EFFECT OF DROUGHT STRESS ON CONTENT AND COMPOSITION OF SEED ALKALOIDSIN NARROW-LEAFED LUPIN, LUPINUS-ANGUSTIFOLIUS L

The effect of drought stress at three growth stages on seed alkaloid c ontent in two sweet (W26 and Polonez) and one bitter variety (Zubr) of spring sown Lupinus angustifolius L. was investigated in a lysimeter experiment on sandy soil in Denmark. Full irrigation resulted in mediu m alkaloid content. Drought stress during the vegetative phase increas ed alkaloid content to 0.094, 0.192 and 2.55% of seed dry matter, resp ectively. At the flowering stage alkaloid content decreased to 0.070, 0.152 and 1.99%, while drought stress during pod-filling increased alk aloid content for the determinate variety W26 to 0.097%, but decreased it to 0.161 and 1.98% for the two indeterminate varieties Polonez and Zubr, respectively. Drought during either flowering or pod-filling re sulted in an increased mean seed weight and a reduced number of seed p er square metre. Alkaloid content was negatively correlated to seed we ight. The alkaloid composition differed for the three genotypes, and w as affected by drought treatment. Compared to the bitter variety the s weet varieties were characterized by reduced concentrations of lupanin , 13-hydroxylupanin and angustifolin, whereas spartein, isolupanin and isoangustifolin were little affected. (C) 1997 Elsevier Science B.V.