Effect of polyvinyl alcohol on in vitro rooting capacity of shoots in pear clones (Pyrus communis L.) of different ploidy

Poor adventitious root formation is a major obstacle in micropropagation. In this study, intense efforts have been made for improvement of rooting procedures for triploid, tetraploid and mixploid clones of the pear cultivar ‘Fertility' obtained by in vitro colchicine treatment. An efficient rooting procedure has been developed for the pear clones of different ploidy by adding polyvinyl alcohol (PVA) to the rooting medium. PVA significantly improved rooting percentage and root number per plantlet for diploid, triploid and tetraploid clones. However, PVA had little or no effect on rooting capacity of mixploid clones. The efficiency of in vitro rooting in diploid, triploid, tetraploid and mixploid is highly genotype-dependent. In general, diploid was the highest, followed by triploid and tetraploid, mixploid was the lowest.