Identification of putative QTLs for seedling stage phosphorus starvation response in finger millet ( Eleusine coracana L. Gaertn.) by association mapping and cross species synteny analysis

Abstract

A germplasm assembly of 128 finger millet genotypes from 18 countries was evaluated for seedling-stage phosphorus (P) responses by growing them in P sufficient (P _suf ) and P deficient (P _def ) treatments. Majority of the genotypes showed adaptive responses to low P condition. Based on phenotype behaviour using the best linear unbiased predictors for each trait, genotypes were classified into, P responsive, low P tolerant and P non-responsive types. Based on the overall phenotype performance under P _def , 10 genotypes were identified as low P tolerants. The low P tolerant genotypes were characterised by increased shoot and root length and increased root hair induction with longer root hairs under P _def , than under P _suf . Association mapping of P response traits using mixed linear models revealed four quantitative trait loci (QTLs). Two QTLs ( qLRDW. 1 and qLRDW. 2) for low P response affecting root dry weight explained over 10% phenotypic variation. In silico synteny analysis across grass genomes for these QTLs identified putative candidate genes such as Ser-Thr kinase and transcription factors such as WRKY and basic helix-loop-helix ( bHLH). The QTLs for response under P _suf were mapped for traits such as shoot dry weight ( qHSDW. 1) and root length ( qHRL. 1). Putative associations of these QTLs over the syntenous regions on the grass genomes revealed proximity to cytochrome P450, phosphate transporter and pectin methylesterase inhibitor ( PMEI) genes. This is the first report of the extent of phenotypic variability for P response in finger millet genotypes during seedling-stage, along with the QTLs and putative candidate genes associated with P starvation tolerance.