QTL MAPPING FOR SIGNIFICANT SEED TRAITS OF WATERMELON (CITRULLUS LANATUS SCHRAD.)

With the ever-increasing demand of healthy vegetable oil for domestic and industrial use, there is the need to seek for alternative sources through molecular breeding to meet this demand. Recently, the Cleaved Amplified Polymorphism Sequence (CAPS) markers were emerged as a powerful source for molecular breeding experiments. Two watermelon accessions named as P-1 = W1-1 (low oil percentage), P-2 = PI-186490 (high oil percentage) and with their F-1 and F-2:3 generation was used for measuring seed oil percentage, also other seed phenotypic traits (seed length, seed thickness, seed width, thickness of seed coat, 100 seed weight). Mean of seed oil percentage (SOP) in PI-186490 (mean = 22.25%) was significantly higher than that of W1-1 (mean = 14.75%). The F2:3 seeds had seed oil percentage ranging from 9% to 32%. Means of other seed traits in P1 and P2 were: seed length (8.81 mm and 14.71 mm), seed width (5.96 mm and 10.53 mm), seed thickness (2.06 mm and 2.65 mm), thickness of seed coat (0.33 mm and 0.15 mm) 100 seed weight (4.70 g and 18.20 g). Overall, 145 CAPS markers with six restriction endonucleases (BamHI, EcoRI, HindII, HindIII, HinfI, PstI) were applied to the F-2 population for molecular genotyping. The linkage map spanned a distance of 3000.19 cM covering the whole genome with an average distance of 20.01 cM. Total of 11 QTLs were detected as follows: seed length (2 QTLs), seed width (1 QTLs), seed thickness (1 QTLs), thickness of seed coat (4 QTLs), 100 seed weight (2 QTLs), seed oil percentage (1 QTLs). QTLs for Seed Length, Seed Width, Thickness of Seed Coat and 100 Seed Weight (qSL-6-1, qSW-6-1, qTSC-6-1, q100SWT-6-1) were all located on chromosome 6 within a less than 5 cM of genetic distance indicating colocalization. The data on seed oil percentage and detected QTLs presented by this study will provide very practical information for future breeding and genetic schemes in watermelon.