Sucrose and boric acid effects on in vitro pollen viability of Durio zibethinus

Abstract

Durian is a highly valued tropical fruit, but fruit set and seed development remain variable in mixed orchards where cross-pollination depends on viable pollen. In vitro germination provides a functional estimate of pollen viability and can guide controlled pollination and breeding work. This study evaluated the effects of sucrose and boric acid in Brewbaker and Kwack medium on pollen germination and pollen tube growth of normal-seeded durian, and described its basic pollen morphology. Pollen was collected from anthesed flowers of a Duri Hitam durian tree and tested using a factorial completely randomized design with four sucrose concentrations and four boric acid concentrations, with five replications. Pollen morphology was observed using light microscopy, while germination percentage and pollen tube length were measured after dark incubation. Sucrose, boric acid, and their interaction significantly affected germination percentage. The highest germination was obtained in medium containing 16% sucrose and 0.01% boric acid, although this treatment did not differ significantly from several adjacent combinations. Sucrose and boric acid also affected pollen tube length as individual factors, but their interaction was not significant. The longest mean pollen tube was recorded descriptively in the same medium combination. The pollen grains were oblate spheroidal, psilate, and tricolporate. These results indicate that moderate sucrose combined with low boric acid supports functional pollen germination of durian under in vitro conditions, but field pollination tests are still required to verify reproductive success in vivo.