Selectivity of auxin for induction and growth of callus from excised embryo of spring and winter wheat

Abstract

The callus-promoting activity of most commonly known as well as some rarely tested auxins was compared with that of 2,4-dichlorophenoxyacetic acid (2,4-D) for in vitro culture of the excised embryo of spring and winter wheat (Triticum aestivum L.), cv. Chinese Spring and cv. Fredrick. Different auxins in a concentration range from 1 to 50 μM showed widely different activities. Also the two wheat cultivars responded differently to the auxins. When rapid callus formation with limited root growth was used as the basis for comparison, 2-(2-methyl-4-chlorophenoxy)propionic acid (2-MCPP), α-naphthaleneacetic acid, 3,6-dichloro-2-methoxybenzoic acid (dicamba), 4-amino-3,5,6,trichloropicolinic acid (picloram), γ-(2,4-dichlorophenoxy)butyric acid, 2,4,5-trichlorophenoxyacetic acid, and 2,4,5-trichlorophenoxypropionic acid, in the order of effectiveness, were superior to 2,4,-D for callus induction from the embryo of 'Chinese Spring,' although the concentration required was higher than that of 2,4-D. For the winter wheat 'Fredrick,' however, only picloram, dicamba, and 2-MCPP performed as well as 2,4-D. All auxins tested promoted shoot growth; 2-methyl-4-chlorophenoxypropionic acid was most effective for 'Chinese Spring,' whereas picloram was most effective for 'Fredrick.'