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International audience; Vole demographics are often modified close to wooded environments. Population monitoring in such settings reveals substantial edge effects, although these have seldom been quantified. This study compares the abundance of common vole Microtus arvalis (Pallas, 1778) populations at various distances from three types of wooded environment (hedgerow, copse and forest) and in two types of habitat (temporary and permanent grassland). In temporary grassland, substantial edge effects were detected along the boundaries of forests and hedgerows. At 100 m from the forest edge, voles were twice more abundant than at 50 m, four times more than at 25 m and eight times more than at 5 m. In permanent grassland, the edge effect was such that voles were practically absent up to 100 m from the forest edge. For both types of grassland, the edge effect was more pronounced for forest habitat than for hedgerows, that is, for elements with a large surface area of wooded environment. Our results suggest that landscape context may greatly affect the local abundance of voles. Given the considerable damage done by M. arvalis, the presence of wooded patches in grassland areas leads to lower vole densities in adjacent areas and this might be an alternative method to control M. arvalis as a pest species.

Plum pox virus (PPV) is the most detrimental virus in stone fruit crops (Prunus sp.). At least nine monophyletic PPV strains are recognized, three of which, PPV-D, PPV-M, and PPV-Rec, have broad distributions (2). PPV-Rec is characterized by a unique founding recombination event and has been reported mostly from Central and South-Central Europe (2). It is generally considered poorly adapted to peach, and the weak and transient symptoms it causes in the GF305 peach seedling indicator may complicate its biological detection (2). During surveys in the Alsace region of France in spring 2013, a plum orchard with trees (Prunus domestica cv. Quetsche d'Alsace 3066) showing dubious leaf symptoms possibly reminiscent of PPV infection was identified. Testing of material from this plant by ELISA (Bioreba AG, Switzerland) gave clear positive reactions, putting the overall infection rate of the orchard at 6.25%, while a second nearby orchard was found infected at a rate of 0.8%. The presence of PPV was confirmed by polymerase chain reaction (PCR) amplification using either the P1-P2 polyvalent primer pair or the P3M-P4b primer pair, which allows the specific amplification of isolates of the Rec and M strains (1). Sequencing of the 467-nt-long P3M-P4b PCR product (Genbank Accession No. KM035763), which spans the end of the NIb gene and the N-terminal hypervariable end of the coat protein gene, provided clear identification of the PPV isolate as belonging to the Rec strain, since it contained all the PPV-Rec specific mutations in the amplified region and showed 98.7 to 97.7% identity with a range of PPV Rec isolates mostly originating from the Balkans. Identification as a PPV-Rec isolate was also confirmed using a strain-specific reverse-transcription–PCR assay (3). This is, to our knowledge, the first report of the presence of PPV-Rec in France. This finding is worrisome given that PPV-Rec is considered well adapted to plum (2), the most important Prunus crop in Alsace. Further surveillance in Alsace during 2014 failed to provide evidence for the presence of PPV-Rec in other areas of the region away from the initial infection focus, which is currently undergoing eradication efforts. References: (1) T. Candresse et al. Phytopathology 88:198, 1998. (2) J. A. García et al. Mol. Plant Pathol. 15:226, 2014. (3) Z. Subr et al. Acta Virol. 48:173, 2004.

National audience; Seedlessness is an important trait in citrus cultivars for the fresh fruit market. It can be obtained by selection of self-incompatibility and sterility genes or by triploid methodology. Auto-incompatibility phenomena induce sterility but cross pollinations restore fertility. INRA and CIRAD-FLHOR are exploring triploid methodology to create new hybrids for diversification of the easy peeler citrus group. One of the possibilities is to select for spontaneous triploids occurring naturally in citrus progenies. These result from gametic cell fusions between a haploid gamete and an unreduced diploid gamete. We crossed three selections of clementine and a mandarin with different citrus species. Considering that the unbalanced level of ploidy between endosperm cells and embryo cells could affect seed development, we screened seeds, and extracted embryos which were then cultivated in vitro. From 99 triploid hybrids, we saved 88 by macro-grafting. We determined the parental origin of diplogamy for 72 triploid hybrids using isozymes. We have found that 2n ovum production (diplogyny) is very frequent, and 2n pollen production (diploandry) is a rare event (less than 2%). A few triploid hybrids have started to fruit. Comparison of seed yield per fruit for triploid hybrids and their genitors showed a dramatic decrease of female fertility leading most of the time to total sterility. Pollen of triploid hybrids was totally sterile.