MICROPROPAGATION AND STRAWBERRY PLANT QUALITY
Development and homogeneity of plants were quite good in nurseries but heterogeneity between plants occurred in the following years with the appearance of physiological disorders which increased as fruits matured. Many plants collapsed at that time.
Since detailed analyses did not reveal any specific fungal disease, in vitro techniques were suspected of generating bad plant materials. Preliminary comparative trials between standard and micropropagated plants had indicated that highly subcultured clones were the most heterogeneous and highly sensitive to mildew, had bad root systems and decreased fruit size and weight.
In order to compare standard and vitro plants, our group has produced and studied materials obtained by both methods but from the same mother plant. No difference has so far been observed between vitroplants subcultured 4, 7, 10 and 19 times on the one hand and between in vitro and standard plants on the other (cv. Gorella and Belrubi).
By halving the concentrations of cytokinin and auxin used in the Boxus medium (0.5 mg l-1 instead of 1 mg) and by limiting the number of subcultures to 10, France produced new mother plants in 1985. Such vitroplants expressed a better resistance than standard plants to frost damages due to the extremely cold 1986 and 1987 winter periods.