Studies on the breeding of artificially synthesized rape (Brassica napus). I. F₁ hybrids between B. campestris group and B. oleracea group and the derived F₂ plants.

Abstract

This report concerns the result of observations during 1950∼1960 on interspecific hybrids (F₁ and F₂) obtained fram 11, 505 crosses between n=10 group (Brassica campestris) and n=9 group (B. oleracea) with the purpose of synthesizing a new type of Napus. Five interspecific hybrids were obtained as shown in Tables 3 and 4. Two were obtained from bud pollination in 1952 and the other two wete from the double pollination method in 1957 and the last one was obtained by means of a dead pollen mixture pollination in 1957. The author assumes that vital or dead pollen of the mother plant on its stigma must be stimulant in pollen germination and their tube elongation when interspecific crossing occurs. F₁ hybrids were named CO-1, -2, -3, -4 and -5. Chromosome numbers of CO-1∼-4 were all 2n=19 and CO-5 was 2n=29 (Figs. 1, 7, 8, 9 and 13, Photoes. 1, 2, 3, 4 and 5) . The former were derived from conjugation of chromosomes of the parents (n=10 and n=9), and the latter from conjugation of 20 chromosomes from 4X mother plant and 9 chromosomes from 2X father plant.