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ISSR was applied to detect the relationship between 16 Cymbidium species, and 836 bands were amplified with 15 primers, including 227 polymorphic bands. The polymorphic percentage is 27.2%. UPGMA results showed that the genetic distance were closest between C.goeringii (Rchb.f.) Rchb.f. and C. goeringii var. longibracteatum, and C.lancifolium Hook. was far away from the other 15 species. This result is quite similar to the traditional classification, indicating that the technique could supplement some information to traditional taxonomy in the molecular level.

A sacB mutant was obtained by transposon IS10 inactivation of a plasmid pXT3sacB carrying the sacB gene. Sequencing of this mutant plasmid DNA (GenBank accession No. AY580883.1) showed that the IS10 flanking the 22 bp inverted repeats were 5'-CTGAGAGATCCCCTCATAATTT-3' and 5'-AAATCATTAGGGGATTCATCAG-3', which were the similar to those published in reports previously. However, the target sequence adjacent to IS10 was 5'-TGCTTGGTT-3' instead of the previously reported 5'-NGCTNAGCN-3'. To our knowledge, this is the first report on the novel insertion site of IS10. In addition, Southern blot hybridization confirmed that the mobile IS10 originated from the chromosomal DNA of the host strain Escherichia coli DH5alpha and that there were two copies in the DH5alpha genome.

The presence in transgenic plants of antibiotic and herbicide resistant selective marker genes might be an unpredictable hazard to the ecosystem as well as to human health. There are two applicable strategies can be used to resolve this problem. One is to remove the resistant marker genes before the transgenic plants are released to field. The other is to develop and use safe marker genes to produce transgenic plants. The present paper reviewed three technique systems employed to remove resistant marker genes in transgenic plants and several safe marker genes used in plant transformation.

Virus disease is a major cause that affects the quality and output of watermelon which is an important fruit in summer. So it is really urgent to develop disease resistance plants. But it takes a long time to breed such plants in conventional ways, and it is very difficult to get ideal result. With the development of plant genetic engineering, new ways have been found to breed plants with disease resistance. By using plant transgenic technique, much progress was been made in plant improvement. There are many successful cases of transgenic plants against corresponding virus disease through transferring coat protein gene. This paper reports the results of inheritance, segregation, expression of WMV-2 coat protein gene in inbred transgenic watermelon and its resistance to virus. Through PCR analysis of inbred plants, we found WMV-2 coat protein gene in the genome of progeny R1 separated with 3:1. After successive selection and identification of 4 generations, 8 transgenic pure lines with almost the same agronomic traits were obtained from 3 independent transformants of T7, T11 and T32. The result of Western blotting shows all 3 different transgenic lines of R4T7-1, R4T11-3 and R4T32-7 can produce coat protein. Disease resistance experiment on transgenic plants with WMV-2 shows that, compared with the control groups, transgenic plants can delay the disease infection and reduce the incidence and the symptoms of virus disease. And the transgenic line R4T32-7 expressed high resistance to infection by WMV-2, which lays a foundation for breeding of disease resistant varieties through plant transgenic technique.