Australasian Plant Pathology最新文献

Diseased garlic bulbs (cv. Glenlarge) with symptoms of rot were identified in Gatton, Queensland, Australia, during storage in February 2023. The causal pathogen was identified as Fusarium oxysporum by sequencing of the TEF1 gene region, pathogenicity tests, and successful fulfillment of Koch’s postulates. This is the first report in Australia, to the author’s knowledge, of F. oxysporum causing disease in Allium sativum.

Garlic bulbs (cv. Glenlarge) that were grown in Gatton, Queensland, Australia were identified as having dry rot symptoms during storage in February 2023. The pathogen was identified as Fusarium proliferatum by sequencing of the TEF1 gene region. Pathogenicity was confirmed by Koch’s postulates. This is the first report, to the author’s knowledge, of F. proliferatum causing disease in Allium sativum in Australia.

Stripe rust is a major yield-limiting factor worldwide. The current study evaluated the response of wheat genotypes to stripe rust disease, focusing on the diversity of wheat genotypes towards stripe rust resistance. The study was conducted in the field research area of the Department of Plant Breeding and Genetics (PBG), Faculty of Agriculture and Environment, Islamia University of Bahawalpur during Rabi 2023-24. The experiment employed an augmented design that increased the precision and accuracy of the results by including additional genotypes in the experimental design. Thirty genotypes and one susceptible check variety, “Morocco”, from the Regional Agriculture Research Institute (RARI) in Bahawalpur, were tested. Disease severity varied from 0 to 100%, with some genotypes showing resistance, moderate resistance, moderate susceptibility, susceptibility, or immune responses. Data were recorded for various traits, such as plant height, number of tillers, spike length, peduncle length, spikelet per spike, thousand grain weight, grain filling period, grain yield per plant, coefficient of infection, chlorophyll content (SPAD), and disease severity percentage. The mean values of disease severity ranged from 100 to 0%, with G1 being the most susceptible and G15 being the most tolerant. A positive correlation was observed between disease severity percentage and plant height and coefficient of infection, while a negative correlation was observed between chlorophyll content, grain-filling period, and disease severity percentage, but this relationship was not statistically significant. There was negative yet non-significant relationship between thousand-grain weight, grain yield per plant, and disease severity percentage, as the regression model was not statistically significant. Genotype (G15) found as most resistant genotype against stripe rust in the available germplasm, and it can aid in breeding programs to develop new wheat cultivars with enhanced resistance to the disease.

Globisporangium recalcitrans is an important phytopathogenic oomycete that causes soybean root rot. To develop a loop-mediated isothermal amplification (LAMP)-based system for rapid and specific detection of G. recalcitrans, four LAMP primers and two loop primers were designed with the Ribosomal DNA transcribed spacer 2 sequence (ITS2) as the target gene. The specificity and sensitivity of these primers were validated, and the system was also successfully applied to detect G. recalcitrans in soybean tissues after artificial inoculation and natural infection. The nucleic acid amplification reaction was performed under isothermal conditions at 63 °C for 60 min. Specificity was compared with those for 71 strains of G. recalcitrans, other Globisporangium spp. The minimum detection limit of the system was 100 fg·μL⁻¹ for detecting fungal genomic DNA. This LAMP-based system provides a technique for specific detection of G. recalcitrans and rapid diagnosis of the disease it caused.

Phytophthora pathogens are responsible for causing disease in a range of environments, including natural, urban, nurseries and horticultural settings, and can be cryptically spread when present as inoculum in infected soil media. By evaluating the survival of Phytophthora inoculum in soil substrates without plants, their potential to be spread cryptically could be better understood. We tested the ability of Phytophthora multivora to survive in and be dispersed from sterile potting mix, forest soil and sand in the absence of plants when introduced as zoospores. We found that P. multivora zoospores readily encysted and survived in the potting mix for up to 76 days. The encysted zoospores were dispersed from the inoculated potting mix pots by overhead watering for up to 49 days. Zoospore cysts accumulated in the bottom sections of the potting mix pots as they were washed downward with each watering event. In contrast, P. multivora did not survive and persist in the sterile sand and forest soil substrates well. At 28 days-post-inoculation, only 10.1% of the destructively harvested replicates were positive with baiting for both sand and soil, while 100% of the potting mix reps were positive. The results raise concerns about the cryptic dispersal of inoculum during restoration projects especially from potting mix and show that zoospore cysts can contribute to the longer-term survival of Phytophthora inoculum. The potential presence of cryptic Phytophthora inoculum in nursery plants should be considered when sourcing plants for restoration projects to avoid inadvertently spreading soil-borne Phytophthora diseases.

All intracellular pathogens, including plant viruses, rely heavily on host cell organelles and metabolites for successful infection and multiplication. During infection, many viruses trigger changes in the host cellular structure, leading to the development of inclusion bodies that typically harbour viral structural and functional proteins. Identifying these inclusion bodies has become an essential diagnostic feature for specific viral infections. Viral inclusions form in various types, differing in location, size, contents, and potential functions. Viruses use these inclusion bodies to ‘house’ a complex mixture of proteins from both the virus and the host cell, aiding in virus replication, translation, and movement within and between cells. These aggregated structures may also serve to shield viral functional complexes from the host defence machinery responsible for viral degradation. This review provides comprehensive information on the existing and recent advances in the ultrastructural changes caused by plant viruses. These ultrastructural changes include the formation of viral inclusion bodies, modifications to the cell cytoskeleton components, endomembrane systems, and various cell organelles. Consequently, this review highlights the strategies used by viruses to replicate, hijack host cell machinery, and disseminate within plant cells.

This study reports the first occurrence of Schizophyllum commune causing wood rot and dieback in almond trees in Uzbekistan. Severe symptoms, including cankers, twig dieback, and extensive wood decay, were observed in a commercial orchard in Ortacirçik, Tashkent, affecting approximately 35% of the trees. The pathogen was isolated and identified using morphological and molecular techniques targeting ITS and LSU regions of rRNA, with pathogenicity confirmed through Koch’s postulates. This study underscores the need for integrated management strategies, including early detection and mitigation practices, to address the challenges posed by wood-decay pathogens and highlights the importance of further research on the epidemiology and resistance mechanisms of S. commune.

A. brassicae (Berk) Sacc. is an important necrotrophic fungal pathogen causing black leaf spot disease in crucifers. Seed can serve as a potential source of inoculum for the transmission of A. brassicae in mustard; however, silique -to-seed transmission of pathogen, the favoring environmental conditions along with the detection threshold for seed were not characterized empirically. So, the objectives of this study were to (i) determine the effect of environmental variables in disease appearance in field conditions in correlation with impact on yield, for this purpose mustard seeds were sown on different sowing date starting from 1st Oct to 19th Nov. at weekly interval; (ii) evaluate the effect of natural silique infection on silique-to-seed transmission of A. brassicae, for this purpose the seeds collected from naturally infected silique were analysed for pathogen recovery (iii) implications of the survival of A. brassicae in stored seeds at different temperature, for this purpose the collected mustard seeds were stored at varied temperature ranges; (iv) evaluate the detection threshold in stored seeds before next sowing season through PCR. The results indicate that development of Alternaria blight was favored by a mean maximum and minimum temperature between 29.0 and 20.9 °C and 11.3 to 6.9 °C respectively with an average relative humidity of more than 80% leading to earliest appearance of symptom in 98 days after sowing (DAS). A silique to seed transmission of approximately 42.6% was recorded for A. brassicae in the seeds collected from silique lot showing 65% disease severity. The stored seeds were monthly checked for pathogen recovery till six months and pathogen recovery of 19.6% and 13.8% was observed in stored seeds in Sep’24(before sowing) at 10ºC and 20ºC respectively while there was no recovery of pathogen in seeds stored at room temperature in Agar plate method. A specific fragment of ~ 400 bp was amplified by PCR using the specific primers and detection limit of 10gm seed at 30.00% silique infestation level and of 1gm at 65.00% silique infestation level was observed in stored seeds.

Rice production is threatened by various pathogens, including plant-parasitic nematodes like those from the genus Hirschmanniella, which can significantly reduce its yield. This study focuses on the morphological and molecular characterisations of Hirschmanniella mucronata associated with rice cultivation in Red River Delta in Vietnam. Morphological analysis revealed that while the three populations of H. mucronata from different regions exhibited some morphometric differences, their overall morphology was consistent with previous data. Morphometric variations were observed and confirmed by Cluster and MDS (Multidimensional Scaling) analyses, indicating possible regional or environmental influences on their morphology, emphasising the need for integrated approaches for accurate nematode identification. Molecular analyses based on D2–D3 of 28 S region identified three distinct clades within H. mucronata sequences. The Vietnamese sequences showed high identity (99.0–99.7% in 28 S and 99.88–99.97% for 18 S regions) to those from Cambodia. However, in 28 S tree, Chinese sequences (KR780066 and MW424471) displayed significant genetic divergence from all other sequences of H. mucronata, suggesting potential cryptic speciation or misidentification. The genetic diversity observed within H. mucronata underscores the complexity of its taxonomy and highlights the importance of using comprehensive identification methods. Additionally, our analysis showed that 18 S sequences of H. mucronata from Vietnam are 100% identical to each other and highly identical to those of H. mucronata available in GenBank (KP179330 and KP179332), differing by only 1–2 bp (99.88–99.97% identity). This study provides robust evidence for the presence of H. mucronata in Vietnam and calls for a reconsideration of previous identifications. This study also provided, for the first time, molecular data and SEM pictures of H. mucronata from Vietnam, facilitating the identification of this species.