THE USE OF LIQUID POLLEN EXTENDER THICKENED WITH POLYSACCHARIDES FOR ARTIFICIAL POLLINATION OF KIWIFRUIT

Artificial pollination is essential in Japan to produce kiwifruit of marketable size and shape. To reduce labour requirements during production, it is important to increase the efficiency of pollination. With artificial pollination, use of a liquid pollen extender has provided a convenient (Hopping, 1982), but expensive option. This study aimed to develop a liquid extender that is relatively cheap, is easy to prepare and is effective for artificial pollination of kiwifruit by selecting appropriate thickening agents. Agar, -, - and -carrageenan, guar gum, locust bean gum, xanthan gum and pectin were used as thickening agents of the liquid extender containing 0.2 M monosaccharide or sucrose. To evaluate the stability of dispersion of ‘Tomuri’ pollen in the liquid, changes in absorbance at 400 nm were measured after suspending pollen in the liquid. Germination rates of pollen suspended in the extenders was determined on agar medium. Flowers of ‘Hayward’ were pollinated with pollen suspension thickened with agar, and fruit growth, number of seeds per fruit and fruit quality attributes were examined. Agar, -carrageenan, guar gum and xanthan gum were effective in maintaining uniform dispersion of pollen in the extender solution. The thickening agents, except for pectin, did not inhibit pollen germination. There were no significant differences in fruit characters between liquid extender thickened with agar and the powder. Fruit size decreased with increasing rate of dilution more than 1:500 (1 g pollen in 500 ml extender). In conclusion, the use of liquid pollen extender thickened by polysaccharides could be applicable for artificial pollination of kiwifruit. The cost of producing the extender is relatively low and growers could prepare it themselves.