Genetic Analysis Of Four Generations Selected On Disease-Resistance Trait And Construction Of Genetic Linkage Map Of Fenneropenaeus Chinensis Based On AFLP Markers

Stable and reliable reaction conditions of AFLP analysis in Fenneropenaeus chinensis were established after optimizing PCR factors which had an effect on AFLP fingerprinting. AFLP was used to analyze the genetic structure of four generations successively selected on disease-resistant traits of F.chinensis. Data showed low genetic diversity of F. chinensis and difference between the levels of genetic variation in the four generations. The genetic structure has changed due to artificial selection and genetic differentiation index indicated slight differentiation among them. Our results indicated there was great potential for selective breeding. In AFLP fingerprinting, some loci showed quite different frequency in four generations and they were assumed as putative markers closely related to disease-resistant trait. These fragment were recovered, cloned and sequenced, and a BLAST analysis was made. Co-dominant loci was found in AFLP markers, showing AFLP markers was not purely dominant. We compared the difference between genetic parameters derived from several statistical methods, including AMOVA, Nei and Shannon diversity analyses. We recommended AMOVA the first choice in analysis of population genetics with AFLP technique.Genetic linkage maps of F.chinensis have been constructed using "two-way pseudo-testcross" strategy with AFLP markers. Parents and Fl progeny (full sib family) was used as segregating population. Together 135 and 118 markers fitted to Mendelian segregation ration for paternal and maternal parent was produced from 34 AFLP primer combinations. In the linkage map of paternal parent, 74 markers distributed in'25 linkage groups, which covered a total length of 951.5cM. The longest and shortest linkage group was 206.2 cM and 7.4cM respectively. The maternal linkage map consisted of 66 marker loci in 22 groups, which cover the map distance about 712.7 cM. The size of the linkage groups ranged from 7.7 to 128.2 cM.The average resolution of the paternal and maternal parent was 12.8 and 10.7 cM, respectively. The estimated genome length of F.chinensis is about 2000 cM, so the map covered the 47.5% and 35.6% of the genome.The map with moderate density developed here provides a first step in producing a saturated linkage map of F.chinensis and open the way for marker assisted selection, comparative genomics and gene location and clone.