A cytokinin-resistant mutant of Nicotiana plumbaginifolia is wilty.

Selection for cytokinin resistance by incubating M2 seed of Nicotiana plumbaginifolia, after ethylmethanesulphonate mutagenesis, on 20 μM 6-benzylami-nopurine resulted in the isolation of a monogenic, recessive mutant, CKR1. Germination of the mutant is less sensitive to cytokinin inhibition than the wild type, and leaf development of the mutant occurs at cytokinin concentrations inhibitory to the wild type. Germination of the mutant is also resistant to auxin but not to abscisic acid. Three other traits jointly inherited with cytokinin resistance in the F2 are lack of root branching, precocious germination and wiltiness. The wilty phenotype is the consequence of the failure of stomatal closure during water stress.