Radish, Raphanus sativus L., is an annual vegetable belonging to the family Cruciferae and is a traditionally important vegetable in many countries. The enlarged root and hypocotyl of radish are consumed mainly as a salted vegetable and are also eaten fresh as grated radish, garnish, and salad.
Radish has been cultivated and consumed as a part of the eastern Asian diet. Recent advances in cultivation technique require more promising varieties of radish that can resist the problems of disease and insects and can meet a more varied range of dietary demands. This chapter presents an overview of the germplasm resources and cytogenetics of radish. It discusses the present state of radish breeding, mainly in Japan.
For radish, breeding work has been carried out on ecological traits, resistance to diseases, and adaptability for different kinds of consumption. The ecological traits are productive and qualitative characteristics such as high yielding ability, early maturity, late bolting, edible quality (pungency),
late pore formation, cold-hardiness, drought resistance, heat tolerance, wet tolerance, soil adaptability, and so on. Virus disease, yellows, soft rot, downy mildew, grey leaf spot, and other diseases are prevalent in Japan. Radish is mainly consumed fresh, boiled, or salted or as dried strips or seedlings (kaiware).
Radish is an allogamous plant exhibiting a high level of self-incompatibility and shows inbreeding depression when self-propagation by bud pollination is repeated. It is difficult to obtain a large amount of seed mainly because of the limited seed numbers produced per pod. In this case,
F1 hybridization combined with self-incompatibility and heterosis is a helpful breeding method. There are three methods of seed production in F1 hybridization: (1) single crossing, (2) three-way crossing, and (3) double crossing. The chapter describes the double crossing method, which is the most effective means of seed production in radish.
