VERMICULITE-CONTAINING AND GELLAN GUM-SOLIDIFIED MEDIUM IMPROVES ROOTING OF MICROCUTTINGS OF JAPANESE PEAR CULTIVARS
Micropropagation of Japanese pear (Pyrus pyrifolia (Burm. f.) Nakai) has been developed for 20 years. However, rooting of microcuttings is still difficult, and there is no report available in literature on survival of rooted microcuttings following acclimatization, although they grew poorly after potting. Hence, in the present study five Japanese pear cultivars were used with the aim to improve rooting and acclimatization of the microcuttings. Shoots (at least 10 mm long) proliferated on MW medium supplemented with 10 µM BA and 0.5 µM IBA, were isolated from shoot clumps and planted in 1/2 MW with IBA 5 or 10 µM (root-inducing medium). After dark incubation for 5 days, the microcuttings were transferred to the following three kinds of root-developing media with no growth regulators: 1/2 MW medium gelled with gellan gum, 1/2 MW medium plus vermiculite gelled with gellan gum and 1/2 MW liquid medium plus vermiculite. After 16-hour photoperiod incubation for 60 days, the rooted microcuttings were planted in Jiffy pots in polycarbonate vessels and covers, and were gradually acclimatized for 60 days. The vermiculite-containing and gellan gum-solidified medium improved rooting of microcuttings of the difficult-to-root cultivars. The microcuttings of two cultivars did not root in the gellan gum-solidified medium at all. Although the microcuttings planted in the vermiculite-containing and gellan gum-solidified medium did not produce more roots and the total root length was shorter than those in the gellan gum-solidified medium, there was no clear relationship between the root-developing medium and the survival of rooted microcuttings. As a result, the percentages of acclimatized plantlets of the difficult-to-root cultivars tended to be higher when vermiculite-containing and gellan gum-solidified medium was used. The basal medium in the rooting medium affected the rooting of microcuttings, and the percentages of acclimatized plantlets planted in the rooting media saturated with 1/2 WP medium were higher than those with 1/2 MW medium, irrespective of rooting ability.
Tetsumura, T., Ishimura, A., Aikou, Y., Eguchi, N., Kai, Y., Tashiro , K. and Honsho, C. (2011). VERMICULITE-CONTAINING AND GELLAN GUM-SOLIDIFIED MEDIUM IMPROVES ROOTING OF MICROCUTTINGS OF JAPANESE PEAR CULTIVARS. Acta Hortic. 923, 59-64
acclimatization, micropropagation, MS medium, MW medium, Pyrus pyrifolia, WP medium