Genetic structure of the invasive Colorado potato beetle Leptinotarsa decemlineata populations in China

The Colorado potato beetle(CPB),Leptinotarsa decemlineata Say,is an infamous invasive species worldwide.It was first found in Xinjiang Uygur Autonomous Region of China in 1993 and spread to Northeast China in 2013.To better understand the genetic structure and the diffusion path of their populations in China,we used nine polymorphic microsatellite loci to elucidate the genetic diversity,genetic structure and gene flow among nine CPB populations across Xinjiang and Northeast China.The results show that:(1)Two genetically separated clusters were identified by phylogenetic tree,principal coordinate analysis(PCoA)and Bayesian cluster method.Cluster one contained populations from Xinjiang,China.Cluster two contained populations from Northeast China.A genetic differentiation existed between the two clusters.(2)Three populations in Northeast China hold an obvious genetic differentiation according to the phylogenetic tree and PCoA,indicating that multiple introductions may occur in Northeast China.(3)The Altay population in Xinjiang showed a closer genetic relationship with the populations in Northeast China which may be due to the fact that they collectively originated in neighboring Russia.(4)Among all populations,Mulei and Wusu had obvious gene migrations from Tacheng,indicating that the inland populations are most likely to originate from Tacheng,Xinjiang.

RNA interference in Colorado potato beetle(Leptinotarsa decemlineata): A potential strategy for pest control

Colorado potato beetle(CPB),Leptinotarsa decemlineata,is a notorious destructive pest that mainly feeds on the leaves of potato and several other solanaceous plants.CPB is widely recognized for its adaptation to a remarkable variety of host plants and diverse climates,and its high resistance to insecticides and Bacillus thuringiensis toxins.RNA interference(RNAi)is a sequence-specific,endogenous gene silencing mechanism evoked by small RNA molecules that is used as a robust tool for virus and pest control.RNAi has been extensively tested for CPB management by employing various target genes and delivery methods.This article reviews the screening of RNAi target genes,efficient RNAi delivery systems,and factors affecting RNAi efficiency in CPB,which may help understand the mechanisms of RNAi and its application in CPB control strategy.

Genetic relationships of introduced Colorado potato beetle Leptinotarsa decemlineata populations in Xinjiang, China

The Colorado potato beetle （CPB）, Leptinotarsa decemlineata （Say）, is an infamous invasive species worldwide that aggressively attacks potato and other Solanaceae crops. CPB was first found in China in 1993 and has since spread across 2.77 × 105 km2 in Xinjiang Uygur Autonomous Region. To better understand genetic variation and migration patterns, we used seven polymorphic microsatellite loci to elucidate the genetic relationships and gene flow among 10 CPB populations across Xinjiang. （i） Overall low levels of genetic diversity were detected on the entire population in Xinjiang but most of the diversity was retained among populations during invasion. （ii） The mean pairwise FST was low （0.071 ± 0.043） among populations. The genetic differentiation was little （pairwise FST 0.038 ± 0.016） between the five interior populations （Wusu, Urumqi, Jimsar, Qitai and Mulei） and Tacheng population. The six populations might come from the same genetic group via Bayesian clustering and were closely related on a neighbor-joining tree. Combining the history data, the five interior populations may have originated from Tacheng. （iii） Gene flow was frequent, especially among the five interior populations. Individuals from the interior populations could be assigned to Tacheng at higher probabilities （means 0.518 ± 0.127） than vice versa （means 0.328 ± 0.074）, suggesting that the beetle population has spread from the border to the interior in Xinjiang.

Co-expression of the proteinase inhibitors oryzacystatin I and oryzacystatin II in transgenic potato alters Colorado potato beetle larval development

Colorado potato beetle （CPB; Leptinotarsa decemlineata Say, Coleoptera： Chrysomelidae） has shown a remarkable adaptability to a variety of control measures. Although oryzacystatin I and II （OCI and OCII） have potential in controlling pests that use cysteine proteinases for food digestion, expression of a single OC gene in potato exhibited a minimal or no effect on CPB fitness traits. The aim of this study was to examine the effect of coexpressed OCI and OCII in potato （Solanum tuberosum L.） cultivars Desiree, Draga6evka and Jelica on CPB larvae. Growth parameters, consumption rates and food utilization, as well as activity of proteases of CPB larvae were assayed. Second and third instar larvae fed on transformed leaves molted earlier and had higher relative growth and consumption rates than larvae fed on nontransformed leaves, while efficiency of food utilization was unaffected. In contrast, fourth instar maximum weight gain and amount of leaves consumed were about 20% lower for the larvae fed on transgenic potato. Analysis of total protease activity of third instar larvae revealed reduction in overall proteolytic activity measured by azocasein hydrolysis, accompanied with inhibition ofcysteine proteinase activity 24 h after ingestion of potato leaves expressing OCI and OCII. However, after long-term feeding on transformed leaves proteolytic activities of larvae became similar to the controls. Although feeding on OCI/OCII leaves did not affect larval survival, coexpression of OC genes reduced the development time and thus significantly decreased plant damage caused by CPB larvae.

Adult cannibalism in an oligophagous herbivore, the Colorado potato beetle

Cannibalism, or intraspecific predation, can play a major role in changing individual fitness and population processes. In insects, cannibalism frequently occurs across life stages, with cannibals consuming a smaller or more vulnerable stage. Predation of adult insects on one another is considered to be uncommon. We investigated adult cannibalism in the Colorado potato beetle, Leptinotarsa decemlineata （Say）, which is an oligophagous herbivore specializing on plants in family Solanaceae, and an important agricultural pest. Under laboratory conditions, starvation and crowding encouraged teneral adults to feed upon each other, which reduced their weight loss during the period of starvation. However, pupae were attacked and consumed before adults. Injured beetles had a higher probability of being cannibalized than intact beetles. Males were more frequently attacked than females, but that appeared to be a function of their smaller size rather than other gender-specific traits. Cannibalizing eggs at a larval stage did not affect beetle propensity to cannibalize adults at an adult stage. When given a choice between conspecific adults and mealworrns, the beetles preferred to eat conspecifics. Cannibalistic behavior, including adult cannibalism, could be important for population persistence in this species.

RNA-Based Biocontrols--A New Paradigm in Crop Protection

Modern agribusiness plays a vital role in safeguarding and improving the production,quality,and quantity of food,feed,fiber,and fuel.Growing concerns over the impact of chemical pesticides on health and the environment have stimulated the industry to search for alternative and greener solutions.Over the last years,the RNA interference(RNAi)process has been identified as a very promising new approach to complement the arsenal of foliar spray,soil,or seed treatments applied as chemical and biological pest control agents,and of plant-incorporated protectants(PIPs).RNA-based active ingredients(AIs)possess a unique mode of action and can be implemented via both genetic modification(GM)and biocontrol approaches.RNA-based AIs promise to deliver the selectivity and sustainability desired in future crop protection agents.This is due to their utilization of a natural process to exert control and their high level of selectivity,which leads to reduced risk for non-target organisms(NTOs).This review discusses the advantages and limitations of RNA-based solutions in crop protection and recent research progress toward RNA-based biocontrols against the Colorado potato beetle(CPB),corn rootworm(CRW),and soy stink bug(SSB).Many challenges still exist on the road to the implementation of a broad range of RNA-based products and their widespread use and application.Despite these challenges,it can be expected that RNA-based AIs will become valuable new tools complementing the current arsenal of crop-protection solutions.