According to the conservative sequence in the epitaxial variable region of Thailand strain of WSSV published in GenBank,a pair of primers were designed to amplify the variable region genes of 5 local WSSV strains(ZHSH,ZHJ,HN,QD1,QD2) by PCR and then cloned.In accordance with the CN,the results indicated that the number of nucleotide of 5 strains were deleted more than 591bp of the TW and TH strains.The ZHSH and HN strains that deleted 591bp at the 3′ end,and 454 bp at the 5′ end of varible gene was highly homologous with CN strain about 99.3%.229bp of ZHJ strain at the 5′ end was homologous with CN about 99.3%,and deleted of 816bp at the 3′ end.97bp at the 5′ end and 171bp at the 3′end of QD1 and QD2 strains were homologous with CN strain about 99.3%,and about 777bp were absent in the middle.The above data showed that the variable region genes of WSSV had mutated more in China.The variable region gene of QD2 strain was coincidence with that of QD1 after propagating 10 generations in crayfish.The results indicated that the crayfish inoculation did not result in mutation of variable region genes of WSSV.
