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Abstract This paper highlights the potential of using polarimetric methods for the inspection of plant diseased tissues. We show how depolarizing observables are a suitable tool for the accurate discrimination between healthy and diseased tissues due to the pathogen infection of plant samples. The analysis is conducted on a set of different plant specimens showing various disease symptoms and infection stages. By means of a complete image Mueller polarimeter, we measure the experimental Mueller matrices of the samples, from which we calculate a set of metrics analyzing the depolarization content of the inspected leaves. From calculated metrics, we demonstrate, in a qualitative and quantitative way, how depolarizing information of vegetal tissues leads to the enhancement of image contrast between healthy and diseased tissues, as well as to the revelation of wounded regions which cannot be detected by means of regular visual inspections. Moreover, we also propose a pseudo-colored image method, based on the depolarizing metrics, capable to further enhance the visual image contrast between healthy and diseased regions in plants. The ability of proposed methods to characterize plant diseases (even at early stages of infection) may be of interest for preventing yield losses due to different plant pathogens.

The authors wish to add the following statement to the Acknowledgments section of article [...]

Polarimetric techniques are widely used in a vast number of applications such as remote sensing, material characterization, astronomy and biological tissue inspection. In this last scenario, different polarimetric observables have proved their potential for enhancing imaging visualization. In this work we use a set of polarimetric observables derived from the arrow decomposition of the Mueller matrix for the first time: enpolarizing, retarding and depolarizing descriptors. In particular, the mean intensity coefficient and the three indices of polarimetric purity, the absolute values and Poincaré orientations of diattenuation, polarizance, entrance retardance and exit retardance vectors are considered. Results show images with enhanced visualization or even revealing invisible structures when compared to standard intensity images. In particular, thanks to these metrics, we improve the visualization of the necrotic areas of a Vitis rupestris leaf. In the case of animal samples, boundaries between different fascicles inside a tendon of an ex vivo chicken sample are revealed, as is the directionality of fiber tracts of the subcortical white matter in an ex vivo cow brain. The experimental results show the potential for biophotonics imaging and how polarimetric techniques could be useful for biomedical and botanical applications.

Red leaf blotch (RLB) of almond, caused by Polystigma amygdalinum, is an important foliar disease of this nut tree in the Mediterranean basin and especially in Spain. In recent years, the control of this disease has become a key factor in the management of Spanish almond orchards. The management of RLB is not easy due to intrinsic factors of the disease (e.g., long infection and latency periods) and the low number of registered fungicides in this country. From 2015 to 2019, different field trials were conducted in the Lleida region, NE Spain, to evaluate the efficacy of several fungicide products and of application strategies to control this disease. Systemic fungicides, which included fluopyram, trifloxystrobin, and mixtures of fluopyram + trifloxystrobin and pyraclostrobin + boscalid, performed better than contact and penetrant products and showed up to 90% control against RLB. However, the efficacy of the tested fungicides varied depending on the year. In terms of application strategies, when fungicide applications were conducted following specific meteorological conditions (after 15 days from >15 mm rainfalls with ≈10–15 °C as the minimum average temperature), their efficacy was comparable to that of calendar-based treatments (every 14, 21, or 31 days from petal fall) but with fewer applications (depending on the year, 2–4 applications as compared with 5–9 for calendar treatments).

Wake-up word spotting in noisy environments is a critical task for an excellent user experience with voice assistants. Unwanted activation of the device is often due to the presence of noises coming from background conversations, TVs, or other domestic appliances. In this work, we propose the use of a speech enhancement convolutional autoencoder, coupled with on-device keyword spotting, aimed at improving the trigger word detection in noisy environments. The end-to-end system learns by optimizing a linear combination of losses: a reconstruction-based loss, both at the log-mel spectrogram and at the waveform level, as well as a specific task loss that accounts for the cross-entropy error reported along the keyword spotting detection. We experiment with several neural network classifiers and report that deeply coupling the speech enhancement together with a wake-up word detector, e.g., by jointly training them, significantly improves the performance in the noisiest conditions. Additionally, we introduce a new publicly available speech database recorded for the Telefónica’s voice assistant, Aura. The OK Aura Wake-up Word Dataset incorporates rich metadata, such as speaker demographics or room conditions, and comprises hard negative examples that were studiously selected to present different levels of phonetic similarity with respect to the trigger words “OK Aura”.

Abstract Several factors contribute to the performance of speaker diarization systems. For instance, the appropriate selection of speech features is one of the key aspects that affect speaker diarization systems. The other factors include the techniques employed to perform both segmentation and clustering. While the static mel frequency cepstral coefficients are the most widely used features in speech-related tasks including speaker diarization, several studies have shown the benefits of augmenting regular speech features with the static ones. In this work, we have proposed and assessed the use of voice-quality features (i.e., jitter, shimmer, and Glottal-to-Noise Excitation ratio) within the framework of speaker diarization. These acoustic attributes are employed together with the state-of-the-art short-term cepstral and long-term prosodic features. Additionally, the use of delta dynamic features is also explored separately both for segmentation and bottom-up clustering sub-tasks. The combination of the different feature sets is carried out at several levels. At the feature level, the long-term speech features are stacked in the same feature vector. At the score level, the short- and long-term speech features are independently modeled and fused at the score likelihood level. Various feature combinations have been applied both for Gaussian mixture modeling and i-vector-based speaker diarization systems. The experiments have been carried out on Augmented Multi-party Interaction meeting corpus. The best result, in terms of diarization error rate, is reported by using i-vector-based cosine-distance clustering together with a signal parameterization consisting of a combination of static cepstral coefficients, delta, voice-quality, and prosodic features. The best result shows about 24% relative diarization error rate improvement compared to the baseline system which is based on Gaussian mixture modeling and short-term static cepstral coefficients.

Two hundred and twenty-five Diaporthe isolates were collected from 2005 to 2019 in almond orchards showing twig cankers and shoot blight symptoms in five different regions across Spain. Multilocus DNA sequence analysis with five loci (ITS, tub, tef-1α, cal and his), allowed the identification of four known Diaporthe species, namely: D. amygdali, D. eres, D. foeniculina and D. phaseolorum. Moreover, a novel phylogenetic species, D. mediterranea, was described. Diaporthe amygdali was the most prevalent species, due to the largest number of isolates (85.3%) obtained from all sampled regions. The second most frequent species was D. foeniculina (10.2%), followed by D. mediterranea (3.6%), D. eres and D. phaseolorum, each with only one isolate. Pathogenicity tests were performed using one-year-old almond twigs cv. Vayro and representative isolates of the different species. Except for D. foeniculina and D. phaseolorum, all Diaporthe species were able to cause lesions significantly different from those developed on the uninoculated controls. Diaporthe mediterranea caused the most severe symptoms. These results confirm D. amygdali as a key pathogen of almonds in Spain. Moreover, the new species, D. mediterranea, should also be considered as a potential important causal agent of twig cankers and shoot blight on this crop.

Grapevine Trunk Diseases (GTDs), particularly esca, are major concerns in Spain. This study characterized the fungal and bacterial communities in a 30-year-old ‘Cabernet Sauvignon’ vineyard in Catalonia, Spain. Six symptomatic vines expressing esca-foliar symptoms and six additional asymptomatic plants were surveyed. Non-necrotic and necrotic tissues were sampled from rootstocks, trunks and cordons of the selected vines. Fungal isolations and molecular techniques were used in combination to investigate the endophytic microflora and to characterize the fungal and bacterial diversity of the vines. Pathogenic fungi involved in GTDs were identified, and the associations were assessed between all the isolated fungal taxa and the health status of vines, host parts and tissue types. Phaeomoniella chlamydospora and Diplodia seriata were found in non-necrotic tissues, whereas Fomitiporia mediterranea was mainly found in soft-rot tissues, and Neofusicoccum parvum and Eutypa cf. lata in hard necrotic tissues. Several Alternaria and Trichoderma species were isolated, mainly from non-necrotic tissues. The single strand conformation polymorphism fingerprinting method showed differences in bacterial and fungal communities between the different types of tissue in healthy and diseased vines. However, no differences were detected in these microbial communities between non-necrotic tissues from asymptomatic and symptomatic vines. Two frequently-isolated species of Paraconiothyrium were tested for pathogenicity, but their pathogenic roles on grapevines was unclear.

Red leaf blotch of almond, caused by the fungus Polystigma amygdalinum, results in early defoliation of trees and decreases fruit production in many Mediterranean and Middle Eastern countries. A latent period of 30–40 d has been reported for this pathogen before disease symptoms are expressed, which makes targeted fungicide control difficult. A quantitative real-time PCR detection method was developed to detect and quantify the fungus in biological samples, to assist early detection. A primer pair was designed based on the ITS region of the fungal rDNA, and this was highly specific and sensitive, enabling detection of a minimum of 12 pg of P. amygdalinum DNA and seven ascospores in artificially-prepared ascospore suspensions. A protocol was also developed to quantify ascospores on plastic tapes which are commonly used in volumetric air samplers. The detection limit for these samples was the same as for ascospore quantification in aqueous suspensions. The pathogen was also quantified in naturally infected leaves showing different stages of disease development, including early stages of leaf infection with doubtful visual identifications. Future practical applications of the method developed here are discussed in view of improving the management of red leaf blotch of almond.

Up to 60 species of fungi in the Botryosphaeriaceae family, genera Cadophora, Cryptovalsa, Cylindrocarpon, Diatrype, Diatrypella, Eutypa, Eutypella, Fomitiporella, Fomitiporia, Inocutis, Phaeoacremonium and Phaeomoniella have been isolated from decline-affected grapevines all around the World. The main grapevine trunk diseases of mature vines are Eutypa dieback, the esca complex and cankers caused by the Botryospheriaceae, while in young vines the main diseases are Petri and black foot diseases. To understand the mechanism of these decline-associated diseases and the symptoms associated with them, the toxins produced by the pathogens involved in these diseases were isolated and characterised chemically and biologically. So far the toxins of only a small number of these decline fungi have been studied. This paper presents an overview of the toxins produced by the most serious of these vine wood pathogens: Eutypa lata, Phaeomoniella chlamydospora, Phaeoacremonium aleophilum and some taxa in the Botryosphaeriaceae family, and examines how these toxins produce decline symptoms. The chemical structure of these metabolites and in some cases their vivotoxin nature are also discussed.

This study assessed the infection rates of different spore inoculum doses of the grapevine trunk pathogens Diplodia seriata, Phaeomoniella chlamydospora and Eutypa lata following artificial inoculation of pruning wounds. Potted vines of cv. Tempranillo were inoculated with doses ranging from 10 to 4000 conidia per wound of D. seriata and P. chlamydospora and led to recovery percentages of 10–100% for D. seriata and 16–94% for P. chlamydospora. Eutypa lata, when inoculated onto wounds of vines in a mature vineyard (cv. Shiraz) and on detached canes (cv. Cabernet Sauvignon) with a dose range of 10 to 1000 ascospores per wound, led to recovery percentages of 17–95%. In the field assay, there was no difference in recovery from wounds that were exposed to single or double inoculations with the same total spore dose, or between canes that were harvested 7 or 11 months after inoculation. The results obtained in this study showed significant variability in pathogen recovery between trials, comparable with that reported previously, which suggests that factors such as pathogen virulence, environmental parameters and experimental conditions may influence the infection process. According to this study, in order to obtain optimal recovery percentages of 50–70% for robust evaluation of pruning wound treatments, dose ranges of 100-1000 conidia of D. seriata, 100–2000 conidia of P. chlamydospora, and 100–500 ascospores of E. lata per wound would be required.

The viability of eight species of Botryosphaeriaceae pathogenic to grapevine was studied after a hot water treatment (HWT) in order to evaluate the feasibility of this technique as a potential tool to control these species during the grapevine propagation process. In a first trial (in vitro), mycelial plugs contained in Eppendorf tubes with sterile distilled water were subjected to different combinations of temperature (50–54°C) and exposure time (15, 30 and 45 min) in a hot water bath. Growth rates of treated mycelia were compared to untreated controls. Significant differences in survival and growth for all factors (species, temperature and time) and their 2-way interactions were observed. Fungal survival and growth generally decreased with increasing temperatures and exposure times. Diplodia seriata, Neofusicoccum luteum, N. parvum and Spencermartinsia viticola were the most susceptible species to temperature, while Lasiodiplodia theobromae and N. vitifusiforme were the most tolerant. In a second trial (in planta), the fungi were inoculated into grapevine canes (Richter 110 rootstock). Inoculated canes were incubated at 25°C for 3 weeks to allow the fungi to colonize the wood and then subjected to HWT in the range of 50–53°C for 30 min, and survival of fungi after HWT was assessed. Survival of all species was sharply reduced after HWT of 30 min at 51°C and higher temperatures. At 50°C, Lasiodiplodia theobromae was the most tolerant species whereas N. luteum was the most susceptible. Results obtained in this study demonstrate the feasibility of controlling these pathogens by HWT in the nursery grapevine propagation process.

The presence and diversity of Diatrypaceae species occurring on grapevines in Eastern Spain were investigated. Several species were identified on the basis of morphological characters and phylogenetic analyses of the complete sequence of the internal transcribed spacers of the ribosomal DNA and part of the β-tubulin gene. Five species of Diatrypaceae isolated from the wood of diseased grapevines, pruning debris and/or perithecia were identified, including Anthostoma decipiens, Cryptovalsa ampelina, Eutypa lata, Eutypella citricola and Eutypella microtheca. Additionally, four taxa could not be identified to the species level but were closely related to Eutypa tetragona based on phylogenetic analyses. Eutypa lata was the most prevalent species and showed the greatest degree of genetic diversity. Cryptovalsa ampelina and E. microtheca ranked second in the frequency of isolations, while all the remaining species were less frequently isolated. Eutypella citricola and E. microtheca are reported for the first time as occurring on grapevine in Spain and this is the first report of A. decipiens occurring on grapevine.

Three independent studies were conducted in Australia and Spain to examine the effect of water and temperature stress on the development of Eutypa dieback of grapevines. In Adelaide, South Australia, ‘Red Grenache’ vines in pots were inoculated with Eutypa lata and subjected to various temperature and soil water regimes, then assessed for foliar symptoms, wood staining and colonization by the fungus. Vines subjected to a combination of heat or cold plus low or high soil moisture displayed more severe foliar symptoms, the most severe occurring on vines subjected to the hottest (30°C) and wettest (20–40 % soil water content) conditions. Wood staining was not related to foliar symptom severity or to the temperature and moisture combination. Furthermore, there was no relationship between staining and mycelial growth, indicating that staining may not be an accurate reflection of the spread of E. lata. In Cabrils, Spain, ‘Tempranillo’ vines were subjected to water stress in pots and showed a significant reduction in shoot diameter growth, stomatal conductance and leaf water potential. Inoculation with E. lata also decreased the leaf water potential of stressed vines. Wood staining in inoculated vines was similar irrespective of watering treatment. Further investigations are needed to elucidate the relationship between stress and growth of E. lata in infected vines. Field experiments in two climatically different regions (Barossa Valley and Riverland) of South Australia suggested that water-stressed vines in a warm, dry environment may be more susceptible to infection of pruning wounds by E. lata than vines receiving standard watering.

Lipophilic phytotoxins produced by Neofusicoccum parvum, a Botryosphaeriaceae species pathogenic to grapevine, were isolated and identified by spectroscopic methods as (3R,4R)-(-)-4-hydroxymellein, (3R,4S)-(-)-4-hydroxymellein, isosclerone and tyrosol. When assayed for phytotoxicity on tomato plants, all four metabolites showed phytotoxic activity, with (3R,4R)-(-)-4-hydroxymellein and isosclerone the most active. Isosclerone is reported for the first time as produced by a Botryosphaeriaceae species