| The genetic linkage maps were constructed for the Chinese shrimp Fenneropenaeus chinensis using randomly amplified polymorphic (RAPD), amplified fragment length polymorphism (AFLP) and microsatellite makers (SSR) segregating in a F2 family. The F1 family was obtained by crossing a"Yellow Sea No. 1"male with a wild female captured from the west coast of the Korean peninsula. The mapping strategy used in the present study is the pseudo-testcross strategy. Based on these genetic linkage maps, the first report about growth-related QTL mapping in detail was presented in this study.Fifty-two microsatellite loci, 94 RAPD and 4530 AFLP markers were genotyped in the parents and 100 progeny of the mapping family. Among all of the markers, 714 (including 635 AFLP markers, 27 RAPD markers and 52 microsatellite loci) were polymorphic and segregated in one of the parents: 368 in the female and 313 in the male (including part of same micosatellite loci), 50 bands with 3:1 ratio had corresponding bands in both parents. With the sequential Bonferroni correction, the majority of these markers, 295 in the female and 264 in the male, segregated according to the expected 1:1 Mendelian ratio (p≥0.05), total 129 (17.5%) of the polymorphic loci showed significant (P<0.05) segregation distortion. Two genetic linkage maps were constructed using markers segregating in the female or the male parent. The female framework map was composed of 231 markers in 44 linkage groups, covering 2397 cM with an average interval of 7.8 cM. The male framework map contained 204 markers in 44 linkage groups, spanning 2422.5cM with an average marker density of 8.8cM. The distorted markers showing deficient in homozygotes (aa) because the F2 family were all progeny of inbreeding on their full-sib parents (F1) which can give rise to recessive lethal mutations.The map locations and effects of quantitative trait loci (QTL) were estimated for fifteen growth-related characters in Chinese shrimp based on the female and male genetic maps. Except the body length (BL) and the fourth abdominal segment length (A4L), the fifty-nine putatively significant QTL (LOD>2.5) via compositive interval mapping were detected for 13 characters, including 8 QTLs for body weight (BW), 1 QTL for full length (FL), 2 QTLs for carapace length (CL), 5 QTLs for the first abdominal segment length (A1L), 3 QTLs for the second abdominal segment length (A2L), 4 QTLs for the third abdominal segment length (A3L), 13 QTLs for the fifth abdominal segment length (A5L), 2 QTLs for the sixth abdominal segment length (A6L), 4 QTLs for telson length (TL), 3 QTLs for carapace wide (CW), 4 QTLs for the first abdominal segment wide (A1W), 4 QTLs for carapace heigh (CH), 6 QTLs for the first abdominal segment height (A1H). The percentage of phenotypic variation explained by a single QTL ranged from 1.0 to 35.6%.Among all these 59 QTLs, there are 14 major QTLs for 13 traits with the QTLs accounted for 11.5–35.6% of the phenotypic variation. In the female genetic linkage map, 4 major QTLs (STL10.1, A3L1.1, A3L6.2, A5L31.6) located in linkage groups LG10,LG1,LG6 and LG31—were detected for carapace length, the third abdominal segment length and the fifth abdominal segment length with the phenotypic variation 11.5%,13.6%,14.6% and 13.6%, respectively. The other 10 major QTLs of A1L1.1, A1L15.3, A2L1.1,A6L15.1, TL10.1, CW15.2, A1W15.2, CH15.1, CH15.2, A1H15.1 for the first abdominal segment length, the second abdominal segment length, the sixth abdominal segment length, telson length, carapace wide, the first abdominal segment wide, carapace height and the first abdominal segment height were located in male linkage groups. Individually, the QTLs accounted for 12.3–35.6% of the phenotypic variation. The 4 major QTLs, CW2 for carapace wide, CH1 and CH2 for carapace height, A1H1 for the first abdominal segment length, explained 29.8%, 35.6%, 31% and 24.5% of the phenotypic variance, respectively. The 14 QTLs for commerical traits, especially CW15.2, CH15.1, CH15.2 and A1H15.1, may provide a basis for marker-assisted selection to improve productivity in Chinese shrimp breeding. |
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