Breeding of Tomato with High L-Ascorbic Acid Content by Clonal Selection

Abstract

We developed a variety of tomato with high L-ascorbic acid (AsA) content by clonal selection. Initially, 432 breeding materials of tomato (Lycopersicon esculentum Mill.), were evaluated for the following parameters, fruit ascorbic acid (AsA) content, total soluble solids (TSS) content of fruit homogenate, and fruit weight. Their AsA contents ranged from 28 to 639 mg · kg−1; the average was 247 mg · kg−1. Although no clear correlation between fruit AsA content and average fruit weight existed, many varieties with extremely high AsA content bore small fruit weighing less than 10 g. However, several varieties weighing 30-60 g had AsA content higher than 500 mg · kg−1. Moderate positive correlation was observed between AsA content and TSS content, suggesting a probability of developing tomato varieties with high AsA content and TSS. From these breeding materials, 22 and 53, maternal and paternal parents, respectively, were hybridized, resulting in 698 cross combinations. Among their progenies, 10 or 20 individuals from each cross combination were cultured and evaluated for the above characteristics. The average AsA content ranged from 132 to 388 mg · kg−1. Twenty-four outstanding individuals including VT8 that was finally released as a new variety, were selected and multiplied vegetatively and the clones were evaluated under three cropping types: normal, retarding and forcing culture in several farms in Japan using the ‘House Momotaro’ and ‘Momotaro-York’ two common varieties, as the controls. Although AsA content of VT8 fluctuated from 220 to 365 mg · kg−1, it consistently exceeded that of the control by 50-100%. TSS content of VT8 varied between 5.2 and 7.2%, in contrast to 4.5 to 6.7% of the control. Average fruit weight of VT8 varied with the cropping type from 57.6 to 72.8 g. Yields of VT8 in retarding culture at three different farms were similar to or slightly higher than those of the control varieties. Thus, VT8 was developed as a variety within three years from evaluation of breeding materials to completion of a year-round trial.