Effect of Dwarfing Induced by Uniconazole-P on Snow Tolerance of the Faba Bean (Vicia faba L.)

Abstract

To clarify the effect of artificial dwarfing induced by uniconazole-P, a gibberellin biosynthesis inhibitor, on the snow tolerance of faba bean, we examined the snow damage, non-structural carbohydrate (NSC) concentration, and resistance to snow molds of the seedlings treated with uniconazole-P. Artificial dwarfing markedly decreased snow damage caused by continuous snow cover for 62 days. NSC concentration, which affects physiological snow tolerance and snow mold resistance, was lower in dwarfed plants than in non-dwarfed plants. However, there was no difference in the rate of decrease of NSC concentration between dwarfed and non-dwarfed plants under cold and dark conditions simulating snow cover. In inoculation tests, the lesions of Pythium iwayamai and Sclerotinia trifoliorum on the leaves detached from dwarfed plants were shorter than those on the leaves from non-dwarfed plants. In artificially dwarfed plants, the leaves were thicker and darker in color, and mesophyll cells were larger and denser than those in the non-dwarfed plants. Our findings suggest that the artificial dwarfing caused by uniconazole-P increased the resistance of the leaves to snow molds, thereby increasing snow tolerance, without increasing NSC concentration. The microstructural changes that occur with dwarfing may be a factor in snow tolerance.