A STUDY OF SOME FACTORS AFFECTING AGROBACTERIUM TRANSFORMATION AND PLANT-REGENERATION OF DENDRANTHEMA-GRANDIFLORA TZVELEV (SYN CHRYSANTHEMUM-MORIFOLIUM RAMAT)

In an attempt to develop a system for producing transformed plants fro m explants of Dendranthema grandiflora, the susceptibility of the cult ivar Super White to various wild-type strains of Agrobacterium tumefac iens and A. rhizogenes was investigated. Tumour formation was not a re liable indicator of the ability of a related disarmed strain to mediat e transformation. Following inoculation of explants with disarmed Agro bacterium strains, a number of shoots developed on selective media. Ho wever, none of these shoots were transformed. By co-cultivating stem i nternode explants with a mixed inoculum of wild-type and disarmed stra ins, it was possible to obtain a callus stably transformed with Agroba cterium carrying a disarmed T-DNA. Histological analysis of explants r evealed that shoot regeneration initially occurred from the cells of t he epidermis and subsequently from the cortex. However, the cells whic h were susceptible to T-DNA transfer were confined to the vascular tis sue.