Bovine parainfluenza virus type 3 (BPIV3) is considered as one of the most important respiratory tract pathogens of both young and adult cattle, and widespread among cattle in the world.  BPIV3 was first reported in China in 2008 and four strains of BPIV3 were isolated from Shandong Province, known as genotype C (BPIV3c).  Pathogen investigations had shown that BPIV3c infection was very common among cattle in China.  To date, BPIV3 can be classified into genotypes A, B and C based on genetic and phylogenetic analysis.  Serological survey also demonstrates that BPIV3 infection is widespread in China, however, there is still no available vaccine for BPIV3 prevention in China nowadays.  In the present study, the BPIV3c strain SD0835 was continuously passaged on Madin-Darby bovine kidney (MDBK) cells for hundreds of times, and the pathogenicity of passage 209 was reduced in guinea pigs.  The passage 209 of BPIV3c strain SD0835 was used as a live vaccine candidate to immunize the guinea pigs.  The vaccination results revealed that two vaccinations could induce excellent serum neutralizing antibody responses as well as proliferation of T lymphocytes.  The vaccinated guinea pigs were well protected against challenge with a low passage of BPIV3c strain SD0835.  Additionally, the percentages of CD4⁺ and CD8⁺ T cell subsets of animals in vaccinated group increased after immunization; T cell subsets on day 2 after challenge in both groups decreased, and the decline of CD4⁺ and CD8⁺ T cell subsets levels of four guinea pigs in vaccinated group was relatively moderate, comparing with that of the control group.  These data support further testing of the attenuated virus as an effective candidate vaccine.

    Considering the advantages of single nucleotide polymorphisms (SNP) in genotyping and variety identification, the first set public SNP markers at Cotton Marker Database (http://www.cottonmarker.org/) were validated and screened across standard varieties of cotton distinctness, uniformity and stability (DUS) test, aiming to obtain an appropriate set of core SNP markers suitable for upland cotton cultivars in China. A total of 399 out of 1 005 SNPs from 270 loci including 170 insertions-deletions (InDels) were evaluated for their polymorphisms among 30 standard varieties using Sanger sequencing. As a result, 147 loci were sequenced successfully, 377 SNPs and 49 InDels markers were obtained. Among the 377 SNP markers, 333 markers (88.3%) were polymorphic between Gossypium hirsutum and G. barbadense, while 164 markers (43.5%) were polymorphic within upland cotton. As for InDel markers, the polymorphic rate is relatively lower than that of SNP both between species and within species. The homozygous DNA locus ratio of 121 SNPs was higher than 86.2% while that of other 43 SNPs was less than 70%. Only 64 SNPs displayed completely homozygous genotypes among all of the detected upland cotton varieties with 100% homozygous DNA locus ratio. At last, a set of 23 pairs of core SNPs were achieved in view of avoidance of linkage, with polymorphism information content (PIC) values varying from 0.21 to 0.38 with an average of 0.28. Genotype characteristics and genetic diversity were analyzed based on the set of core markers, while 40 pairs of core simple-sequence repeats (SSR) primers comprised of 10 sets of four multiplex PCR combinations were also used for analysis based on fluorescence detection system. Comparison results indicated that the genetic diversity level was almost equal, while various varieties were significantly different from each other. Genetic relationship revealed by SSR markers is related to geographic source to a certain extent. Meanwhile clustering results analyzed by SNP markers are more consistent with kinship, which demonstrated that the screen strategy for core SNP marker is effective.