Implementation of RNAi-based arthropod pest control : environmental risks, potential for resistance and regulatory considerations

Just over 20 years since the RNA interference (RNAi) mechanism was unraveled in the nematode Caenorhabditis elegans, the first RNAi-based pest control applications are close to commercialization. One of the most alluring aspects of this technology is its predicted minimal impact on the environment, due to high target selectivity and the short persistence of the active molecules in the environment. However, gaps of knowledge on the RNAi mechanism in many species and their implications for biosafety still exist. In this review, we present a comprehensive overview of the research conducted in this field. We discuss potential in planta and topical application methods in the field and their consequences regarding potential exposure in different non-target organisms (NTOs). While RNAi is assumed to be highly species selective, due to its sequence-guided mode of action, dsRNA design will determine how selective a product is. We also discuss molecular and cellular mechanisms affecting RNAi efficacy and how these could become a basis for the emergence of resistance against RNAi-based control products and highlight the need for resistance management. Finally, we briefly discuss recommendations for environmental risk assessment (ERA), such as the value of bioinformatics and the development of properly designed bioassays to predict effects in NTOs or to select NTOs for informing ERA

Genetic diversity and relationships of indigenous and newly bred Bulgarian grape cultivars assessed by nuclear and chloroplast markers

Aim: Assessment of the genetic diversity and relationships in a group of 31 Bulgarian grape accessions through microsatellite markers. Methods and results: Thirty-one accessions, including 20 old rare local and 11 newly bred varieties were characterized through 13 nuclear and 5 chloroplast microsatellite loci. The genetic diversity (0.81±0.01) obtained for the investigated group of cultivars was comparable to those reported for other grapevine germplasms. The low PI value (1.0x10-16) allowed proper genetic identification and determination of synonyms. Microsatellite analysis of the 31 accessions resulted in 26 unique genotypes and 2 groups of synonyms. Four cases of supposed synonymy with local Bulgarian and foreign cultivars were rejected. Three chlorotypes, B, C and D, were defined among the studied cultivars, with a prevalence of chlorotype C (62%). Conclusion: The high genetic diversity found in the set of old rare grapevines demonstrated their importance as a rich source of alleles for breeding. The pattern of chlorotype distribution observed among local varieties confirmed the previous results and supports the hypothesis of an Eastern origin of local Bulgarian cultivars. Significance and impact of the study: The obtained results provide an important support for the preservation of grape biodiversity in Bulgaria as well as for the clarification of genetic relationships between local and foreign cultivars