Flesh browning after cutting or bruising reduces the commercial value of apple fruit. Here, we investigated the genetic factors that regulate flesh browning (at 15 min and 24 h after grating) by a genome-wide association study (GWAS) of 24 sib-families (468 genotypes). Three quantitative trait loci (QTLs) were detected on chr5, chr16, and chr17. Their effects were estimated in a germplasm collection of 86 cultivars and selection lines: flesh browning differed with the genotypes of SNPs linked to these QTLs, respectively explaining 31.3%, 3.3%, and 23.7% of phenotypic variance at 15 min, and 36.7%, 11.0%, and 14.8% of variance at 24 h. Homozygous recessive alleles at these QTLs were associated with low browning. ‘Aori 27’, a rare cultivar that never browns even 5 days after grating, was homozygous recessive at all three QTLs. Browning was clearly lower in cultivars that were homozygous recessive at two QTLs, rather than one or none. We analyzed browning-related traits—polyphenol oxidase (PPO) activity, total polyphenol content, and juice browning—by GWAS using the germplasm collection. A QTL for PPO activity was detected on chr5, where PPO genes are located; and QTLs for total polyphenol content and juice browning were detected on chr16, where leucoanthocyanidin reductase gene is located. No QTLs for the browning-related traits were detected on chr17. These results indicate that the juice browning is mainly regulated by polyphenol content (chr16 QTL), whereas the flesh browning is also regulated by additional factors, including PPO activity (chr5 QTLs). These findings will facilitate development of non-browning apple cultivars.

切块或青紫后的果肉褐变会降低苹果果实的商业价值。在这里，我们通过对24个同胞家族（468个基因型）的全基因组关联研究（GWAS），研究了调节果肉褐变的遗传因素（在磨碎后15分钟和24小时）。在chr5，chr16和chr17上检测到三个定量性状基因座（QTL）。在86个品种和选择系的种质资源库中评估了它们的作用：果肉褐变与与这些QTL相关的SNP的基因型不同，分别解释了15分钟时表型变异的31.3％，3.3％和23.7％，以及36.7％， 11.0％，以及24小时方差的14.8％。这些QTL上的纯合隐性等位基因与低褐变相关。'Aori 27'是一种罕见的品种，即使在磨碎后5天也不会褐变，在所有三个QTL上都是纯隐性的。在两个QTL纯合隐性的品种中，褐变明显降低，而不是一个或一个。我们使用种质收集方法通过GWAS分析了褐变相关性状-多酚氧化酶（PPO）活性，总多酚含量和果汁褐变。在chr5上检测到了PPO活性的QTL，该基因位于Phr基因上。在白蛋白花青素还原酶基因所在的chr16上检测到了总多酚含量和果汁褐变的QTL。在chr17上未检测到褐变相关性状的QTL。这些结果表明，果汁褐变主要受多酚含量（chr16 QTL）的调节，而果肉褐变还受其他因素（包括PPO活性（chr5 QTL））的调节。这些发现将促进非褐苹果品种的发展。