Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/17/2003
Publication Date: 9/9/2003
Citation: Beaulieu, J.C., Peralta-Inga, Z., Lea, J.M., Eggleston, G. 2003. Sugar and organic acid variations in commercial cantaloupes and their inbred parents. Journal of the American Society for Horticultural Science. 1284:531-536. Interpretive Summary: Consumer acceptance of melons is driven most often by sweetness and also by an acceptable aroma bouquet or presence of flavor compounds. However, the most common measurement of quality, sugars, is only partially related with sweetness, and high sugar content alone does not appear to adequately define "good melon quality." Melon quality deteriorates rapidly after harvest or fresh-cutting. Subsequently, breeding companies are attempting to find breeding tools called markers; compounds associated with desirable flavor and maintained quality after harvest. This study was performed to analyze simple sugars and acids in two commercially available cantaloupe varieties and their inbred male and female parental lines to determine if differences in quality parameters could be related with parental lineage or melon type/growing region. Results indicate that maternal inheritance appears to control higher pH and lower sugar accumulating capacity in the melon lines tested. Breeding programs might need to focus on utilizing female lines with lower pH and higher sugar contents to improve overall cantaloupe quality. Improved varieties should enhance the retailer's and fresh-cut producer's ability to deliver consistent, consumer-accepted, highly demanded cantaloupe products to the market. This will benefit the seed industry, farmers and fresh-cut companies who provide, grow and process melons.
Technical Abstract: Higher average sucrose was recovered from mesocarp tissue of six orange-flesh cantaloupe varieties over three seasons compared to glucose and fructose. A decrease in sucrose concentration was observed in the fall for all 6 varieties, and the glucose and fructose ratios were also higher in the fall; different from the spring fruit averages. Female lines had lower glucose, fructose, sucrose and total sugars than the commercial lines. Compared to male and female inbred lines, commercial varieties had higher concentrations of fructose, sucrose and total sugars, but not glucose. Two refractometric digital measures of °Brix in homogenized slurries were positively correlated, and were also correlated with total sugars and sucrose. °Brix of cubes was correlated with sucrose and total sugars. Total sugar was positively correlated with sucrose. Eastern melons had higher °Brix-cube and °Brix-At compared to western shippers. Female lines were lower in mean °Brix compared to the commercial and male lines, and female lines had higher pH's than male lines. Western shippers had higher pH's compared to eastern varieties. Predominant organic acid in all six varieties was succinic acid, followed by oxalic, citric/isocitric, then malic acid. Succinic acid recovery was higher in all six varieties harvested in the fall, compared to spring. Eastern varieties had lower organic acids compared to western varieties. Results indicate that maternal inheritance appear to confer higher pH, which is associated with vacuolar acid invertase and hexose balance, and lower sugar accumulating capacity. Breeding programs should focus on utilizing homozygous female lines with lower pH and higher sugar contents.