Study on triploid breeding in loquat (Eriobotrya japonica Lindley) and technological development for the production of seedless loquat fruit with bioregulator

Fruit in general are considered luxuries in the eating habits of Japan. Most fruit produced locally are consumed as table fruit or gifts for fresh eating. Consumers are inclined to seek fruit of high quality with good appearance and content. They select fruit on the bases of good taste, beautiful appearance, and large size. However, fruit properties related to eating ease such as being seedless, peelability, edible portion, and so on have recently been taken into consideration. As is the case with examples of grape and citrus fruit, being seedless and having few seeds are high added values for fruit and one of important objectives in today's fruit tree breeding. Loquat fruit are about 80 grams at the largest and belong to a group of relatively smaller fruit sizes than other fruit. Because a few large seeds are present in a piece of loquat fruit and their ratio in weight to a whole piece of fruit is extremely high ranging 15-20% when compared with other fruit, seedless loquat fruit are keenly desired by consumers and considered very important from an industrial or research viewpoint. Technological development for the production of seedless loquat fruit is an issue of concern that has been keenly desired by producers and consumers for many years. It has also been an interesting issue for the author, who has been engaged in the cultivation and breeding of loquat. Studies on loquat fruit conversion to seedless fruit started in the 1960's, when attempts to increase the edible portion and decrease the number of seeds in fruit also began. As was the case with seedless grape fruit, technological development for seedless loquat fruit production was advanced for inducing non-spontaneous parthenocarpy by treatments with plant growth regulators. However, because mature seedless fruits were small and high ratios of fruit with seeds were found among the seedless fruit in every study report, the commercially feasible production of seedless loquat fruit was not achieved.