Abstract
By backcrossing to Raphanus sativus cv. ‘Pink ball’, 55 BC2 plants were obtained from two sesquidiploidal BC1 plants (MaRR, 2n = 32) between Moricandia arvensis (MaMa, 2n = 28) and R. sativus (RR, 2n = 18). Their somatic chromosome numbers ranged from 2n = 18 to 2n = 23, except for one hyperploid plant with 2n = 44. In the BC3 generation, 64 plants (2n = 19) were generated from 16 BC2 plants with 2n = 19~23. Each plant with 2n = 19 exhibited both morphological and physiological characteristics diagnostic for the presence of an added chromosome of M. arvensis genome, and showed predominantly the chromosome pairing type of 9II + 1I at metaphase I of PMCs. They were classified into twelve (a~l) types of monosomic chromosome addition lines (MALs) of alloplasmic (M. arvensis) R. sativus carrying M. arvensis cytoplasm by their morphological, physiological and cytogenetical characteristics. The mean of seed setting in the twelve types of MALs ranged from 2.88 grains (f-type) to 0.51 grains (j-type) per pollinated flower when they were backcrossed to R. sativus cv. ‘Pink ball’. The transmission rates to the next generation through female gametes ranged from 32.5 % (f- and j-types) to 5.5 % (h-type) when smaller seeds were selectively grown. The specific characteristics of each type of MALs were transmitted from the BC3 generation to the BC4 and BC5 ones without any modification. The MALs of the distinctive twelve types were also identified using RAPD markers in the BC5 generation. Pollen fertility of the twelve types of MALs ranged from 85.6 % (c-type) to 3.4 % (l-type), although four types (g-, h-, i- and j-types) exhibited complete male sterility. Furthermore, alloplasmic (M. arvensis) R. sativus plants (2n = 18) which were derived from male fertile MALs showed complete male sterility. The twelve types of MALs produced in this study should be useful materials to determine the localization of genes for agronomic traits on the individual chromosome of M. arvensis and the alloplasmic (M. arvensis) R. sativus should also be a useful material for the development of a new cytoplasmic male sterility system in R. sativus.
