Breeding Method And Genetic Linkage Maps Construction In Fenneropenaeus Chinensis

The paper presented the appropriate breeding methods and the genetic linkage maps in Fenneropenaeus chinensis. The crossbreeding of F. chinensis and genetic parameters estimates were carried out. The genetic linkage maps were constructed. The results would provide theoretic basis for indirect and early breeding for F. chinensis.1. In order to learn growth characteristics of different geographical populations, intra- and intercrosses of Rushan (WYP) and Korea (WKN) populations were produced. The body length (TL), the carapace length (CL), carapace width (CW), height of the second and third abdominal segment (HST), width of the second and third abdominal segment (WST), body weight (BW) and survival were measured. The heterosis of hybrids was computed, variances were analyzed, and multi-averages were compared. The results indicated that there existed different extent heterosis (4.37%～23.96%) for growth except survival in hybrids at the third month. The offspring of WYP♀×WKN♂had the highest heterosis at the third month, the less was WKN♀×WYP♂, the least was WKN. The effects of morphological trait on body weight of F. chinensis were analyzed in this study.The multiple regression equation describing the body weight is: Y = -2.056 + 0.03X₁ + 0.076X₂ + 0.078X₃ + 0.033X₄ + 0.043X₅.2. At the fourth month, six indexes of growth trait and viability showed a range of heterosis, ranging from 0.514% to 14.950%. The heterosis of WYP♀×WKN♂was higher than that of the WKN♀×WYP♂in all indexes. At the fifth month after post-larvae, six indexes of growth trait and viability ranged from -9.000% to 19.090%. The negative heterosis was observed in CL, HST and viability. The heterosis of WKN♀×WYP♂tended generally to increase as the age of the Chinese shrimp increased while the heterosis of WYP♀×WKN♂tended to decrease. The results indicated that the viability of reciprocal hybrids were not significantly different from their parents. The result of ANOVA indicated that the hybrids were significantly different in WST and BW at the fourth month. The multiple comparisons of LSD test indicated that the hybrids of WYP♀×WKN♂were significantly different from their parents in BW. The hybrids of WYP♀×WKN♂were significantly different from the other three combinations in WST. At the fifth months, the hybrids had significant difference in BW while other traits showed no significant differences from their parents. The multiple comparisons of LSD test indicated that the hybrids of WKN♀×WYP♂were significantly different from the WKN parents in BW.3. The crosses of two wild populations and three farmed populations were produced. The results indicated the survival of JK98 (♀)×WKN (♂) was the highest, followed by WYP (♀)×WKN (♂), WKN (♀)×WYP (♂), FKN (♀)×HH1 (♂) and WYP (♀)×FKN (♂). While the BW of FKN(♀)×HH1(♂) was the highest, followed by WKN (♀)×WYP (♂), WYP (♀)×WKN (♂), WYP (♀)×FKN (♂) and JK98 (♀)×WKN (♂). The TL had the same ranking as the BW. All growth traits in hybrids of JK98 (♀)×WKN (♂) were lowest among all combinations. The hybrids had significant difference in TL, CL, HST, LL and BW. The hybrids were not significant difference in other growth traits and survival rate. The results of Duncan's Multiple Range Test were that the TL and CL of JK98 (♀)×WKN (♂) were significant difference from the other combinations, HST difference from the combination of the WKN (♀)×WYP (♂), FKN(♀)×HH1(♂) and WYP (♀)×WKN (♂) and the BW difference from WKN (♀)×WYP (♂) and FKN(♀)×HH1(♂).4. Twenty-one half-sib groups of the Chinese shrimp were obtained using artificially insemination of two or three females mated each male. Seven growth traits of Chinese shrimp were measured. The heritability was estimated through multiple-trait derivative-free restricted maximum likelihood (MTDFREML). The heritability estimates for all growth traits calculated were significantly different from zero, ranging from 0.15±0.044 to 0.35±0.077. The heritability of TL was 0.34±0.071, CL 0.30±0.070, CW 0.35±0.077, WST 0.33±0.073, HST 0.33±0.073, FL 0.15±0.044 and LL 0.24±0.059, respectively. Genetic correlations were high between growth traits. The genetic correlation between CW and TL was the highest (1.0±0.007), between FL and WST the lowest (0.82±0.085).The crossing scheme and selective breeding indicated the exploitation of heterosis through single crossbreeding in Chinese shrimp was of limiting utility in practical commercial shrimp aquaculture in spite of the potential of significant heterosis. The crossbreeding of different populations can be applied in the establishment of base populations. The systemic selection program based on additive genetic performance may be more effective improvement than crossbreeding.5. The linkage maps were constructed using a F2 population and amplified fragment length polymorphic (AFLP) markers. Fifty-five selected AFLP primer combinations produced 532 AFLP markers in 110 progeny that were fitted for map strategy. From them, the markers in 3:1 segregating ratios were analyzed using F2 intercross model strategy for the common linkage map, the markers in 1:1 ratio using the pseudo-testcross strategy. The separate male and female and common maps for 110 individuals were constructed. The female map included 103 markers which formed 28 linkage groups covering a total length of 1090 cM. In the male map, 144 markers were used to analyzed and grouped to 35 linkage groups covering a total distance of 1617cM, 10 makers unlinked. The common map, 216 markers were used to analyze and group to 44 linkage groups covering a total distance of 1772.1cM, 2 makers unlinked. An average estimated genome size for Chinese shrimp was 2420 cM, which were consistent with the relative size of the penaeid genome compared to the human genome. In Chinese shrimp, the male map was 32.6% larger than the male map, which may reflect sex-specific recombination rates in Chinese shrimp. The distribution of AFLP markers is relatively even in chromosomes of map. The linkage analysis presented in this paper had provided the first insight into the level of polymorphism and genetic variation of Chinese shrimp using AFLP. There has been a further effort to develop additional informative multiplexed microsatellite markers system to establish more saturated linkage map and carry out comparative genomic mapping.