Development and application of KASP molecular marker for accelerated breeding of low-acid Cerasus humilis cultivars

The KASP13 marker is located on chromosome 1 of Cerasus humilis. The AA genotype is associated with high acidity, whereas the AC genotype is associated with low acidity, with a prediction accuracy of 86.84%. This marker can be used to develop low-acid C. humilis cultivars. Common commercial cultivars of Cerasus humilis generally have high fruit acidity. Our research group previously constructed a hybrid of the 'Jinou 1' (high acidity) and 'DS-1' (low acidity) cultivars of C. humilis. Here, we conducted quantitative trait locus (QTL) mapping of fruit acidity using 208 F1 progeny of this cross to construct a high-density genetic map. We then used these findings to develop kompetitive allele-specific PCR (KASP) molecular markers. Results collected over 2 consecutive years showed that the hybrid population of 'Jinou 1' × 'DS-1' exhibited a continuous normal distribution of titratable acid content in their fruits, indicating that acidity level was a typical quantitative trait controlled by multiple genes. Stemming from this finding, interval mapping identified 16 QTLs associated with fruit acidity. The phenotypic variation contribution rates ranged from 8.6 to 25%. We then used KASP to develop molecular markers for organic acids, all of which were located to chromosome 1, with genotypes AA and AC representing the high- and low-acid types, respectively. KASP markers were used for genotype validation in 41 different acidic C. humilis varieties (lines) and 3 hybrid populations. This study provides a solid foundation for accelerated, efficient molecular-marker-assisted breeding of C. humilis cultivars which produce low-acidity fruits.