Sugar content is one of the most important quality traits of tomato. Cell wall invertase promotes sucrose unloading in the fruit by maintaining a gradient of sucrose concentration between source leaves and fruits, while invertase inhibitor (INVINH) regulates this process. In this study, knock-out of cell wall INVINH in tomato (SlINVINH1) was performed by genome editing using, CRISPR/Cas9 and Target-AID technologies. Most of the genome-edited lines set higher soluble solid content (SSC) fruit than the original cultivar ‘Suzukoma’, while fruit weight was different among the genome-edited lines. From these genome-edited lines, three lines (193–3, 199–2, and 247–2), whose SSC was significantly higher than ‘Suzukoma’ and fruit weight were almost the same as the original cultivar, were selected. The fruit weight and overall plant growth of the two lines were comparable to those of the original cultivar. In contrast, the fructose and glucose contents in the mature fruits of the two lines were significantly higher than those of the original cultivar. The mature fruits of genome edited line 193–3 showed the highest sugar content, and the fructose and glucose contents were 29% and 36% higher than that of the original cultivar, respectively. Whole genome sequence data showed no off-target mutations in the genome-edited lines. Non-target metabolome analysis of mature fruits revealed that fructose was the highest loading factor in principal component analysis (PCA) between the genome-edited line and the original cultivar, and no unexpected metabolites appeared in the genome-edited line. In this study, we succeeded in producing tomato lines with high sugar content without a decrease in fruit weight and deterioration of plant growth by knock-out of SlINVINH1 using genome editing technology. This study showed that functional disruption of SlINVINH1 is an effective approach to produce tomato cultivars with high sugar content.

Plant secondary metabolites exhibit various horticultural traits. Simple and rapid analysis methods for evaluating these metabolites are in demand in breeding and consumer markets dealing with horticultural crops. We applied probe electrospray ionization (PESI) to evaluate secondary metabolite levels in horticultural crops. PESI does not require pre-treatment and separation of samples, which makes it suitable for high-throughput analysis. In this study, we targeted anthocyanins, one of the primary pigments in horticultural crops. Eighty-one anthocyanins were detected in approximately 3 minutes in the selected reaction-monitoring mode. Tandem mass spectrometry (MS/MS) could adequately distinguish between the fragments of anthocyanins and flavonols. Probe sampling, an intuitive method of sticking a probe directly to the sample, could detect anthocyanins qualitatively on a micro-area scale, such as achenes and receptacles in strawberry fruit. Our results suggest that PESI/MS/MS can be a powerful tool to characterize the profile of anthocyanins and compare their content among cultivars.