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 (Psuf) and P deficient (Pdef) 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 Pdef, 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 Pdef, than under Psuf. 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 Psuf 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.
Highlights
The major plant nutrient, Phosphorus (P) has a plentiful distribution in the soil, but is the most limiting nutrient, because of predominant P fixation [1,2,3], reaching up to 80% as organic P [4]
All the genotypes germinated within 4–5 days of sowing in the perlite filled plastic pots both under P deficient (Pdef) and P sufficient (Psuf) treatments
After 30 days of germination, under Pdef, average shoot length (SL) and RHD increased while root length (RL) decreased than under Psuf
Summary
The major plant nutrient, Phosphorus (P) has a plentiful distribution in the soil, but is the most limiting nutrient, because of predominant P fixation [1,2,3], reaching up to 80% as organic P [4]. To sustain agriculture under P scarce systems, it is imperative that P application should be reduced in the future This may help in reducing P fertilizer requirement of crops, while helping to prevent environmental degradation [9] due to excess applied P, as well as in reducing anti-nutritional factors such as Phytate accumulation in grains that reduces the bioavailability of mineral elements such as Ca2+, Mg2+, Zn2+, Fe2+, Cu2+ and Mn2+ [10]. This can be achieved by improving the genetic potential of crop varieties to grow under P minimal conditions [11, 12], as well as to reduce grain phytate content [13,14,15]
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