Journal of Plant Diseases and Protection最新文献

Over the past decades, European ash trees in Germany have been affected by ash dieback, reducing their vigour and mechanical resistance. Those trees that also have stem collar necroses and the resulting stem rot are particularly affected. In this study, multilocus genotypes (MLGs) of Hymenoscyphus fraxineus and their interactions with other fungi from stem collar necroses were analysed. Ten ash trees from three different adjacent forest stands in central Germany were sampled. A total number of 716 isolates were obtained from stem collar necroses from these ten trees. Microsatellite analysis was successfully performed on 274 isolates identified as H. fraxineus and 26 MLGs were revealed. The number of MLGs varied from one to seven per tree and did not correspond to the number or severity of necroses. A striking result was that five of the MLGs occurred in two trees. All other MLGs occurred independently in only one tree, as expected. Our data show that when multiple MLGs were observed in a tree, one of the MLGs outnumbered the others, indicating that H. fraxineus is a primary coloniser of stem collar necroses. A total of 61 morphotypes, including H. fraxineus, were identified and discussed, comprising endophytic, saprotrophic and pathogenic fungi. Between five and 19 different fungi were found per stem collar necrosis. The majority of all isolated morphotypes were Ascomycota (82%), with the most common orders being Xylariales and Hypocreales. The most frequently isolated morphotypes, apart from H. fraxineus, were Armillaria sp. and Diplodia fraxini. Together they account for more than three quarters of all assigned isolations. Apart from H. fraxineus, only Diplodia fraxini was isolated from all ten trees.

Plant disease diagnosis in smart agriculture is a crucial issue that carries substantial economic significance on a global scale. To address this challenge, intelligent and smart agricultural solutions are currently being developed to assist farmers in implementing preventive measures to increase crop production. As deep learning technology continues to evolve, many convolutional neural network (CNN) models have emerged as highly effective for detecting plant leaf diseases. These CNN-based models require heavy computation and processing cost. So, this paper develops a new lightweight deep convolutional neural network named lightweight DenseNet (LWDN) for detection of plant leaf disease for agricultural applications. Based on the DenseNet121 architecture, the presented model comprises pruned and concatenated architecture of DenseNet121. The presented study involved training and testing a proposed model (LWDN) on the PlantVillage dataset to acquire a knowledge of plant disease features. The model was trained using a combination of partial layer freezing, transfer learning, and feature fusion techniques. Out of several models experimented with, the proposed model has 99.37% classification accuracy, a model size of 13.8 MB, with 1.5 M parameters. The proposed model has 93% fewer parameters than InceptionV3 and Xception and 90% and 50% fewer parameters compared to VGG16 and MobileNetV2, respectively. Furthermore, the proposed method has superior diagnostic capabilities compared to several prior studies and larger state-of-the-art models utilizing plant leaf images. The compact size and competitive accuracy of the LWDN model render it appropriate for real-time plant diagnosis on portable and mobile devices with restricted computational resources.

Plant pathogens are highly adaptable, and have evolved to overcome control measures including multiple classes of fungicides. More effective management requires a thorough understanding of the evolutionary drivers leading to resistance. Experimental evolution can be used to investigate evolutionary processes over a compressed timescale. For fungicide resistance, applications include predicting resistance ahead of its emergence in the field, testing potential outcomes under multiple different fungicide usage scenarios or comparing resistance management strategies. This review considers different experimental approaches to in vitro selection, and their suitability for addressing different questions relating to fungicide resistance. When aiming to predict the evolution of new variants, mutational supply is especially important. When assessing the relative fitness of different variants under fungicide selection, growth conditions such as temperature may affect the results as well as fungicide choice and dose. Other considerations include population size, transfer interval, competition between genotypes and pathogen reproductive mode. However, resistance evolution in field populations has proven to be less repeatable for some fungicide classes than others. Therefore, even with optimal experimental design, in some cases the most accurate prediction from experimental evolution may be that the exact evolutionary trajectory of resistance will be unpredictable.

Rockmelon is a popular tropical fruit with high nutritional value. Cucumber mosaic virus (CMV), an aphid-transmitted virus, causes severe damage to rockmelon production. Exogenous application of double-stranded RNA (dsRNA) targeting viral sequences has shown promising results in controlling viral infection but has not been reported for CMV in rockmelon. In the current study, the protective effect of exogenous dsRNAs targeting the CMV coat protein (CP) and movement protein (MP) was tested in rockmelon. The effectiveness of dsRNA-mediated protection was measured by disease severity index (DSI) and compound enzyme-linked immunosorbent assay. The individual dsRNA CP and MP treatments each showed protection by reducing the DSI and virus titre, whilst a combination of dsRNA of CP and MP treatment showed much lower DSI (4.31-fold lower) and virus titre (4.91-fold lower) compared to CMV-inoculated plants without dsRNA treatment. Chlorophyll content, relative water content, plant height and number of leaves were not significantly different between virus challenged dsRNA-treated and mock-inoculated plants. Based on the DSI, two applications containing 9000 ng of dsRNA CP and MP in combination showed maximum CMV protection. Taken together, these results indicate that exogenous treatment containing a combination of dsRNA of CP and MP can control CMV infection in rockmelon.

Fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), is a serious invasive insect pest affecting global maize production. Effective integrated management of FAW is essential to minimize the yield losses. The objective of this study is to determine a suitable package for the sustainable management of FAW by validating the potentiality of various integrated approaches through field trials. In the present study, five different integrated pest management treatments consisted of different components were synthesized and evaluated against fall armyworm in maize-based systems during winter (December 2022–April 2023) and rainy (July–November 2023) seasons. The data on the number of plants damaged, leaf damage rating (1–9 scale), and natural enemies such as spiders, coccinellids, and earwigs were recorded from 20 randomly selected plants at 7 and 14 days after the first and second sprays. Yield data (q ha⁻¹) were recorded at the time of harvest. Treatment 1 consisting of pheromone traps at a rate of 4 per acre with ICAR-NBAIR lures, erection of bird perches at a rate of 10 per acre, seed treatment with Chlorantraniliprole 50 FS at a rate of 5.6 ml per kilogram of seed, and spray application of azadirachtin 1500 ppm at the rate of 5 ml per litre, and Metarrhizium anisopliae with spore count of 1 × 10⁸ cfu/g (1 kg per acre) at a rate of 5 g per litre significantly reduced the per cent plant infestation (12.7) and leaf damage rating (2.1) by FAW larvae compared to untreated control (39.7, 4.1), respectively. The higher natural enemy population (spiders, coccinellids, and earwigs) was also observed in Treatment 1 (8.8) compared to Treatment 5 (4.1) (chemical control). Furthermore, higher grain yield of 51.5 q ha⁻¹ was obtained in Treatment 1 with a cost–benefit ratio of 1:2.1, whereas in untreated control, the yield obtained was 29.0 q ha⁻¹ with a cost–benefit ratio of 1:1.3. The highest per cent of avoidable yield losses of 43.6 was observed in Treatment 1 in comparison with other treatments. Integration of sustainable management approaches reduces the application of chemical insecticides and enhances the population of natural enemies which would be beneficial to maize farmers.

The whitefly Bemisia tabaci (Gennadius, 1889) (Hemiptera: Aleyrodidae) is a globally important insect pest, causing extensive damage and losses in horticultural production systems. New natural options are needed to control the whitefly. Ethanol extracts (92) of different organs from 40 plant species of the Yucatan Peninsula were evaluated against B. tabaci in a greenhouse, and an adult repellency index (RI) was determined for leaves and an oviposition deterrence index (ODI) for the extracts. Ethanol extracts at 1% (w/v) after 48 h suppressed the population density of B. tabaci. Leaves of Malpighia glabra L. had the highest repellent activity, causing a decrease in the population density of adults (RI 0.05) and eggs (ODI − 85). Three fractions differing in polarity were obtained by partitioning the ethanol extract of M. glabra, and the hexane fraction had an intermediate RI, but the ODI was not active. LC–UV–HRMS analysis of the fractions showed the presence of syringaresinol, 10-hydroxy-pheophorbide a, pheophorbide a, and lupenone, the first report of these four for this species. Eleven unknown compounds were also detected. This bioprospecting research on botanical extracts from native species of the Yucatan Peninsula enriches our knowledge of potential sources of products for pest management. M. glabra is a promising candidate for further formulation and application studies to control B. tabaci.

We established confrontations between two different fungi, i.e., the maize anthracnose and stalk rot pathogen Colletotrichum graminicola, and the ubiquitous fungus Aspergillus nidulans, and different biocontrol species, i.e., Bacillus subtilis, Bacillus velezensis, and Bacillus amyloliquefaciens. In all fungus–bacterium confrontations tested, growth arrest and, thus, distance inhibition was observed on solid substrata. LC–MS/MS analyses of culture filtrates suggested formation of several metabolites only synthesized in confrontations. Interestingly, microscopy of fungal hyphae grown in liquid medium showed protrusions and color changes occurred only in media harboring fungus-bacterium confrontations. These observations indicate metabolic re-programming and suggest formation of putative secondary metabolites in interactions involving microbial biocontrol agents.

Abstract

Ramularia leaf spot of barley, caused by Ramularia collo-cygni has become a serious disease threat to barley production. By inducing necrotic lesions, the disease expiates the onset of leaf senescence, which can result in significant grain yield and quality losses. In addition to surviving between seasons in trash, stubble and volunteers, R. collo-cygni can be transmitted from seed to emerging seedlings. As a potential additional means of transmission it may also pose a risk for the spread of specific traits such as fungicide resistance. In the present study, we screened Irish barley seed stocks harvested in the years 2015–2017 for the presence of R. collo-cygni using qPCR, and subsequently using an amplicon sequencing assay screened for the presence of alleles in the SDHC gene of R. collo-cygni associated with SDHI resistance. Over the three year period > 60% of the samples screened had detectable levels of R. collo-cygni present. In a subsample of these five alleles associated with resistance (SDHC—N87S, G91R, H145R, R152M and H153R) were detected. The prevalence of the key alleles C-N87S and C-H146R remained stable over the three year period, and was similar to that detected amongst an isolate collection established in 2022.

Zabrotes subfasciatus (Boheman) is one of the main pests of storage beans, affecting common bean (Phaseolus vulgaris L.) in tropical world regions. The aim of this study was to evaluate antixenosis of two P. vulgaris genotypes to Z. subfasciatus and the emission of volatile compounds from seeds of these genotypes. Antixenosis in adults and oviposition was evaluated using the obligate antibiosis test, on ‘G11051’ and ‘ICA Pijao’ genotypes of common bean to Z. subfasciatus. The volatile compounds of their seeds related to antixenosis were also evaluated. The number of adult insects away from seeds, the percentage of eggs in seeds and the container and the number of total eggs were counted. The presence of volatile compounds was determined by headspace solid-phase microextraction coupled with gas chromatography–mass spectrometry (HS-SPME-GC-MS). Genotype ‘G11051’ showed higher adult antixenosis (80% non-preference) and antixenosis by oviposition on their seeds than ‘ICA Pijao’ genotype which showed only 11% repellency. Significant statistical differences were found in the volatile compounds detected. ‘G11051’ showed 65 compounds and 22 specific to this genotype, while in ‘ICA Pijao’, 53 compounds were detected, eight of which were specific to this genotype. Of these, dimethyl disulfide, limonene, (E)-2-hexenal and hexanal showed known antixenotic activity.

Plant-parasitic nematodes pose a significant threat to economically important crops, causing annual losses amounting to billions of dollars. Accurate identification of these pathogens is crucial for the implementation of effective management strategies. Various methods are available for nematode species identification; however, some rely on trained taxonomists (morphological methods), specific stages of the nematode (isoenzyme electrophoresis and perineal pattern analysis) or require costly equipment and reagents (conventional or real-time polymerase chain reaction). Loop-mediated isothermal amplification is a molecular technique with the potential to offer a precise, simple, and relatively affordable diagnosis of nematode species. Although widely utilized in microbiology, human and veterinary medicine, its application in plant nematology remains relatively unexplored. This article presents a comprehensive review of the loop-mediated isothermal amplification technique, existing protocols for plant-parasitic nematode diagnosis, and the future prospects for harnessing this method in the field of plant nematology.