Colorado potato beetle larvae on potato plants expressing a locust proteinase inhibitor.

The natural defence system of plants often involves inhibitors of digestive enzymes of their pests. Modem and environmental-friendly methods try to increase this plant resistance by expressing heterologous protease inhibitors in crops. Here we report the effects of expressing a gene from desert locust (Schistocerca gregaria) encoding two serine protease inhibitors in potato on Colorado potato beetle (Leptinotarsa decemlineata) larvae. The gene encoding both peptides on a single chain was used for Agrobacterium-mediated transformation of potato plants. The presence of the active inhibitor protein in the leaves was verified. The feeding bioassays in the laboratory showed that despite the low level of the peptide in leaves, CPB larvae on transgenic plants have grown slightly but significantly more slowly than those on control potato plants. The results support the notion that expression of multifunctional proteinase inhibitors of insect origin in plants might be a good strategy to improve insect resistance.

Evaluation of genetic diversity of poplar genotypes by RAPD and AP-PCR analysis.

RAPD (randomly amplified polymorphic DNA) and AP-PCR (arbitrarily primed PCR) were utilized to establish the genetic diversity of 19 Populus genotypes. A set of 40 primers of random sequence was tested, of which 35 exhibited polymorphism. Eighteen primers generated 162 easily detectable bands between 250 and 2,500 base pairs in size, sufficient to distinguish between the genotypes. Similarity measures, cluster and multidimensional scaling analysis were performed to evaluate the RAPD and AP-PCR data. Our study demonstrated that in most instances similarity in the RAPD and AP-PCR banding patterns reflected the relationship due to origin. Nineteen primers gave a species or hybrid-specific pattern. One primer generated a specific pattern in P. euramericana. Ten primers produced specific fragments in VIF (P. alba), 4 primers in KOR (P. pyramidialis x P. berolinensis) and 4 primers in UNA and RAS (P. trichocarpa x P. deltoides). The results of this study demonstrated that RAPD or AP-PCR can be used to distinguish between poplar genotypes.