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.

商业蔓越莓（越桔大果的果实Ait。）品种的苹果酸（MA）和柠檬酸（CA）含量相对较高，奎宁酸含量较低。这些酸有助于蔓越莓的高滴定度酸度（TA），这是酸度的量度，通常在商业品种中为2.3至2.5％的柠檬酸当量。因此，在诸如甜干小红莓和果汁等产品中添加了大量的糖（“添加的糖”）。在我们的蔓越莓种质资源库中，鉴定出独特的种质，其果实的TA≈1.5％，MA浓度降低至〜4 mg / g鲜重（FW），而当前品种为〜8 mg / g FW。从该种获得的近交杂交产生的后代具有较低的MA表型（〜2 mg / g FW）。观察到的分离表明该种是杂合的（低等位基因（mala）和非常低的MA后代的纯合子（mala / mala）为Mala / mala。与标准品种相比，这些人群中的MA降低了约75％。纯合的mala / mala基因座也降低了果实CA和奎宁酸的浓度。数量性状基因座作图鉴定了4号染色体上与低MA相关的区域。来自低MA的三个半同胞群体的组合分离产生了有效的（<1 cM以内）竞争性等位基因特异性PCR（KASP）标记，用于MA较低的蔓越莓品种的育种。Dihybrid群体开发了等位基因具有先前描述的低CA，CITA，与念珠 本研究的等位基因探讨了两个基因座上等位基因的相互作用。