital to drive genomics-assisted breeding applications and for efficient dissection of quantitative trait loci (QTLs) underlying complex traits in rice. The present study developed 6244 genome-wide informative SSR markers exhibitingin silicofragment length polymorphism based on repeat-unit variations among genomic sequences of 11indica, japonica, aus, and wild rice accessions. These markers were mapped on diverse coding and non-coding sequence components of known cloned/candidate genes annotated from 12 chromosomes and revealed a much higher amplification (97%) and polymorphic potential (88%) along with wider genetic/functional diversity level (16-74% with a mean 53%) especially among accessions belonging toindicacultivar group, suggesting their utility in large-scale genomics-assisted breeding applications in rice. A high-density 3791 SSR markers-anchored genetic linkage map (IR 64 × Sonasal) spanning 2060 cM total map-length with an average inter-marker distance of 0.54 cM was generated. This reference genetic map identified six major genomic regions harboring robust QTLs (31% combined phenotypic variation explained with a 5.7-8.7 LOD) governing grain weight on six rice chromosomes. One strong grain weight major QTL region (OsqGW5.1) was narrowed-down by integrating traditional QTL mapping with high-resolution QTL region-specific integrated SSR and single nucleotide polymorphism markers-based QTL-seq analysis and differential expression profiling. This led us to delineate two natural allelic variants in two knowncis-regulatory elements (RAV1AAT and CARGCW8GAT) of glycosyl hydrolase and serine carboxypeptidase genes exhibiting pronounced seed-specific differential regulation in low (Sonasal) and high (IR 64) grain weight mapping parental accessions. Our genome-wide SSR marker resource (polymorphic within/between diverse cultivar groups) and integrated genomic strategy can efficiently scan functionally relevant potential molecular tags (markers, candidate genes and alleles) regulating complex agronomic traits (grain weight) and expedite marker-assisted genetic enhancement in rice.
National Institute of Plant Genome Research (NIPGR) New Delhi, India.
Anurag
A
Daware
National Institute of Plant Genome Research (NIPGR) New Delhi, India.
Sweta
S
Das
National Institute of Plant Genome Research (NIPGR) New Delhi, India.
Rishi
R
Srivastava
National Institute of Plant Genome Research (NIPGR) New Delhi, India.
Saurabh
S
Badoni
Rice Section, Division of Genetics, Indian Agricultural Research Institute (IARI) New Delhi, India.
Ashok K
AK
Singh
National Institute of Plant Genome Research (NIPGR) New Delhi, India.
Pinky
P
Agarwal
National Institute of Plant Genome Research (NIPGR) New Delhi, India.
Swarup K
SK
Parida
National Institute of Plant Genome Research (NIPGR) New Delhi, India.
Akhilesh K
AK
Tyagi
QTL; QTL-seq; SNP; SSR; grain weight; rice