Application of artificial neural networks to classify Avena fatua and Avena sterilis based on seed traits: insights from European Avena populations primarily from the Balkan Region.

BACKGROUND: Avena fatua and A. sterilis are challenging to distinguish due to their strong similarities. However, Artificial Neural Networks (ANN) can effectively extract patterns and identify these species. We measured seed traits of Avena species from 122 locations across the Balkans and from some populations from southern, western, and central Europe (total over 22 000 seeds). The inputs for the ANN model included seed mass, size, color, hairiness, and placement of the awn attachment on the lemma. RESULTS: The ANN model achieved high classification accuracy for A. fatua and A. sterilis (R2 > 0.99, RASE < 0.0003) with no misclassification. Incorporating geographic coordinates as inputs also resulted in successful classification (R2 > 0.99, RASE < 0.000001) with no misclassification. This highlights the significant influence of geographic coordinates on the occurrence of Avena species. The models revealed hidden relationships between morphological traits that are not easily detectable through traditional statistical methods. For example, seed color can be partially predicted by other seed traits combined with geographic coordinates. When comparing the two species, A. fatua predominantly had the lemma attachment point in the upper half, while A. sterilis had it in the lower half. A. sterilis exhibited slightly longer seeds and hairs than A. fatua, while seed hairiness and mass were similar in both species. A. fatua populations primarily had brown, light brown, and black colors, while A. sterilis populations had black, brown, and yellow colors. CONCLUSIONS: Distinguishing A. fatua from A. sterilis based solely on individual characteristics is challenging due to their shared traits and considerable variability of traits within each species. However, it is possible to classify these species by combining multiple seed traits. This approach also has significant potential for exploring relationships among different traits that are typically difficult to assess using conventional methods.

First report of Colletotrichum fioriniae causing anthracnose on pear fruit in Serbia.

European pear (Pyrus communis L.) is one of the most important fruits in Serbia, with a total production of 55,938 tonnes in 2021 (Statistical Office of the Republic of Serbia). In November 2021, pear fruits (cv. Santa Maria) with typical anthracnose symptoms were collected in one storage facility in the area of Smederevo, Serbia. The disease incidence was about 2%. A total of nine infected fruits had dark, circular, sunken necrotic lesions with concentric rings of orange conidial masses produced in black acervuli. The tissue pieces from the edges of lesions (3 to 5 mm2) were surface-sterilized in 1% sodium hypochlorite for 1 min, rinsed twice in sterilized distilled water, air-dried, and incubated on potato dextrose agar (PDA) at 25°C. One isolate/diseased fruit was obtained (nine in total). Colony morphology of all isolates on PDA was light gray to pinkish on the upper side, and pink to vinaceous on reverse after 7 days of incubation at 25°C in the dark. Average growth rate was 64 ± 2 mm. The conidia were hyaline, fusiform, aseptate, smooth-walled, with both ends acute, and measured 12.8 to 16.6 µm × 3.5 to 4.5 µm (n =100). Appressoria were single, smooth-walled, dark brown, clavate to irregular outline, 5.5 to 9.6 × 4.8 to 7.2 µm (n =20). These morphological characterstics are consistent with the description of Damm et al. (2012) for Colletotrichum fioriniae. To confirm this identification, genomic DNA of representative isolate SZ-21-36 was extracted and the ITS region of the rDNA, partial beta-tubulin gene (BenA), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and partial actin gene (ACT) were amplified using the primers ITS1/ITS4, Bt2a/Bt2b, GDF1/GDR1, and ACT512F/ACT783R, respectively (Hassan et al. 2019). The nucleotide sequence of each locus has been deposited in GenBank under Accession Nos. ON171625 (ITS), ON186696 (BenA), ON186697 (GAPDH), and ON186698 (ACT). Multilocus phylogenetic analysis based on the above mentioned molecular markers placed Serbian isolate of C. fioriniae with other isolates of this species deposited in GenBank (bootstrap support of 100%). Pathogenicity test was conducted on symptomless, detached pear fruits (cv. Santa Maria). Five surface-sterilized fruits were wound-inoculated with 50 µl of a conidial suspension (1 × 106 conidia/ml). After 10 days of incubation in a plastic chamber (25°C, 90% relative humidity, and 12-h photoperiod), typical anthracnose lesions developed on inoculated fruits. Five control fruits inoculated with sterile distilled water remained asymptomatic. The experiment was repeated once. Fungal colonies reisolated from the lesions showed the same morphological features as the original isolate. Pathogen was not reisolated from the control fruits. C. fioriniae was previously reported on European pear fruits in Croatia (Ivic et al. 2013), France (Da Lio et al. 2017), China (Fu et el. 2019), and in the USA (Pavlovic et al. 2019). To our knowledge, this is the first report of anthracnose of pear fruit caused by C. fioriniae in Serbia. Currently, the economic impact of anthracnose caused by this pathogen is minimal, but its presence decreases commercial value and quality of pear fruits, and can be a risk to the further spread of C. fioriniae to other plant species.

An Overview of the Emergence of Plant Pathogen 'Candidatus Liberibacter solanacearum' in Europe.

In this paper, a comprehensive overview of the 'Candidatus Liberibacter solanacearum' presence in Europe was provided. The analyzed findings revealed that, since the first appearance of this pathogen in Finland and Spain in 2008, it has spread to 13 new European countries. Therefore, 'Ca. L. solanacearum' has spread very quickly across the European continent, as evident from the emergence of new host plants within the Apiaceae, Urticaceae, and Polygonaceae families, as well as new haplotypes of this pathogen. Thus far, 5 of the 15 'Ca. L. solanacearum' haplotypes determined across the globe have been confirmed in Europe (haplotypes C, D, E, U, and H). Fully competent 'Ca. L. solanacearum' vectors include Bactericera cockerelli, Trioza apicalis, and B. trigonica; however, only T. apicalis and B. trigonica are presently established in Europe and are very important for plants from the Apiaceae family in particular. Moreover, psyllid species such as B. tremblayi, T. urticae, and T. anthrisci have also been confirmed positive for 'Ca. L. solanacearum'. Constant monitoring of its spread in the field (in both symptomatic and asymptomatic plants), use of sensitive molecular diagnostic techniques, and application of timely management strategies are, therefore, of utmost importance for the control of this destructive pathogen.

Germination and the Initial Seedling Growth of Lettuce, Celeriac and Wheat Cultivars after Micronutrient and a Biological Application Pre-Sowing Seed Treatment.

Seed treatments with zinc, boron, biostimulant Coveron and MIX (zinc + boron + Coveron) were applied to three lettuce and three celeriac cultivars. Seeds of three wheat cultivars were treated under laboratory conditions with Trichoderma harzianum and eight Bacillus spp. Seed germination, seedling growth, and the presence of the following pathogens were determined: Fusarium sp., Alternaria sp., Penicillium sp., and Mucor sp. The Coveron treatment was the most effective on lettuce seeds tested in the germination cabinet. Seed germination was higher by 4% than in the control. Alternatively, germination of seeds treated with boron in the greenhouse was higher by 12% than in the control. The Coveron treatment had the highest effect on the shoot length, which was greater by 0.7 and 2.1 cm in the germination cabinet and the greenhouse, respectively. This treatment was also the most effective on the root length. Zn, B, and MIX treatments increased celeriac seed germination by 14% in the germination cabinet. The Zn treatment was the most efficient on seeds tested in the greenhouse. The germination was higher by 15%. A significant cultivar × treatment interaction was determined in both observed species under both conditions. The maximum effect on wheat seed germination (8%) was achieved with the T. harzianum treatment in the Salazar cultivar. A significant interdependence (p ≤ 0.01 to p ≤ 0.001) was established between seed germination and the seedling growth. The interrelationship between seed germination and pathogens of all cultivars was negative.

Characterization of Pseudomonas syringae pv. syringae, Causal Agent of Citrus Blast of Mandarin in Montenegro.

Citrus blast caused by bacterium Pseudomonas syringae is a very important disease of citrus occuring in many areas of the world, but with few data about genetic structure of the pathogen involved. Considering the above fact, this study reports genetic characterization of 43 P. syringae isolates obtained from plant tissue displaying citrus blast symptoms on mandarin (Citrus reticulata) in Montenegro, using multilocus sequence analysis of gyrB, rpoD, and gap1 gene sequences. Gene sequences from a collection of 54 reference pathotype strains of P. syringae from the Plant Associated and Environmental Microbes Database (PAMDB) was used to establish a genetic relationship with our isolates obtained from mandarin. Phylogenetic analyses of gyrB, rpoD, and gap1 gene sequences showed that P. syringae pv. syringae causes citrus blast in mandarin in Montenegro, and belongs to genomospecies 1. Genetic homogeneity of isolates suggested that the Montenegrian population might be clonal which indicates a possible common source of infection. These findings may assist in further epidemiological studies of this pathogen and for determining mandarin breeding strategies for P. syringae control.