Abstract
BackgroundContinuous storage root formation and bulking (CSRFAB) in sweetpotato is an important trait from agronomic and biological perspectives. Information about the molecular mechanisms underlying CSRFAB traits is lacking.ResultsHere, as a first step toward understanding the genetic basis of CSRFAB in sweetpotato, we performed a genome-wide association study (GWAS) using phenotypic data from four distinct developmental stages and 33,068 single nucleotide polymorphism (SNP) and insertion-deletion (indel) markers. Based on Bonferroni threshold (p-value < 5 × 10− 7), we identified 34 unique SNPs that were significantly associated with the complex trait of CSRFAB at 150 days after planting (DAP) and seven unique SNPs associated with discontinuous storage root formation and bulking (DCSRFAB) at 90 DAP. Importantly, most of the loci associated with these identified SNPs were located within genomic regions (using Ipomoea trifida reference genome) previously reported for quantitative trait loci (QTL) controlling similar traits. Based on these trait-associated SNPs, 12 and seven candidate genes were respectively annotated for CSRFAB and DCSRFAB traits. Congruent with the contrasting and inverse relationship between discontinuous and continuous storage root formation and bulking, a DCSRFAB-associated candidate gene regulates redox signaling, involved in auxin-mediated lateral root formation, while CSRFAB is enriched for genes controlling growth and senescence.ConclusionCandidate genes identified in this study have potential roles in cell wall remodeling, plant growth, senescence, stress, root development and redox signaling. These findings provide valuable insights into understanding the functional networks to develop strategies for sweetpotato yield improvement. The markers as well as candidate genes identified in this pioneering research for CSRFAB provide important genomic resources for sweetpotato and other root crops.
Highlights
Continuous storage root formation and bulking (CSRFAB) in sweetpotato is an important trait from agronomic and biological perspectives
Perenniality in sweetpotato is associated with CSRFAB [3] due to its capacity to keep vegetative growth overtime that leads to increased photosynthetic activity and continuous dry matter partitioning into the storage root organ [4]
We observed positive correlations between area under growth progress curve (AUGPC) and yield component traits at each harvest time, with the highest positive correlation coefficient recorded at 150 days after planting (DAP) (0.91)
Summary
Continuous storage root formation and bulking (CSRFAB) in sweetpotato is an important trait from agronomic and biological perspectives. Subsistence agricultural systems use piecemeal/multiple harvesting strategies to increase profitability by ensuring availability of their product over a longer growing season due to continuous storage root formation and bulking (CSRFAB). CSRFAB genotypes primarily invest in vegetative growth and later change to a reproduction phase by enhanced carbon partitioning to storage root development while continuing vegetative growth [5, 4]. This drastically increases productivity due to increased photosynthesizing green materials in CSRFAB genotypes compared to DCSRFAB genotypes [6]. Sweetpotato cultivars are capable of delaying senescence and maintaining carbon assimilation due to persistent photosynthetic activity over longer periods [7]
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