Delayed Senescence in Cauliflower Transformed with an Autoregulated Isopentenyl Transferase Gene

Abstract

Cauliflower (Brassica oleracea var. botrytis) was transformed, using Agrobacterium tumefaciens, with an autoregulated isopentenyl transferase (ipt) gene under the control of a senescence‐associated gene promoter, pSAG12, isolated from Arabidopsis thaliana. The effect of introducing this chimeric construct on cytokinin (CK) content, chlorophyll retention, and plant morphology and development were investigated. A range of CK and chlorophyll contents was found among the individual primary transformants. Progeny were studied from one of the primary transformed lines that did not have elevated cytokinin content and was phenotypically similar to the parent line but displayed delayed leaf senescence. The pSAG12:ipt gene was inherited in a Mendelian manner, and the effect of this gene on senescence‐related parameters was observed in a number of the progeny. While the pSAG12:ipt progeny did exhibit delayed leaf senescence, it was accompanied by undesirable agronomic traits, including less synchronous curd initiation, smaller curd size, and greater susceptibility to fungal infection.