Effect of abyssinian mustard cytoplasm on CC genome of Brassica.

Abstract

Abyssinian mustard (Brassica carinata BRAUN, BC genomes 2n=34) was repeatedly backcrossed with broccoli Green Comet (F1 hybtids) (B.oleracea L.var.italica PLENCK, C genome, 2n=18). In the process of cytoplasm-substitution (Fig. 1), seed fertility in plants increased exponentially as their chromsome numbers became nearer to 2n=18 (Fig. 2). In B2 generation, plants with 2n=18 chromosomes were obtained. Juging from their chromosome association of 9II, they were assumed to be C genome plants with Abyssinian mustard cytoplasm. Then these 2n=18 Plants with Abyssinian mustard cytoplasm were reciprocally crossed with broccoli plants with normal cytoplasm. Through the comparison of some characters between these reciprocal F1 plants, alloplasmic effect on broccoli was examined. It was found that alteration of flower shape and male sterility which appeared in cytoplasm-substituted plants were the effect of Abyssinian mustard cytoplasm (Tables 1, 2 and Fig. 3). Photosynthetic rate and chlorophyll content were lower in alloplasmic plants than in normal plants (Table 3 and Fig. 4). Alloplasmic plants were more severely damaed than normal cytoplasmic plants when they met accidental one-night cold-waves (-5∼-6'C, ca. 8h) (Table 4). Therefore, cold tolerance which is universal in C-genornic species of Brassica may be concerned with not only nucleic genes but also cytoplasmic factors.