Australasian Plant Pathology最新文献

The research focuses on the spatial distribution of grape downy mildew in different vineyards across major districts in Karnataka, India. Covering 6 administrative districts, 14 taluks, and 130 villages, the study employs geostatistical techniques, including GIS, point pattern analysis, and interpolation, to assess the severity and spatial patterns of the disease. Utilizing a 0–9 severity scale, the investigation reveals varying degrees of downy mildew infection in surveyed areas, with potential clusters identified through spatial analysis. District-wise and taluk-specific analyses highlight variations in disease severity, with Doddaballapura exhibiting the highest index at 64.21%, and the lowest at 20.12% in Bagalkot. Agglomerative hierarchical cluster analysis identifies two main clusters among the surveyed districts, providing insights into regional disease patterns. Spatial point pattern analysis, including Local Moran’s I and Ripley’s K function, confirms the presence of clusters and offers a deeper understanding of disease dynamics. Interpolation techniques, such as IDW, reveal inconsistent disease occurrence across locations, emphasizing the need for targeted intervention. Ordinary and indicator kriging provide detailed spatial maps, showing disease severity hot spots in southern Karnataka and select areas in Bijapur district. The study underscores the urgency of addressing the growing threat of grape downy mildew, offering scientifically robust insights for disease management strategies in Karnataka’s diverse grape ecosystems.

In 2019, symptoms typical of infection by iris yellow spot virus (IYSV; family Tospoviridae, genus Orthotospovirus) were observed on shallot (A. cepa var. aggregatum) grown at the Gatton Research Facility, Department of Agriculture and Fisheries, Queensland. Initial testing by DAS-ELISA was positive for IYSV, and subsequent specific RT-PCR amplifying part of the RdRp (L-segment) and sequencing of amplicons confirmed the IYSV infection. This is the first record of IYSV infection of shallot in Australia.

Leaf spot (LS) (Pseudocercospora vitis) and ripe rot (Colletotrichum spp.) cause significant losses to rustic grapevine cultivar ‘Bordo’ (Vitis labrusca), which is cultivated for juice production. The demand for juice from organic agriculture has been growing, resulting in the need for biorational products to manage disease with more environmentally friendly products. In this study, the potential of two products were evaluated in the field for managing LS and RR in the cultivar ‘Bordô’ over two seasons. The bacterial suspensions of Bacillus alcalophilus and eugenol acetate + potassium bicarbonate (750 mg L^− 1) applied with conventional spraying (first season) and conventional and electrostatic spraying (second season) were assessed for disease control. Standard winter treatments, along with pest and weed control was performed. Severity of LS was evaluated over time, and the area under the disease progress curve (AUDPC) was used to compare treatments. RR incidence was assessed at harvest and post-harvest during storage, simulating the commercialization period. With post-harvest disease data, the relative risk of ripe rot symptom expression was calculated. B. alcalophilus in both seasons and, eugenol acetate with electrostatic application in second season reduced LS severity. Electrostatic and conventional spraying did not differ in disease control potential in the evaluated season. The ripe rot symptoms achieved 67% of incidence in the control treatment and the treatments tested were not effective in reducing the incidence of the disease. Cluster weight and total soluble solids did not differ between treatments. The biorational products tested are not effective for ripe rot control, however, they may be recommended for LS control in an organic system.

Sri Lankan cassava mosaic virus (SLCMV) is one of the viruses that cause cassava mosaic disease. Strong mosaic symptoms on a cassava plant in the Northern Territory tested positive in begomovirus specific PCR testing. The DNA sequence of the amplicon was 96.38% similar (over 528 bp) to SLCMV, a result confirmed by sequencing genomic DNA. This is the first record of SLCMV in Australia, and outside of Asia.

Pomegranate (Punica granatum L.) is an important fruit species for both human nutrition and the pharmaceutical industries, and is also an important export product for Türkiye. Pomegranate root and collar rot caused by Phytophthora nicotianae and P. palmivora is the main disease of this crop and the major limiting factor in production in Türkiye. The susceptibility of ten pomegranate cultivars to P. nicotianae and P. palmivora was investigated. One-year-old plants of ten cultivars (Asinar, Fellahyemez, Hicaznar, Katirbasi, BATEM-Hicrannar, BATEM-Esinnar, BATEM-Onurnar, BATEM-Yilmaznar, Izmir-23 and Izmir-1513) were tested using a soil infestation technique. At the end of the experiment, root weights significantly decreased and it was concluded that all cultivars were susceptible to the pathogens. In addition, leaf blight caused by Alternaria alternata, one of the most widespread foliar diseases of pomegranate in Türkiye, was frequently observed on the leaves of the plants inoculated with Phytophthora spp., while there was little disease on the leaves of control plants. This finding confirmed that plants under stress were more susceptible to pathogen infections. All isolates of P. nicotianae and P. palmivora obtained from pomegranate orchards were sensitive to mefenoxam. While EC₅₀ values of P. nicotianae isolates were between 1.774 and 1.918 μg ml^− 1, those of P. palmivora were between 1.895 and 1.944 μg ml^− 1.

This study aims to collect comprehensive research findings on Fusarium Head Blight (FHB) disease, where the host plant, wheat, was discussed in terms of its economic importance worldwide and then in Algeria, followed by addressing the economic significance of the disease in terms of its impact on both the yield and the health quality of the grain. After that, the causative agents were addressed, including the most important species of the Fusarium genus, its geographical distribution, life cycle, and, finally, the most essential methods used in identification. Research was also done on the study of the essential mycotoxins produced by Fusarium species in terms of their types and chemical composition. On the other hand, various strategies for controlling FHB were discussed, such as searching for resistant wheat varieties, cultural, chemical, biological, and possible integrated control.

Paris polyphylla var. yunnanensis is an important perennial medicinal plant whose production is greatly limited by various diseases, including leaf spot disease recently reported in Yunnan, China. However, the causative agent of P. polyphylla leaf spot is still unknown. This study isolated and identified the causal agent of P. polyphylla leaf spot from leaf tissues of infected plants through morphological and molecular characterization. The isolated fungus was identified as Alternaria alternata based on its morphological characteristics and nucleotide sequences of the elongation factor 1-alpha (EF1α), nuclear ribosomal internal transcribed spacer (ITS), the 28S nuclear ribosomal large subunit rRNA gene (LSU), the 18S nuclear ribosomal small subunit rRNA gene (SSU), and the second largest subunit of nuclear DNA-directed RNA polymerase II (RPB2). The re-isolation of the isolate fulfilled Koch´s postulates, indicating that A. alternata was the causal agent of P. polyphylla leaf spot. The findings of this study will potentially pave the way for epidemiological forecasting and developing control strategies for this disease.

Botryosphaeriaceae species are important latent pathogens causing diseases on trees utilized in forestry and agriculture. In recent years, there has been an increase in the incidence and severity of branch dieback and decline on macadamia trees in South Africa, and species of Botryosphaeriaceae have been considered as a possible cause. Although botryosphaeria dieback has been well-studied in Australia, there is little information regarding these fungi on Macadamia in South Africa. The aims of this study were consequently to (i) identify species of Botryosphaeriaceae from Macadamia branches from main production regions in South Africa, (ii) compare the diversity of species between symptomatic and asymptomatic branches, as well as between different growing regions, (iii) and to consider their relative importance in causing dieback. Eight species and three putative hybrids of the Botryosphaeriaceae were identified based on a phylogenetic comparison of sequence data from the ITS rDNA, tub2, tef-1α and rpb2 loci. These included an unidentified Diplodia sp., and Lasiodiplodia sp., as well as L. gilanensis, L. theobromae, L. pseudotheobromae, Neofusicoccum kwambonambiense, N. luteum, N. parvum and three hybrid species. The unidentified species of Diplodia., Lasiodiplodia sp., L. gilanensis, and N. kwambonambiense are reported for the first time on Macadamia in South Africa. All species showed a potential to cause branch dieback symptoms, with species of Neofusicoccum identified as the most aggressive species. This study revealed a high level of diversity of Botryosphaeriaceae species and illustrates their potential as causal agents of dieback on Macadamia in South Africa.

Corm rot of saffron is the deadliest disease of saffron and a major bottleneck in its successful cultivation in Jammu and Kashmir, India. To date, only limited information has been made available for the monitoring, surveillance, and detection of plant pathogens associated with corm rot of saffron in this region. Incidence and severity of corm rot caused by multiple pathogens, viz., Fusarium oxysporum, Fusarium solani, Aspergillus niger, Penicillium corymbiferum, Rhizoctonia solani, and Macrophomina phaseolina, was assessed in saffron growing regions based on multiple field surveys conducted at the farmer’s fields in Kishtwar district of Jammu and Kashmir, during June-July 2021 and 2022. Corm rot was prevalent in all the surveyed prefectures of the saffron growing region, with a maximum disease incidence (62.02%) and severity (43.68%) at Lower Pochhal. The disease manifested as yellowing, drooping, and wilting of shoots during flowering, resulting in dying of the foliage which subsequently led to rotting of corms. Association of six fungal species viz., Fusarium oxysporum, Fusarium solani, Aspergillus niger, Penicillium corymbiferum, Rhizoctonia solani and Macrophomina phaseolina was recorded from the infected saffron corms based on morphological characteristics. Out of these, F. oxysporum was the predominant pathogen, and was present in all the surveyed locations. Species specific SCAR (Sequence Characterized Amplified Region) primers (FO-SCAR-FP and FO-SCAR-RP) were designed for effective detection and diagnosis of F. oxysporum, as it emerged as the major pathogen. Results of the present study may provide new insights into the monitoring of the corm rot and the deployment of an effective disease management strategy that will enhance the production, and productivity of saffron. This being the first comprehensive survey in the region, it provides basic information regarding the occurrence of disease, the distribution of various pathogens associated with it and also about the detection and monitoring of F. oxysporum.

The cowpea chlorotic mottle virus (CCMV) was detected in forage peanut plants (Arachis pintoi), showing mosaic, yellowing, and interveinal chlorosis. Negatively stained partially purified preparations contained isometric particles ca. 30 nm in size, also present in the cytoplasm and vacuole of leaf parenchymal cells from CCMV-infected A. pintoi leaves. Mechanical transmission of the CCMV leaf extracts from symptomatic A. pintoi plants resulted in systemic mosaic in A. pintoi cv. BRS Mandobi, Vigna unguiculata L. cv Pretinha, and V. unguiculata sg. sesquipedalis cv. De Metro plants; mottle on leaves of inoculated Nicotiana occidentalis and N. benthamiana; and local necrotic and chlorotic lesions in Chenopodium quinoa and C. amaranticolor, respectively. High-throughput sequencing (HTS) allowed us to identify the causal agent as the CCMV and obtain the complete nucleotide sequence of the three genome components. BLAST search in the nucleotide database revealed high identities of the genome components with previously reported CCMV isolates. Primer was designed based on the HTS-derived sequence and efficiently detected CCMV in the infected A. pintoi samples. To our knowledge, this is the first report of CCMV infecting forage peanuts.