Fire blight is the most important bacterial disease in apple (Malus×domestica) and pear (Pyrus communis) production. Today, the causal bacterium Erwinia amylovora is present in many apple-and pear-growing areas. We investigated the natural resistance of the wild apple Malus×robusta 5 against E. amylovora, previously mapped to linkage group 3. With a fine-mapping approach on a population of 2,133 individuals followed by phenotyping of the recombinants from the region of interest, we developed flanking markers useful for marker-assisted selection. Open reading frames were predicted on the sequence of a BAC spanning the resistance locus. One open reading frame coded for a protein belonging to the NBS-LRR family. The in silico investigation of the structure of the candidate resistance gene against fire blight of M.×robusta 5, FB_MR5, led us hypothesize the presence of a coiled-coil region followed by an NBS and an LRR-like structure with the consensus 'LxxLx[IL]xxCxxLxxL'. The function of FB_MR5 was predicted in agreement with the decoy/guard model, that FB_MR5 monitors the transcribed RIN4_MR5, a homolog of RIN4 of Arabidopsis thaliana that could interact with the previously described effector AvrRpt2 EA of E. amylovora.

SummaryThe fire blight susceptible apple cultivar Malus 9 domestica Borkh. cv. 'Gala' was transformed with the candidate fire blight resistance gene FB_MR5 originating from the crab apple accession Malus 9 robusta 5 (Mr5). A total of five different transgenic lines were obtained. All transgenic lines were shown to be stably transformed and originate from different transgenic events. The transgenic lines express the FB_MR5 either driven by the constitutive CaMV 35S promoter and the ocs terminator or by its native promoter and terminator sequences. Phenotyping experiments were performed with Mr5-virulent and Mr5-avirulent strains of Erwinia amylovora, the causal agent of fire blight. Significantly less disease symptoms were detected on transgenic lines after inoculation with two different Mr5-avirulent E. amylovora strains, while significantly more shoot necrosis was observed after inoculation with the Mr5-virulent mutant strain ZYRKD3_1. The results of these experiments demonstrated the ability of a single gene isolated from the native gene pool of apple to protect a susceptible cultivar from fire blight. Furthermore, this gene is confirmed to be the resistance determinant of Mr5 as the transformed lines undergo the same gene-for-gene interaction in the host-pathogen relationship Mr5-E. amylovora.

BACKGROUND The fruit fly Drosophila suzukii , or spotted wing drosophila (SWD), is a serious pest worldwide, attacking many soft‐skinned fruits. An efficient monitoring system that identifies and counts SWD in crops and their surroundings is therefore essential for integrated pest management (IPM) strategies. Existing methods, such as catching flies in liquid bait traps and counting them manually, are costly, time‐consuming and labour‐intensive. To overcome these limitations, we studied insect trap monitoring using image‐based object detection with deep learning. RESULTS Based on an image database with 4753 annotated SWD flies, we trained a ResNet‐18‐based deep convolutional neural network to detect and count SWD, including sex prediction and discrimination. The results show that SWD can be detected with an area under the precision recall curve (AUC) of 0.506 (female) and 0.603 (male) in digital images taken from a static position. For images collected using an unmanned aerial vehicle (UAV), the algorithm detected SWD individuals with an AUC of 0.086 (female) and 0.284 (male). The lower AUC for the aerial imagery was due to lower image quality caused by stabilisation manoeuvres of the UAV during image collection. CONCLUSION Our results indicate that it is possible to monitor SWD using deep learning and object detection. Moreover, the results demonstrate the potential of UAVs to monitor insect traps, which could be valuable in the development of autonomous insect monitoring systems and IPM. © 2020 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Microbial infections in plant leaves remain a major challenge in agriculture. Hence an understanding of disease mechanisms at the molecular level is of paramount importance for identifying possible intervention points for their control. Whole-transcriptome changes during early disease stages in susceptible plant species are less well-documented than those of resistant ones. This study focuses on the differential transcriptional changes at 24 hours post inoculation (hpi) in tomato leaflets affected by three pathogens: (1) Phytophthora infestans, (2) Botrytis cinerea, and (3) Oidium neolycopersici. Grey mould (B. cinerea) was the disease that had progressed the most by 24 hpi, both in terms of visible symptoms as well as differential gene expression. By means of RNA-seq, we identified 50 differentially expressed tomato genes specifically induced by B. cinerea infection and 18 specifically induced by P. infestans infection at 24 hpi. Additionally, a set of 63 genes were differentially expressed during all three diseases when compared by a Bayesian approach to their respective mock infections. And Gene expression patterns were found to also depend on the inoculation technique. These findings suggest a specific and distinct transcriptional response in plant leaf tissue in reaction to B. cinerea and P. infestans invasion at 24 hpi, indicating that plants may recognize the attacking pathogen.

Recent observations report the worldwide incidence of leaf-feeding grape phylloxera in formerly resistant scions of commercial vineyards. To analyze the genetic structure of leaf-feeding phylloxera, we performed an extensive sampling of leaf-feeding phylloxera populations in seven regions (Bcantons^) in Switzerland and Germany. The use of polymorphic microsatellite markers revealed presence of 203 unique grape phylloxera multilocus genotypes. Genetic structure analyses showed a high genetic similitude of these European samples with phylloxera samples from its native habitat on Vitis riparia (northeastern America). Nevertheless, no genetic structure within the European samples was observed, and neither host, geography nor sampling date factors caused clear effects on phylloxera genetic stratification. Clonality was high in commercial vineyards and leaf-feeding grape phylloxera strains were found to be present in scion leaves and rootstock roots in the same vineyard, potentially indicating migration between both habitats. We found indications of sexual reproduction, as shown by high degrees of genetic variation among collection sites.