Abstract: To map lateral branch associated QTL in melon，a long lateral branch inbred line‘TopMark’and a short lateral branch inbred line‘PI 353814’was crossed to generate a F2 population and F2:3 line in this study. Using a mapping population containing 92 F2 plants and the SSR markers developed from melon genome，a genetic map containing 353 SSR markers was constructed. The total genetic map covered 1 565.88 cM with an average distance between interval markers of 4.44 cM. The genetic length of these linkage groups ranged from 86.98 cM to 186.68 cM. QTL analysis was carried out by combining the phenotypes of lateral branch related traits in F2:3 lines and the genotyping data，and 6 QTLs for these traits were detected on LGⅠ，LGⅢ and LGⅦ，explaining 9.9242% ~ 48.2348% of total phenotypic variation.Among them，two major QTL lbtl7.1 and lbal7.1 were mapped on chromosome LGVⅡ between markers CmSSR17145 and CmSSR17293，explaining 38.5923% and 48.2348% of the phenotypic variation，respectively. In order to validate these major QTLs，new SSR markers were developed in the candidate region，and an extended population of 186 F2:3 lines were used for QTL mapping. The results showed that the major QTL lbtl7.1 was further mapped between CmSSR17251 and CmSSR17253 markers with a genetic distance of 2.5 cM and 0.5 cM，explaining 41.2742% of the phenotypic variation. Another major QTL lbal7.1 was further mapped between CmSSR17238 and CmSSR17251，with a genetic distance of 1.5 cM and 0.5 cM，respectively，explaining 55.1739% phenotypic variation.

Key words: melon, lateral branch, F2:3, genetic map, QTL mapping