Intraspecific genetic variation in cytokinin-controlled shoot morphogenesis from tissue explants of Petunia hybrida

In this paper we present the characterization of a differential morphogenetic response to cytokinin between two Petunia lines cultured in vitro. In particular, we report that: (1) two inbred cultivars of Petunia hybrida differed in the concentrations of cytokinin required to induce shoot morphogenesis from leaf explants and from stem epidermal explants in vitro. These differences were specific to the particular cytokinin utilized. (2) The F₁ hybrids of the two cultivars exhibited a biphasic morphogenetic response to cytokinin which was unlike that of either parent. (3) The cytokinin dose responses were similar in the reciprocal F₁ hybrids, indicating that the response is controlled primarily by Mendelian genes, rather than by cytoplasmic factors.