Male functionality inGarcinia celebicaL., a candidate ancestor species of mangosteen (G. mangostanaL.)

Abstract

Mangosteen (Garcinia mangostana L.) is widely cultivated for its prized fruit, but its origins are unclear as this crop has not been found in the wild. Seashore mangosteen (Garcinia celebica L.) has been proposed as a candidate ancestral species for the mangosteen male parent in a hypothesized hybridization event, yet the functionality of the male organs in perfect flowers of G. celebica has not been characterized. The objective of this study was to describe pollen development in G. celebica using light, scanning, and transmission electron microscopy techniques. Male gametophyte development led to viable pollen at anthesis. The tapetum was of the secretory type, and it started to degrade following meiosis II, which corresponded to the complete encasement of a callose wall around the microspore tetrad. Pollen viability, demonstrated with 2,3,5-triphenyl tetrazolium chloride (TTC) assays, was 68%. An in-vitro pollen germination assay was developed, and the rate of germination was remarkably similar to the viability (68%). Male functionality was clearly confirmed by both the high rate of pollen viability and germination. The occurrence of stigmatic exudates on pistillode and its pollen features are consistent with biotic pollination. The perfect flower of G. celebica is thus a functional male flower.