Lycopene and Citrulline Contents in Watermelon (Citrullus lanatus) Fruit with Different Ploidy and Changes during Fruit Development

Lycopene and citrulline contents of 9 diploids (2X) and their artificially induced autotetraploids (4X) and autotriploids (3X) were determined in mature fruit. Changes in lycopene and citrulline during fruit development was studied using fruit of variety XYXA with three different ploidy levels from 15 to 40 days after pollination (DAP). Polyploids, especially triploids, had higher levels of lycopene than their diploid progenitors, and triploids tended to contain more lycopene than tetraploids. While levels of citrulline were low and more variable, levels tended to be higher in polyploids than diploids, with triploids tending to be higher than tetraploids. There were only trace amounts of lycopene in fruit of watermelon assayed at 15 DAP, but levels increased rapidly, reaching a maximum value at 37 DAP in tetraploid fruit and 34 DAP in triploid and diploid fruit. The maximum lycopene value of diploid fruit was lower than that of either polyploid fruit. The Lycopene content decreased slightly in over-mature fruit. The maximum citrulline value occurred in fruit that was near maturity. The citrulline content peak was earliest in 2X fruit and was slightly later in 3X and 4X fruit. Changes in citrulline and lycopene in the watermelon fruit followed the same general pattern, being low in young fruit and increasing with fruit size, reaching peak levels at full maturity followed by a slight decrease in over-mature fruit.