PRODUCTION OF INTERGENERIC HYBRIDS BETWEEN RAPHANUS AND SINAPIS AND THE CYTOGENETICS OF THEIR PROGENIES

Reciprocal crosses were made to analyze the intergeneric crossability and to obtain intergeneric hybrids between Raphanus sativus and four S inapis species (S, abba, S, arvensis, S, pubescens and S, turgida). Po llen germination in the pistil and development of hybrid embryos depen ded on the direction of each cross. The crossability was relatively hi gher when Sinapis species were used as pistillate parents, whereas S. pubescens was compatible with R, sativus only when used as pollen pare nt, By embryo rescue technique and/or conventional method, hybrid plan ts were produced in all intergeneric crosses between een R, sativus an d four species of Sinapis except for the cross of S, pubescens x R. sa tivus due to strong pre-fertilization barriers. When Sinapis species w ere used as pistillate parents, 172 F-1 hybrid plants were obtained th rough ovary culture followed by embryo culture. Using R, sativus as pi stillate parent, 12 F-1 hybrid plants were obtained by embryo culture. Exceptionally a few F-1 hybrid plants were obtained from the cross of R, sativus x S. pubescens through ovary culture followed by embryo cu lture. In the cross of S. turgida x R, sativus, a number of seeds harv ested by conventional method developed to F-1 hybrid plants. These res ults indicate the effectiveness of selective application of embryo res cue techniques for the production of hybrids in distant crosses depend ing on the characteristics of crossability between the two parent spec eis. In the cross of Sinapis species x R, sativus, 20 F-1 hybrid plant s exhibited the (0-1)(III) +(0-7)(II) + (4-18)(I) chromosome associati on type at MI. Eight F-1 hybrid plants in the reciprocal cross exhibit ed (0-5)(II) + (8-18)(I) at MI. The occurrence of trivalents and more frequently of bivalents could be attributed in part to allosyndesis. N o differential level in chromosome association in the reciprocal hybri ds could be detected. Hybrid plants in the present study could become promising materials for the breeding of alloplasmic lines, alien-chrom osome addition lines and novel amphidiploids between genus Raphanus an d Sinapis.