Australasian Plant Pathology最新文献

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.

Verticillium wilt is a major disease in a wide variety of crops and is caused by the fungus Verticillium dahliae Kleb. In Australian cotton growing regions two pathotypes of V. dahliae are described, namely non-defoliating and defoliating, classified on their ability to cause defoliation in cotton (Gossypium hirsutum) as well as okra (Abelmoschus esculentus) and olives (Olea europaea). Herein we report the genomes of two isolates of V. dahliae, one predicted to be non-defoliating and the other predicted to be defoliating. Phylogenomic analysis places each isolate into separate clades, but the highly aggressive, predicted defoliating, strain lacks the genomic features reported as important for causing defoliation on cotton in other regions.

In the deciduous fruit industry, orchards are often excavated and trees chipped. The organic material is then used as mulch for soil conservation, a practice that form part of sustainable agricultural. The presence and possible transmission of plant pathogens are not considered when trees are removed, chipped and used for mulch. Young apple trees can develop cankers due to Diplodia seriata of which the inoculum source might come from fruiting structures present on apple wood mulch. Therefore, the presence of D. seriata, on chipped apple tree wood pieces used for mulch in younger orchards was investigated. To be able to detect D. seriata, qPCR primers were designed from a previously identified unique sequence characterised amplified region (SCAR). The qPCR primers were specific for D. seriata (Cq ≤ 35 and Tm = 85(:pm:)0.17 °C) when compared with DNA from nineteen other fungal taxa associated with canker or wood rot of apple trees tested, excluding Botryosphaeria dothidea (Cq = 38 and Tm = 85.25 °C). The qPCR assay was sensitive and had a limit of quantification of 2859 fg/µl and limit of detection of 571 fg/µl. Wood chips were collected at two time periods (from heaps and 6 months after it was spread in tree rows) in three apple orchards in the Western Cape of South Africa. DNA was extracted from water-washes of 120 wood piece samples and D. seriata was detected from 101 of these samples. This study showed that the newly developed primers was able to successfully detect D. seriata from mulched apple wood. The presence of D. seriata on apple tree wood chips indicates that there is a risk involved in using wood chips made from old apple trees.

Anacardium occidentale is the tree source of cashew nuts, a commodity with increased demand globally and threatened by several diseases. Here we report on the occurrence of a disease that has severely affected production of cashew nuts in Panama and that can be of regional importance. Our first observation of this disease was in 2013, in the locality of Gamboa (Colon, Panama). Blight symptoms of the disease starts with foliar lesions characterized by initial necrotic points surrounded by yellow discoloration or chlorotic zones. These lesions progressively expand, transforming into larger, brown patches with rounded to irregular shapes. Lesions can coalesce and cover entire leaves causing them to drop and produce defoliation of entire branches or trees that become unproductive. Trees with similar symptoms were later observed in several provinces in Panama indicating that the disease was widespread in the country. We obtained consistent isolation of the same fungus from lesions on A. occidentale from multiple localities and pathogenicity tests were conducted on detached leaves as well as on healthy leaves on an adult tree. Morphological and phylogenetic analyses of the isolated fungus showed that the causal agent was Calonectria variabilis, a fungus previously reported to occur on Schefflera morototoni, Theobroma grandiflora, and Eucalyptus. This is the first time that C. variabilis is reported as a pathogen of A. occidentale and the first record of this species for Panama.