Carry-over of Morphological and Biochemical Characteristics Aßociated with Hyperflowering of Micropropagated Strawberries

Abstract

Strawberry plants issued from shoots raised after a high number of subcultures (HNS) in vitro, which were previously characterized by an abnormal hyperflowering process ex vitro, were multiplied conventionally through runners for 8 generations, and then meristem tips re-entered in vitro for a low number of shoot subcultures (LNS). Such HNS-LNS vitroplants flowered abnormally abundantly as compared with always conventionally propagated N-LNS vitroplants, thus self-perpetuating a long term memory of an abnormal developmental pattern. The HNS-LNS hyperflowering vitroplants were also characterized by a carry-over of other biological (reduced growth habit), morphological (reduced hairiness and deposition of epicuticular wax, unifoliolate leaves prevailing) and biochemical (higher peroxidase activity) traits. They also proliferated in vitro at higher rates, which corresponded to higher endogenous levels of cytokinins and higher cytokinin/auxing ratios. Unifoliolate leaves and high cytokinin/auxin ratios are recognized criteria of rejuvenation. These characteristics of HNS strawberry vitroplants are carried-over in the next generations through heritable gene expression.