FruitPhenoBox – a device for rapid and automated fruit phenotyping of small sample sizes

Abstract Background: Fruit appearance of apples is cultivar-specific and one of the main criteria for consumer choice. Consequently, appearance is an important selection criterion in the breeding of new cultivars. It is also used for the description of older varieties or landraces. In commercial apple production, sorting devices are used to classify a high number of fruits from a few cultivars. In contrast, the description of fruits from germplasm collections or for breeding is based on a few fruits from many cultivars and is mostly performed visually by pomology experts. Therefore, such visual ratings are laborious, often difficult to compare and remain subjective. Results: Here we report on a morphometric device, called the FruitPhenoBox, for automated fruit weighting and appearance description using computer-based analysis of five images per fruit. The recording of approximately 100 fruits each from 15 apple cultivars using the FruitPhenoBox was achieved rapidly, with an average handling and recording time below eleven seconds per fruit. The comparison of the fruits from the 15 apple cultivars identified significant differences in shape index, fruit width, height and weight. Fruit shape was characteristic for each cultivar, while fruit coloration showed larger variation within sample sets. Assessing a subset of 20 randomly selected fruits per cultivar, fruit height and width were described with a relative margin of error of 2.6% and 2.1% and 6.2%, respectively, calculated from the mean value of all available fruits. Conclusions: The FruitPhenoBox allows for the rapid and consistent description of fruits of a single apple genotype. By relating the relative margin of error for fruit width, height and weight description with different sample sizes, it was possible to determine an appropriate fruit sample size to efficiently and accurately describe the recorded traits. Therefore, the FruitPhenoBox is a useful tool for breeding and the description of apple germplasm collections.