LAUSR

ABSTRACT One problem with the pink pulp color of the ‘Thong Dee’ (TD) pummelo (Citrus maxima [Burm.] Merr.) is that it becomes pale during some harvesting periods. The cause of the pale pulp is not known. Therefore, the aim of this study was to determine the effect of growing temperature and rainfall on carotenoid contents and pulp color in the TD fruit. The experiments were conducted in 11 harvesting periods over two years from four orchards. The pale pink pulp coincided with low lycopene and was observed when the average daily minimum temperature two months before harvest was less than 20°C. Lycopene content and a*, which indicates pulp ‘redness’, positively correlated with the average daily minimum temperature two months before harvest (r = 0.6644 and r= 0.6013, respectively). In addition, TD pulp mineral nutrients, which include N, P, K, Ca, Mg, Zn, Cu, Fe, B, Mn, and Na, were not significantly related to the lycopene levels or the pale pink color in the pulp (P> .05). It is possible to conclude that the pale pulp of pummelo fruit is caused by the growing temperature during fruit development. This is the first study that comprehensively addresses the effects of environmental conditions on the pulp color of pummelo fruit. Abbreviations : TD: ‘Thong Dee’; MAP: Months after pollination; ABA: Abscisic acid; GAs: Gibberellic acids; MEP: 2-C-methyl-D-erythritol 4-phosphate; TSS: Total soluble solids; TA: Titratable acidity; HPLC: High performance liquid chromatography; N: Nitrogen; P: Phosphorus; K: Potassium; Ca: Calcium; Mg: Magnesium; Cu: Copper; Zn: Zinc; B: Boron; Fe: Iron; Mn: Manganese; Na: Sodium