Identification of melon fruit quality quantitative trait loci using near-isogenic lines

A collection of melon (Cucumis melo L.) near-isogenic lines (NILs) derived from the cross between the Spanish C. melo cultivar Piel de Sapo (PS) and the exotic Korean accession Shongwan Charmi [SC (PI161375)], was used to study the genetic control of a large number of melon fruit quality traits, including morphological, external appearance, texture, flavor, and the overall differences between NILs and PS that might be detected by consumers with a triangle test. Heritability was significant for all the traits, being >0.5 for the whole area of the longitudinal section of the fruit, flesh proportion, skin lightness color, hue angle coordinate of flesh color, and flesh-extractable juice. NILs were classified by principal-component analysis. The first principal component (22% of the variation) was affected mostly by morphological traits, the second component (10%) was influenced by internal and external morphology pattern and color, and the third component (9%) was controlled mainly by flavor traits. An average of 5.6 quantitative trait loci (QTL) per trait were identified (range, between 1 and 12 QTL; 134 QTL in total). In most cases, allele effects with opposite actions were detected. A substantial number of QTL may be good candidates to introduce new quality attributes in modern melon cultivars.