Physiological changes in pre-harvest dropped fruits in the pummelo cultivars ‘Thong Dee’ and ‘Khao Nam Phueng’

Abstract

This investigation of physiological changes in pummelo pre-harvest dropped fruit, termed “yellow fruit calyx symptoms” in Thailand, aimed to examine in two particular cultivars Thong Dee and Khao Nam Phueng grown in the central regionof Thailand. The results show that the normal pummelo fruits of either variety had statistically more total non-structuralcarbohydrate (TNC) in their peel and pulp than did those of the dropped fruits. On the other hand, the leaves of normal fruittrees of both cultivars show less TNC than those found in the leaves of pre-harvest dropped fruit trees. There were significantdifferences in some plant nutrients in the leaves, peel and pulp of the dropped and normal pummelo cultivars. IAA concentration in fruit was determined with the result that normal fruits had a statistically higher IAA concentration than did those inpre-harvest dropped fruits. The PCR technique used for the greening disease test identified infections in leaves taken fromthe pre-harvest dropped fruit trees but none in leaves from the normal fruit trees. There were no differences in soil chemicalproperties between soil samples taken from the normal and pre-harvest dropped fruit trees. It seems likely that greeningdisease is the cause of ‘yellow fruit calyx symptom’ in Thailand and is the resulting from low TNC concentrations, low plantnutrients and low IAA concentrations in the pre-harvest dropped fruits in the pummelo cultivars.

Keywords

• pummelo
• pre-harvest fruit drop
• physiological change
• Thong Dee
• Khao Nam Phueng