TEMPORAL COMPETENCE FOR TRANSFORMATION OF LYCOPERSICON-ESCULENTUM (L-MILL) COTYLEDONS BY AGROBACTERIUM-TUMEFACIENS - RELATION TO WOUND-HEALING AND SOLUBLE PLANT FACTORS

A competency window for transformation of tomato cotyledons by Agrobacterium tumefaciens was established. In vitro, tomato cotyledons could be transformed over a long time interval after wounding, although the highest transformation competency occurred during the first 24 h interval after wounding. Exogenous virulence gene-inducing factors (50-mu-M acetosyringone or a chloroform-soluble factor from tomato leaves) could be used to reverse the decline in transformation competency up until 96 h post-wounding. A safranin-o stained material (found to contain fatty acids characteristic of suberin) was deposited by 96 h after wounding and thus, may contribute further to the decreased transformation observed after 96 h by presenting a physical barrier to infection. However, there was still transformation after suberization as up to 50 per cent of the explants exposed to bacteria were transformed.