ROOT DEVELOPMENT INITIATED BY EXOGENOUS AUXIN SYNTHESIS GENES IN BRASSICA SP CROPS

Auxin synthesis genes in pRiA4 and pRi1855 were cloned separately in b inary vectors and introduced into Chinese cabbage (Brassica pekinensis ), cabbage (Brassica oleracea var. capitata) and cauliflower (Brassica oleracea var. botrytis). The functions of these genes were investigat ed in root induction, root growth and plant phenotype. Both sets of au xin genes initiated root formation on hypocotyl segments and cotyledon explants after infection by Agrobacterium strains LBA4404auxA and LBA 4404auxB. For Chinese cabbage and cabbage, the root initiation was pol ar since roots proliferated usually on basal ends of the explants. For cauliflower, rooting was not polar in that roots were observed on bot h ends (basal and apical ends) of hypocotyl segments. Addition of 3 mu M indole-3-acetic acid (IAA) to the culture medium resulted in the lo ss of polar rooting of Chinese cabbage and cabbage. Between transforme d root lines and between transgenic plant lines were the considerable difference in growth pattern. The former was classified into four type s according to root length and number of branch roots while the latter sorted into three groups on the basis of plant phenotype. Most of the transgenic plants had slightly wrinkled leaves. The leaf sections, di ssected from transgenic plants, were cultured in the absence of hormon e and rooting was observed for most of transgenic plants. From the pop ulation of transgenic plants, three Lines of Chinese cabbage and cabba ge were screened, that characterized with strong root systems, early i nitiation of leaf heads and fast growth.