Features of ion generation by a picosecond laser in the range of 1011 – 1013 W/cm2 power densities

Picosecond lasers (ps-lasers) have significant advantages for the generation of low charge state ions compared to nanosecond lasers because the influence of heat conductivity on a solid target is almost negligible in the case of ps-laser ablation for laser pulse durations less than 10 ps. However, there is no comprehensive data on ion yields for different elements and target irradiation conditions for laser power densities at the target surface around and below 1013 W/cm2, which is of interest to our study of such plasmas as a source of low charge state ions for various applications, particularly for external injection of those ions into an Electron Beam Ion Source (EBIS). We investigated ion generation from Al, Ti, Cu, Nb and Ta target elements by a ps-laser with power densities in the range of 1011 – 1013 W/cm2 at the target surface. A ps-laser with 1.27 mJ maximum energy within an 8 ps pulse and repetition rate up to 400 Hz has been used to generate a laser-ablated plasma. Dependencies of ion current vs time, total charge of registered ions as well as ion kinetic energy distributions are characterized using a Faraday cup. Significant difference in ion current dynamics between first, second and following shots onto the same target spot was found for all five target elements. The total charge of ions registered by the Faraday cup increases linearly with increasing laser pulse energy and is almost independent of the target element and number of shots onto the same target spot for all five target elements studied. The results obtained give us a basis for specification and design of the source of low charge state ions for external injection into EBIS.

Identification of Tomato Leaf Diseases Using Deep Convolutional Neural Networks

Crop disease is a major issue now days; as it drastically reduces food production rate. Tomato is cultivated in major part of the world. The most common diseases that affect tomato crops are bacterial spot, early blight, septoria leaf spot, late blight, leaf mold, target spot, etc. In order to increase the production rate of tomato, early identification of diseases is highly required. The existing work contains very less accurate system for identification of tomato crop diseases. The goal of our work is to propose cost effective and efficient deep learning model inspired from Alexnet for identification of tomato crop diseases. To validate the performance of proposed model, experiments have also been done on standard pretrained models. The plantVillage dataset is used for the same, which contains 18,160 images of diseased and non-diseased tomato leaf. The disease identification accuracy of proposed model is compared with standard pretrained models and found that proposed model gave more promising results for tomato crop diseases identification.

Identification of Tomato Leaf Diseases using Deep Convolutional Neural Networks

Crop disease is a major issue now days; as it drastically reduces food production rate. Tomato is cultivated in major part of the world. The most common diseases that affect tomato crops are bacterial spot, early blight, septoria leaf spot, late blight, leaf mold, target spot, etc. In order to increase the production rate of tomato, early identification of diseases is highly required. The existing work contains very less accurate system for identification of tomato crop diseases. The goal of our work is to propose cost effective and efficient deep learning model inspired from Alexnet for identification of tomato crop diseases. To validate the performance of proposed model, experiments have also been done on standard pretrained models. The plantVillage dataset is used for the same, which contains 18,160 images of diseased and non-diseased tomato leaf. The disease identification accuracy of proposed model is compared with standard pretrained models and found that proposed model gave more promising results for tomato crop diseases identification.

Detection of the G143A Mutation in the Cytochrome b Gene of Corynespora cassiicola Isolates from Soybean in Tennessee

Corynespora cassiicola is the causal pathogen of target spot in soybean and cotton grown in the United States. With target spot increasing in importance, fungicides are becoming an important tool for control of this disease. Unfortunately, there are reports of C. cassiicola isolates in other crops being resistant to some fungicide classes. The objective of this study was to identify if resistance to quinone outside inhibitor (QoI) fungicides is present in Tennessee soybean and cotton isolates of C. cassiicola. Four isolates of C. cassiicola were evaluated at a range of doses for the fungicide pyraclostrobin. Isolates were also sequenced to determine if the G143A mutation was present in the cyt b gene. Two isolates previously reported to be resistant to QoIs were also used as positive checks. Two isolates of C. cassiicola from Tennessee soybean were found to have the G143A mutation. EC50 values for the two isolates ranged from 15.7 to 121 μg/ml. As a result of this study, C. cassiicola isolates have exhibited resistance to QoI fungicides in Tennessee soybean.

Etiology, Epidemiology and Management of Asian Soybean Rust (ASR) in Brazil and Vulnerability of Chemical Control of Specific without Multisite Fungicides

Brazil is the first soybean producer in the world, and the largest exporter. In the 2019/20 harvest, the country produced about 124.85 million tons, representing 30% of world production. Global soy production for 2019/20 reached 337.9 million tons. Asian soybean rust (ASR) is the most pathogen on soybean in Brazil in nowadays. Target spot and Septoria leaf spot plus white mold complete these scenarios. ASR emerged in Brazil in 1979. The use of fungicides in the soybean crop in Brazil intensified after the master of 2002 with the resurgence of soybean rust, where the use of triazoles intensified. The massive sprays to pathogen control reached 3.5 sprays per season. In 2006, the first reports of loss of sensitivity of the fungus to the group appeared, notably for the fungicide flutriafol and tebuconazole used in many situations in a curative way or to eradicate the fungus. From that moment on, the productive system sought to use triazoles and strobilurins. In 2011 came the first reports of loss of sensitivity of the fungus in the group of strobilurins. This fact was due to the use of pyraclostrobin in the vegetative phase of soybeans without protection by multisite. That same year, the introduction of the active ingredients in copper oxychloride, mancozeb and chlorothalonil took place in Brazil. In 2015, the first carboxamides ((benzovindiflupyr) (solatenol and fluxpyroxade) associated in triple mode with triazoles and strobilurins were launched on the Brazilian market. Due to the specific mode of action in the metabolism of the fungus (biosynthesis of ergosterol (triazoles), mitochondrial respiration in the cytochrome oxidase enzyme complex - QOIs (strobilurins) and succin dehydrogenase - SDHIs (carboxamides), the need for their association in the sprayings was seen. To multisite (cuprics, dithiocarbamates and nitriles). For the sustainable management of the disease in Brazil, control strategies are recommended, such as the use of systemic fungicides, with a specific biochemical mechanism of action with the adoption of tank mix with multisite, adoption of cultural practices (sanitary emptiness) and sowing schedule and the use of varieties with quantitative resistance (partial or horizontal resistance). These measures will guarantee the sustainability of the culture and the useful life of systemic fungicides or specific sites.

Detection of a Point Mutation (G143A) in Cyt b of Corynespora cassiicola That Confers Pyraclostrobin Resistance

Point mutation G143A in the cytochrome b (Cyt b) protein commonly confers resistance to quinone outside inhibitor (QoI) fungicides in phytopathogenic fungi, including Corynespora cassiicola, which causes cucumber target spot disease. However, the effect of G143A on the binding between the QoI fungicide and the Cyt b protein, and the use of LAMP (loop-mediated isothermal amplification) to detect this point mutation had not been reported previously in C. cassiicola. In this study, the sensitivity of 131 C. cassiicola isolates—collected from Shandong province, China in 2019 and 2020—to pyraclostrobin was determined. The EC50 values ranged from 1.67 to 8.82 μg/mL, and sequencing results showed that all C. cassiicola isolates contained the G143A mutation. Molecular docking results suggested that G143A significantly alters the affinity of pyraclostrobin to the Cyt b protein. Following development of three LAMP primer pairs, the best reaction condition for LAMP analysis was 65 °C for 60 min, and the detection limit was 0.01 ng/μL of DNA containing the point mutation. In conclusion, the G143A mutation conferring pyraclostrobin resistance is widespread in C. cassiicola from Shandong province, and the LAMP method can be used to monitor QoI resistance in C. cassiicola caused by the G143A mutation in the field.

First Report of Corynespora cassiicola Causing Target Spot on Soybean in Taiwan

Soybean (Glycine max [L.] Merr.) is an important crop in Taiwan. In October 2020, an unknown leaf spot disease was counted (n = 100) to occur over 70% of soybean cultivar ‘Hualien No.1’ in the Shoufeng Township of Hualien County, eastern Taiwan. Initial symptoms on leaves as tiny lesions approximately 3 mm in diameter, which later enlarged and developed into round, irregular, and reddish-brown spots with concentric rings surrounded by a yellowish halo. The symptoms appeared on both young and old leaves, but rarely on the stem or pods. The lesions at the margin of healthy and infected tissues were surface-disinfested in 1% NaOCl for 30 seconds, washed twice in sterilized distilled water, dissected and plated on potato dextrose agar (PDA) to isolate the potential pathogen. Colonies on PDA exhibited light to dark brown color at 24°C with 12-hours light after 7-days incubation. The average growth rate was 3 mm per day. Conidia were light brown in color and obclavate to cylindrical in shape. The size of a conidium was measured with an average of 110.8 ± 28.2 μm in length and 15.2 ± 2.8 μm in width, typically with 3 to 18 septa (n = 50). To confirm the pathogenicity of this fungus, conidial suspension (104 conidia/mL) of two isolates, HL_GM-6 and HL_GM-7, were sprayed on the healthy leaves of 4-weeks-old soybean. Plants sprayed with sterile distilled water were used as a control. After inoculation, the plants were covered with plastic bags to maintain a high humidity for 24 hours before moving into a greenhouse with a condition of 20 to 25°C and relative humidity of 75 to 80%. After 7 days of inoculation, foliar symptoms began to appear and which were identical with the field observations. To complete the Koch’s postulates, pathogen isolation was attempted and the identical fungus was retrieved from the foliar spots of the inoculated leaves. The foliar symptoms as well as the morphology of the conidiophores and conidia suggested the pathogen to be Corynespora cassiicola (Ellis et al. 1971). Molecular characterization was performed using the sequences of internal transcribed spacer (ITS) region of rDNA, actin (act1), tubulin, and translation elongation factor 1 alpha (tef1) genes after a PCR with ITS1/ITS4 (White et al. 1990), ACT-512F/ACT-783R (Carbone and Kohn, 1999), BT2a/Bt2b (Udayanga et al. 2012), EF1-728F/EF1-986R (Udayanga et al. 2012), respectively. BLASTN sequence analyses of the ITS, act1, tubulin, and tef1 genomic regions of the isolate HL_GM-7 (GenBanK accessions MW548097 MW961420, MW961419 and MW961421) showed high similarity with the isolates of C. cassiicola including 99.58% with sequence KF810854 (Deon et al. 2014), 99.11% with FJ853005 (Dixon et al. 2009), 99.34% with MH763700 (Duan et al. 2019), and 99.33% with KY112719 (Zhang et al. 2018) respectively. Based on the morphology, pathogenicity, and sequence results, this study becomes the first report of C. cassiicola causing target spot on soybean in Taiwan. C. cassiicola is known to infect a broad host range (Dixon et al. 2009; Lopezet al. 2018), and it has been found to infect tomato, cucumber, papaya, and Salvia miltiorrhiza in Taiwan (Lu et al. 2019; Tsai et al. 2015). Therefore, the emergence of soybean target spot should be aware to avoid potential damage to soybean production in Taiwan.