Comparison of the rheological and diffusion properties of some gelling agents and blends and their effects on shoot multiplication

The rheological and diffusion properties of blends of agar/guar gum, agar/Phytagel and Phytagel/guar gum were analysed and compared to those properties of agar or Phytagel applied alone at two different gelling concentrations. Moreover, their effects on the shoot multiplication of the apple scion Galaxy and two black locust clones (SF63, SF82) were studied, and their cost benefits over agar were calculated. Elastic hydrogel formation was demonstrated for each blend by rheological measurements, but the gel strength depended on the types and concentrations of the applied gelling agents and blends. Guar gum was able to speed the diffusion in the different blends, and diffusion was independent of gel strength. The rate of shoot multiplication increased (to 8.9 shoots per explant) and the percent of hyperhydrated shoots decreased (to 12%) when the blend of agar/guar gum was used for the shoot multiplication of apple. Similarly, the highest multiplication rates of black locust clones (between 3.9 and 4.1) were obtained on media solidified by blends containing guar gum. The best shoot performance with the lowest percent of hyperhydrated shoots (11–12% in SF63 and 2–23% in SF82) was achieved using agar alone or the agar/guar gum blend. The shoot multiplication was improved of both species and the production cost was reduced by 42% by using the agar/guar gum blend.