A low malic acid trait in cranberry fruit: genetics, molecular mapping, and interaction with a citric acid locus

Stephanie Kay Fong, Joseph Kawash, Yifei Wang, Jennifer Johnson-Cicalese, James Polashock, Nicholi Vorsa

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1 Scopus citations

Abstract

The fruit of commercial cranberry (Vaccinium macrocarpon Ait.) cultivars have relatively high concentrations of malic acid (MA) and citric acid (CA), and, to a lesser extent, quinic acid. These acids contribute to the high titratable acidity (TA), a measure of tartness, of cranberry fruit, which typically ranges from 2.3 to 2.5% citric acid equivalents in commercial cultivars. Thus, considerable amounts of sugar are added (“added sugar”) in products such as sweetened-dried cranberries and juices. Within our cranberry germplasm collection, a unique accession was identified with fruit having a TA ≈ 1.5%, where MA concentration was reduced to ~ 4 mg/g fresh weight (FW), compared to ~ 8 mg/g FW in current cultivars. Inbred crosses derived from this accession yielded progeny with a lower MA phenotype (~ 2 mg/g FW). Observed segregation indicated the accession was heterozygous (Mala/mala) for a low MA allele (mala) and very low MA progeny were homozygous (mala/mala). MA was reduced approximately 75% in these populations relative to standard cultivars. The homozygous mala/mala locus also depressed fruit CA and quinic acid concentrations. Quantitative trait loci mapping identified a region on chromosome 4 associated with low MA. The combined segregation of three half-sib populations derived from the low MA accession generated effective (within < 1 cM) Kompetitive allele-specific PCR (KASP) markers for use in breeding of cranberry cultivars with lower MA. Dihybrid populations were developed having a previously described low CA allele, cita, with the mala alleles of this study to explore the interaction of alleles at both loci.

Original languageEnglish (US)
Article number4
JournalTree Genetics and Genomes
Volume17
Issue number1
DOIs
StatePublished - Feb 2021

All Science Journal Classification (ASJC) codes

  • Forestry
  • Molecular Biology
  • Genetics
  • Horticulture

Keywords

  • Citric acid
  • Fruit titratable acidity
  • GBS
  • KASP
  • Malic acid
  • Marker-assisted selection
  • Quantitative trait loci
  • Quinic acid
  • SNP
  • Vaccinium

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