Yasuo Matsuzawa

Radish: Raphanus sativus L.

Publisher Summary 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, F 1 hybridization combined with self-incompatibility and heterosis is a helpful breeding method. There are three methods of seed production in F 1 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.

Structural and Biochemical Dissection of Photorespiration in Hybrids Differing in Genome Constitution between Diplotaxis tenuifolia (C3-C4) and Radish (C3)

We compared the structural, biochemical, and physiological characteristics involved in photorespiration of intergeneric hybrids differing in genome constitution (DtDtR, DtDtRR, and DtRR) between the C3-C4 intermediate species Diplotaxis tenuifolia (DtDt) and the C3 species radish (Raphanus sativus; RR). The bundle sheath (BS) cells in D. tenuifolia included many centripetally located chloroplasts and mitochondria, but those of radish had only a few chloroplasts and mitochondria. In the hybrids, the numbers of chloroplasts and mitochondria, the ratio of centripetally located organelles to total organelles, and the mitochondrial size in the BS cells increased with an increase in the constitution ratio of the Dt:R genome. The P-protein of glycine decarboxylase (GDC) was confined to the BS mitochondria in D. tenuifolia, whereas in radish, it accumulated more densely in the mesophyll than in the BS mitochondria. In the hybrids, more intense accumulation of GDC in the BS relative to the mesophyll mitochondria occurred with an increase in the Dt:R ratio. These structural and biochemical features in the hybrids were reflected in the gas exchange characteristics of leaves, such as the CO2 compensation point. Our data indicate that the leaf structure, the intercellular pattern of GDC expression, and the gas exchange characteristics of C3-C4 intermediate photosynthesis are inherited in the hybrids depending on the constitution ratio of the parent genomes. Our findings also demonstrate that the apparent reduced photorespiration in C3-C4 intermediate plants is mainly due to the structural differentiation of mitochondria and chloroplasts in the BS cells combined with the BS-dominant expression of GDC.

Inheritance of C3-C4 Intermediate Photosynthesis in Reciprocal Hybrids between Moricandia arvensis (C3-C4) and Brassica oleracea (C3) that Differ in their Genome Constitution

Abstract To Elucidate The Genetic Mechanisms Underlying C3―C4 intermediate Photosynthesis, We investigated The Structural and Photosynthetic Characteristics of Leaves of Reciprocal Hybrids Between The C3―C4 intermediate Species Moricandia Arvensis (L.) Dc. (Mama) and The C3 Species Brassica Oleracea L. (Cabbage; Cc), Which Differ in Genome Constitution. Moricandia Arvensis Bundle Sheath (Bs) Cells included Many Centripetally Located Chloroplasts and Mitochondria, Whereas Those of Cabbage Had Few Organelles. Hybrid Leaves Were Structurally intermediate Between Those of The Parents and Showed Stronger intermediate C3―C4 Features As The Proportion of The Ma Genome increased. The P-Protein of Glycine Decarboxylase (Gdc) Was Confined Mainly To Bs Mitochondria in M. Arvensis, But Accumulated More in The Mesophyll (M) of Cabbage. in The Hybrids, The Accumulation of Gdc in Bs Cells increased With An increasing Ma:C Ratio. Hybrids Exhibited Gradients in Structural and Biochemical Features, Even in Reciprocal Crosses. The Co2 Compensation Point of Reciprocal Hybrids With High Ma:C Ratios Was Lower Than That of Cabbage But Higher Than That of M. Arvensis. Thus, The Structural and Biochemical Features in Hybrid Leaves Reduced Photorespiration. Moricandia Arvensis Had A Higher Photosynthetic Rate Than Cabbage, But The Photosynthetic Rates of Hybrids Were intermediate Between Those of The Parents Or Comparable To That of M. Arvensis. Our Results Demonstrate That The C3―C4 intermediate Characteristics Are inherited Based On The Ratio of The Parent Genomes, and That There Is No Evidence of Cytoplasmic inheritance in These Characteristics.