Amiprophosmethyl-induced efficient in vitro production of polyploids in raphanobrassica with the aid of aminoethoxyvinylglycine (AVG) in the culture medium.

Optimum conditions for obtaining tetraploid were investigated in raphanobrassica, the intergeneric hybrid between radish (Raphanus sativus) and kale (Brassica oleracea var. acephala) by treating in vitro plants with an anti-mitotic agent, amiprophosmethyl (APM). Initially, no tetraploids but hexaploids and octaploids were induced by the treatments. Although the leaves of these polyploids of raphanobrassica showed chlorosis during subcultures in in vitro conditions, the chlorosis could be successfully prevented by the ethylene inhibitors, both AVG and AgNO3. Based on this result, AVG was added into medium used for the culture after the chromosome doubling treatment, which subsequently resulted in increased survival rates of the treated plant materials as well as increased production rates of polyploids including tetraploid. These polyploid plants showed obviously different characters from the original diploid plant. The tetraploid plant had bigger sizes in shoot, flower and leaf, and more number of leaves than the diploid. On the other hand, the hexaploid and octaploid plants had smaller sizes in shoots and leaves, and less number of leaves than the diploid. Concentration of glucosinolates, functional substances of Brassicaceae crops, did not significantly differ between diploid and tetraploid of raphanobrassica, but reduced in hexaploid and octaploid.

Identification of a triterpenoid saponin from a crucifer, Barbarea vulgaris, as a feeding deterrent to the diamondback moth, Plutella xylostella.

Larvae of the diamondback moth, Plutella xylostella, a crucifer specialist, refuse to feed on a crucifer, Barbarea vulgaris, because of the presence of a feeding deterrent, which is extractable with chloroform. We isolated a feeding deterrent from B. vulgaris leaves, by successive fractionations with silica-gel, ODS, i.e., C18 reversed phase, and Sephadex LH-20 column chromatographies, and ODS-HPLC, guided by a bioassay for feeding deterrent activity. The structure of the compound was determined to be a monodesmosidic triterpenoid saponin, 3-O-[O-beta-D-glucopyranosyl-(1-->4)-beta-D-glucopyranosyl]-hederagenin, based on FAB-MS, 1H- and 13C-NMR spectra, and hydrolysis experiments. When the compound was applied to cabbage leaf disks at greater than 0.18 microg/mm2, consumption of the disks by third instars was less than 11% of control disks treated with the solvent alone. Furthermore, all first instars died on the disks treated with the same concentrations. Because the concentration of the compound in the fresh leaves of B. vulgaris was comparable to the effective dose in the cabbage leaf disk tested, we conclude that the unacceptability of B. vulgaris to P. xylostella larvae is primarily due to this saponin.