The use of digital cameras in plant phenotyping studies using RGB sensors has increased. However, the need for standardization has become apparent because of the diverse analytical approaches used by individual researchers. In this study, we optimized the image acquisition conditions for apples, including scaling tool positioning, lighting conditions, and background color selection. In addition, we developed an ImageJ-based automated image acquisition and analysis program. We generated 240 images of four apple cultivars (Hongan, Hongro, Fuji, and Hwangok) and used 12 image indices to analyze the fruit size, width, length, and shape. We measured the accuracy by comparing the results with actual measurements. Significantly high correlation values were observed between fruit width and the major index (R²=0.947-0.993) as well as between fruit length and the height index (R²=0.964-0.984) based on the analysis using R-squared values to assess accuracy. These findings are expected to enhance the efficiency of apple fruit sorting in the future and can be applied to investigate the shapes of other fruits.

The purpose of this study was to examine the potential utility of marker-assisted selection (MAS) based on storability-associated molecular markers in apple breeding and to provide genotype information for the markers Md-ACS1, Md-ACO1, and Md-PG1 in apple genetic resources as basic data for the use of breeding materials. We analyzed 750 apple genetic resources to assess the allelic composition of Md-ACS1 and Md-ACO1, which play roles in the ethylene biosynthesis pathway, and Md-PG1, which is involved in cell wall degradation. For 108 of the genetic resources used for genotyping, we measured fruit firmness using a texture analyzer (10 mm plunger) at harvest and after 20 days of room temperature (20~25℃) storage. Md-ACS1 and Md-PG1 were found to be associated with changes in fruit firmness (the difference between firmness at harvest and after storage), with ACS1-2/2, PG1-1/1, and PG1-2/2 showing the lowest changes in fruit firmness. In addition, we found that changes in fruit firmness were smallest in late-harvest species, even for the same genotype. In contrast, Md-ACO1 appeared to be unrelated to the storability of fruit. Of the 750 apple genetic resources screened, the genotypes ACS1-2/2, and PG1-1/1 or PG1-2/2 were detected in 3.6% of accessions, including ‘Fuji’, bud mutation cultivars of ‘Fuji’, ‘Chubu’, and ‘Iwakami’. The Md-ACS1 and Md-PG1 markers could have potential utility in assessments of storability and applied in MAS to improve the efficiency of apple breeding.