Effect of enhanced pollination on economic properties of self-compatible loquat (Eriobotrya japonica Lindl.)

Loquat (Eriobotrya japonica Lindl.), a member of the Rosaceae, carries the RNase-dependent gametophytic self-incompatibility (GSI) fertilization system. However, some cultivars, including the Israeli 'Yehuda' and 'Akko 1', are self-compatible (SC). Since SC cultivars are not dependent on pollen donors, they are usually planted in 'solid blocks'. Nevertheless, in some SC Rosaceae species, such as apricot, cherry and almond, enhanced self- or cross-pollination increases fruit set. To determine whether enhanced pollination can improve 'Yehuda' and 'Akko 1' fruit set and fruit size relative to spontaneous self-pollination, the impact of introducing honey bees and the effect of cross-pollination were examined. We found that honey bees are highly attracted to 'Yehuda' and 'Akko 1' flowers, and fruit size in both cultivars was positively correlated with the number of seeds per fruit. In a net-caged tree experiment, fruit set of 'Yehuda' and 'Akko 1' benefited from the presence of honey bees. However, fruit set was also relatively high for the caged trees without honey bees which underwent spontaneous self-pollination, and commercial fruit thinning was required for all treatments. For both cultivars, seed set after spontaneous self-pollination was the same as for self-pollination in the presence of honey bees. The impact of cross-pollination between different cultivars moderately increased 'Yehuda' fruit set and 'Akko 1' seed set. Taken together, the results suggest that spontaneous self-pollination meets the pollination requirements for the SC loquat cultivars 'Yehuda' and 'Akko 1', and that the presence of pollen donors and/or honey bees confers a minor commercial advantage.