Hormone Analysis in the Locule of Mangosteen Fruit during Apomictic Seed Development

Mangosteen (Garcinia mangostana L.) is one of the most commercially important fruit crops in Thailand. It is mainly consumed fresh and favored by everyone due to its delicious taste. Mangosteen produces apomictic seeds and it has been suggested that all mangosteen trees originated from a single clone as it is reproduced apomictic seed as the result of apomixis. Seed of mangosteen also has a unique feature; there is no embryo in the seed. Usually, there are 4-7 locules in mangosteen fruit but only 1-3 locules contain perfect seeds. In the young developing ovule in the locule, there are endosperm liquids and protuberance derived from outgrowth of integument cells that develop to an apomictic seed. In this study, we analyzed the hormones of the liquid in well-developed ovule to find out the role of hormones that may be able to promote apomictic seed growth and development in mangosteen fruit. The 5 ml of liquid from well-developed ovule was collected at 6 or 8 weeks after blooming. IAA, cis, trans-ABA and jasmonic acid were identified and estimated by using a gas chromatography-mass spectrometry (selected ion monitoring, GC-SIM) with internal standards of their deuterium compounds. The results showed that the liquid from 6 weeks after blooming contained IAA, cis, trans-ABA and jasmonic acid at the level of 93.1, 7.3 and 228.1 ng ml(-1), respectively. While the amounts of IAA, cis, trans-ABA and jasmonic acid at 8 weeks after blooming were 30.4, 10.2 and 54.5 ng ml(-1), respectively. Sugar content in the liquid was also analyzed and the results showed that fructose and glucose contents increased rapidly from 8 week after blooming.