CAPS marker-base genetic linkage mapping and QTL analysis for watermelon ovary, fruit and seed-related traits

Watermelon possesses diverse ovary, fruit, and seed morphological traits and the successful identification of QTLs/genes controlling these traits are of great significance to breeders. Whole-genome re-sequencing using next-generation sequencing technology was employed to detect SNPs in the parental lines P 1 (ZXG1553) and P 2 (W1-17), for CAPS marker and linkage map development. The linkage map was developed by genotyping of 138 polymorphic CAPS markers with 191-F 2 mapping population that covered all 11 chromosomes with a total length of 1853.34 cM. A total of thirty QTLs (2 Ovary weight, 2 Ovary length, 3 Ovary width, 4 Ovary hairiness, 2 Fruit weight, 1 Fruit length, 1 Fruit width, 1 Brix, 1 Rind thickness, 1 Seed length, 2 Seed width, 4 Rind chlorophyll a, 3 Rind chlorophyll b, and 3 Rind total chlorophyll) were detected for 14 significant ovary, fruit, and seed morphological traits. The QTLs exhibited different LOD score range (2.50 ~ 20.97) and phenotypic explained variance (3.30 ~ 25.91%) for all morphological traits. These detected QTLs and corresponding flanking CAPS markers could be valuable data to facilitate the further investigation in watermelon breeding programs and in-depth genetic basis studies.