Intron-Containing Hairpin RNA Interference Vector for OBP8 Show Promising Mortality in Peach Potato Aphid

Myzus persicae is a devastating pest affecting potato production. RNA Interference technology is used against essential odorant binding protein 8 (OBP8) to enhance protection against Myzus persicae in potato. Gene was isolated, sequenced and GenBank IDs were allotted and ERNAi was used to design siRNA targets from OBP8 with no off-targets. Multiple Sequence Alignment show M. persicae OBP8 resemblance with Acyrthosiphon pisum, Rhopalosiphum maidis, Aphis fabae, and Sitobion avenae. DsRNA (7 µg/µl) oral acquisition had resulted in 69% mortality and 58% reduction in OBP8 expression 8D post dsRNA feeding in comparison to control. Golden Gate (GG) cloning based RNAigg is used for RNA interference taking advantage of type IIs restriction enzyme Eco31I. Agro infiltration assay was used for introduction of intron-containing hairpin RNA (ihpRNA) in Solanum tuberosum. Aphids feeding on transgenic S. tuberosum show 57.6% mortality and 49% reduction in OBP8 expression 8d post-feeding in comparison to control. This work proves OBP8 as promising ihpRNA targets in potato and related crops for whom Myzus is a devastating target.

Repellent and Antifeedant Activities of Citral-Derived Lactones against the Peach Potato Aphid

Citral is well known for its antimicrobial, antifungal, and insecticidal activities. Natural sesquiterpene α-methylenelactones also exhibit a broad spectrum of biological activities. The aim of the study was to explore the effect of structural changes to citral molecules on citral behavior-modifying activity towards Myzus persicae. Specifically, the effects of the introduction of a γ-lactone moiety and methylene groups in α and γ positions of the lactone ring were investigated. The lactones were obtained in five-step (saturated lactone and γ-methylenelactone) or six-step (α-methylenelactone and α,γ-dimethylenelactone) syntheses from citral. The synthetic procedures and physical and spectral data of the lactones are presented. The settling behavior of freely moving aphids in choice and no-choice situations was monitored. The probing behavior of tethered M. persicae using the Electrical Penetration Graph (EPG) technique was also analyzed. Citral appeared a strong repellent and pre-ingestive and ingestive probing deterrent to M. persicae. The incorporation of a lactone moiety caused the loss of the repellent activity. α-Methylenelactone inhibited aphid settling and probing activities at pre-ingestive and ingestive phases. The saturated γ-lactone and α,γ-dimethylenelactone were the settling post-ingestive deterrents to M. persicae, which did not affect aphid probing activity. γ-Methylenelactone did not affect aphid behavior.

Susceptibility of Myzus persicae, Brevicoryne brassicae and Nasonovia ribisnigri to Fungal Biopesticides in Laboratory and Field Experiments

The aim of this study was to evaluate the potential of entomopathogenic fungi (EPF) for the control of aphid pests of field vegetable crops. Four biopesticides based on the EPF Beauveria bassiana (Botanigard ES and Naturalis L), Cordyceps fumosorosea s.l. (Preferal WG), and Akanthomyces dipterigenus (Vertalec) were evaluated in a laboratory bioassay against peach-potato aphid Myzus persicae, cabbage aphid Brevicoryne brassicae, and currant-lettuce aphid Nasonovia ribisnigri. There was significant variation in the spore dose provided by the products, with Botanigard ES producing the highest dose (639 viable spores per mm2). Botanigard ES also caused more mortality than the other products. Combining Vertalec with the vegetable oil-based adjuvant Addit had an additive effect on the mortality of B. brassicae. All fungal products reduced the number of progeny produced by M. persicae but there was no effect with B. brassicae or N. ribisnigri. When aphid nymphs were treated with Botanigard ES and Preferal WG, both products reduced population development, with up to 86% reduction occurring for Botanigard ES against M. persicae. In a field experiment, Botanigard ES sprayed twice, at seven-day intervals, against B. brassicae on cabbage plants, reduced aphid numbers by 73%. In a second field experiment with B. brassicae, M. persicae, and N. ribisnigri, Botanigard ES reduced populations of B. brassicae and N. ribisnigri but there was no significant effect on M. persicae.

Identification and QTL mapping of resistance to Turnip yellows virus (TuYV) in oilseed rape, Brassica napus

Key message Partially dominant resistance to Turnip yellows virus associated with one major QTL was identified in the natural allotetraploid oilseed rape cultivar Yudal. Abstract Turnip yellows virus (TuYV) is transmitted by the peach-potato aphid (Myzus persicae) and causes severe yield losses in commercial oilseed rape crops (Brassica napus). There is currently only one genetic resource for resistance to TuYV available in brassica, which was identified in the re-synthesised B. napus line ‘R54’. In our study, 27 mostly homozygous B. napus accessions, either doubled-haploid (DH) or inbred lines, representing a diverse subset of the B. napus genepool, were screened for TuYV resistance/susceptibility. Partial resistance to TuYV was identified in the Korean spring oilseed rape, B. napus variety Yudal, whilst the dwarf French winter oilseed rape line Darmor-bzh was susceptible. QTL mapping using the established Darmor-bzh × Yudal DH mapping population (DYDH) revealed one major QTL explaining 36% and 18% of the phenotypic variation in two independent experiments. A DYDH line was crossed to Yudal, and reciprocal backcross (BC1) populations from the F1 with either the susceptible or resistant parent revealed the dominant inheritance of the TuYV resistance. The QTL on ChrA04 was verified in the segregating BC1 population. A second minor QTL on ChrC05 was identified in one of the two DYDH experiments, and it was not observed in the BC1 population. The TuYV resistance QTL in ‘R54’ is within the QTL interval on Chr A04 of Yudal; however, the markers co-segregating with the ‘R54’ resistance are not conserved in Yudal, suggesting an independent origin of the TuYV resistances. This is the first report of the QTL mapping of TuYV resistance in natural B. napus.

Comparative Analysis of Intra- and Inter-Specific Genomic Variability in the Peach Potato Aphid, Myzus persicae

The availability of genomic data in the last decade relating to different aphid species has allowed the analysis of the genomic variability occurring among such species, whereas intra-specific variability has hitherto very largely been neglected. In order to analyse the intra-genomic variability in the peach potato aphid, Myzus persicae, comparative analyses were performed revealing several clone-specific gene duplications, together with numerous deletions/rearrangements. Our comparative approach also allowed us to evaluate the synteny existing between the two M. persicae clones tested and between the peach potato aphid and the pea aphid, Acyrthosiphon pisum. Even if part of the observed rearrangements are related to a low quality of some assembled contigs and/or to the high number of contigs present in these aphid genomes, our evidence reveals that aphid clones are genetically more different than expected. These results suggest that the choice of performing genomes sequencing combining different biotypes/populations, as revealed in the case of the soybean aphid, Aphis glycines, is unlikely to be very informative in aphids. Interestingly, it is possible that the holocentric nature of aphid chromosomes favours genome rearrangements that can be successively inherited transgenerationally via the aphid’s apomictic (parthenogenetic) mode of reproduction. Lastly, we evaluated the structure of the cluster of genes coding for the five histones (H1, H2A, H2B, H3 and H4) in order to better understand the quality of the two M. persicae genomes and thereby to improve our knowledge of this functionally important gene family.