Silver birch (Betula pendula Roth.) culture initiation in vitro and genotype determined differences in micropropagation

Abstract

Micropropagation has several advantages over conventional vegetative propagation methods, but it is limited by genotype responsiveness. We assessed the effect of age of the mother-tree and the time of explant collection on culture initiation, as well as the multiplication ability and effect of different nutrient media and plant growth regulators on silver birch genotypes. Explants collected from 1‐year‐old trees (66%) and explants collected in spring (64–67%) developed a significantly (both p < 0.001) higher proportion of shoots than those from 15‐year‐old trees (39%) and those collected in mid-summer (31%) and autumn (29%), respectively. In a stabilised culture, the length of the main shoot varied from 1.3 to 7.8 cm between genotypes, and the multiplication rate ranged from 1.0 to 6.8 shoots per explant. Hyperhydrated shoots were present in 17 out of 50 clones, and, among the clones, ranged from 14 to 50%. Cultures on the Murashige and Skoog basal medium had a higher multiplication rate than cultures on a Woody Plant Medium, and the application of zeatin provided better results than 6‐benzylaminopurine. The difference between cytokinin types was 11–29% for the multiplication rate and 21–29% for the length of the main stem. The highest multiplication rate was obtained using a zeatin concentration of 0.5 mg L−1. However, better shoot growth and proliferation had a significant positive relation to shoot hyperhydration (all p < 0.001). Therefore, a medium with an optimal balance between the multiplication rate and the number of hyperhydrated shoots should be carefully selected.