The random amplified polymorphic DNA(RAPD) technique and the morphological variation analysis were used to evaluate population genetics among three wild populations of clam Lutraria siebaldii in coastal Guangxi and Guangdong provinces and one population Lutraria maxima in coastal Vietnam.A total of 428 scorable markers were amplified from 20 RAPD primers in 145 samples from different populations of Lutraria siebaldii and Lutraria maxima,ranging from 125 to 5 000 bp in size,and the number of the scorable bands for each primer varied from 6 to 17,with the average polymorphic band proportion of 84.5%.The mean percent of polymorphic loci in four populations were ranged from 76.1% to 91.9% with genetic distance from 0.1321 to 0.2441 among individuals.The cluster analysis according to their genetic distances,first Zhanjiang,Beihai and Fangcheng populations,and then with Vietnam population,revealed that the 3 wild populations of Lutraria siebaldii were distinguished by 8 primers.The morphological variations showed that the samples from Zhanjiang,Beihai and Fangcheng populations were rather similar in morphology,whereas Vietnam population differed greatly from the other populations in morphology,indicating that these clams were divided into different species.In the principal component analysis,the contributory ratio of the three principal components was 49.13%,17.18% and 14.02%,respectively,and the cumulative contributory ratio was 80.33%.The discrimination functions of the four populations were set up,the discrimination accuracy being 88.9%~100.0% for P1 and 86.7%~ 100.0% for P2,the integrative discrimination accuracy being 95.9%.The resource of Lutraria siebaldii was found in good condition with high genetic variation and Lutraria siebaldii had good culture prospects.

Nineteen RAPD primers amplified a total of 182 scorable markers in 200 samples from the four different natural populations of H.tuba,thus a total of 19 983 bands which ranged in size from 250 to 2 500 bp were generated showing homogeneous RAPD patterns,and number of scorable bands for each primer varied from 4 to 17 with an average of 5.28 bands per RAPD primer.81.87% of the total genetic diversity was found among the four populations which contained approximately 149 polymorphic loci.66.48%,47.25%,44.51%,36.81% of the total genetic diversity were attributable to genetic differences within Beihai,Zhanjiang,Wenzhou,Lianyungang populations.Estimates of Nei’s Gene Diversity and the Shannon’s Diversity Index provided similar results of diversity,from high to low,that is,Beihai,Zhanjiang,Wenzhou,Lianyungang populations.The cluster analysis of the four populations was based on Genetic Distance,which was measured between 0.054 2-0.137 4.The results showed the populations of Beihai and Zhanjiang first assembled one branch,Wenzhou and Lianyungang then assembled another,and the two branches assembled finally.

The radula of Hemifusus tuba(Gmelin),Hemifusus colosseus(Lamarck),and Hemifusus kawamurai Habe were morphologically compared in this article.The samples of the three species had 10 populations from different coastal regions of China and each population has 10―20 individuals.The results show that there are always three teeth of each row symmetri-cally arrayed in the radula of Hemifusus,and the pattern of radula is 1·1·1.Different species in Hemifusus have little disparity,and the main discrepancy is in the central protruding of the central teeth.Different populations in H.tuba have no apparent difference.The discrepancy between species is a litte larger than that in the same species.Populations of H.tuba have apparent difference with H.colosseus and H.kawamurai Habe(P0.05).Populations of H.colosseus have no apparent difference with H.kawamurai.The ratio of the length of 1st protruding of the lateral teeth /the width of the central teeth in the populations of H.colosseus from the Beibu Bay have apparent difference with H.kawamurai from the Yangjiang(P0.01).Different popula-tions in Hemifusus have little difference in radula,which is related to the coincident life habit.It is suggested that the radula parameter could not be used in indentifying different populations in H.tuba.

250 birds with tumors collected from Nanning, Yulin, Guilin, Qinzhou, Liuzhou, Wuzhou during the years of 2000 to 2003 were detected for exogenous avian leukosis virus (ALV) and Marek's disease virus (MDV-1) by a tumors detection kit developed in the laboratory. The results show that 32 (12.8 %) birds were positive of exogenous ALVs, in which 30 (93.75 %) birds were also positive of virulent MDV-1. 20 samples of the exogenous ALVs were randomly used for the sub-grouping by RFLP(restriction fragment length polymorphism)analysis of the glycoprotein gene gp85 of the viral genomes, and the results show that they are all belong to subgroup A.

1 概况 肉鸡传染性发育迟缓综合征(infectious stunting syndrome,ISS)因临床上的表现不同,在不同的文献中有众多的名称,如鸡生长受阻和发育障碍综合征(runting stunting syndrome, RSS)、直升机羽病、苍白综合征、骨质疏松症、脆骨病、股骨头坏死、传染性腺胃炎等,是一种主要侵害快速生长幼龄肉鸡(尤其是肉用种鸡)肠道的多征候性(multi-symptomatic)疾病.

sets of PCR primers were designed to amplify specific DNA fragment from the genomes of APMV- 1 ,DPV and GPV respectively for the diagnosis of the most common viral diseases in geese.The specific PCR productswere amplified by the corresponding primersfrom the reference strainsof each virus, but not from other pathogens;38field samples from different areas of Guangxi were detected with the developed PCR- based diagnosis protocol and 66. 6% ,5 5 . 6% and 75 % of the detected samples were positive for DPV,APMV- 1 and GPV respectively,and totally 42 . 8% ( 9/ 2 1 ) for the dual and triple infections.The results demonstrated that developed PCR- based protocols is a rapid,sensitive,specific and reliable for the diagnosis of these diseases in geese and can be applied in the field especially for the multiple infections and the epidemiological survey.