Australasian Plant Pathology最新文献

Groundnut bud necrosis virus (GBNV), a plant virus belonging to the family Bunyaviridae and the genus Orthotospovirus, features a tripartite ambisense RNA genome. It primarily infects crops from the leguminosae and solanaceae families, causing distinctive symptoms such as chlorotic and necrotic spots. Present study aims to elucidate the effect of a few macro- and micro-nutrients supplementation on the progression of viral disease in cowpea plant. Study suggested that supplementation of macro-nutrients (P and K) and micro-nutrient (Zn) reduced viral accumulation and limits the viral spread in plant. Occurrence of oxidative stress and cell death by viral infection was judged by the increased concentration of ROS both at virus inoculated and systemic sites. Plants exhibited a decrease in ROS accumulation and cell death, supplemented with P, K and Zn than Mn supplemented and non-supplemented plants under viral infection. Antioxidant enzymes (CAT, SOD, GR and APX) activities were also increased in the plants supplemented with P, K and Zn than supplemented with Mn and non-supplemented plants. Expression levels of oxidative stress responsive miRNAs along with their corresponding target transcripts were also altered during nutrient supplementation in cowpea plants. Expression of miR319a.2, controlling metacaspase-8 (responsible for initiation of cell death) showed up-regulation, whereas miR398 and miR482 controlling COX-5b (responsible for mitochondrial ROS production) and NBS-LRR (responsible for disease resistance) genes, respectively showed down-regulation in the plants supplemented with P, K and Zn than the plants supplemented with Mn and non-supplemented. The study highlights the accumulation of ROS and PCD, along with the modulation of ROS and PCD-responsive genes during GBNV infection at both the inoculation and systemic sites, influenced by nutrient supplementation. The findings also discuss the potential of nutrient supplementation as a strategy to enhance viral resistance.

In November 2023, symptoms of leaf yellowing and wilting, as well as crown and root rot, were detected on raspberry plants in a commercial field located in Culiacán, Sinaloa, Mexico. Following the isolation of colonies displaying oomycete characteristics, two isolates were purified. Through a combination of morphological examinations, pathogenicity tests, and phylogenetic analysis using ITS and LSU sequence data, the causal agent was identified as Phytopythium helicoides Abad, De Cock, Bala, Robideau, Lodhi & Levesque. This is the first report of P. helicoides causing crown and root rot of raspberry worldwide.

Root-lesion nematodes, particularly Pratylenchus neglectus and P. crenatus (PNC), are widely distributed in New Zealand and cause significant damage to maize roots, reducing crop productivity. Despite their economic importance, no comprehensive assessment of commercial maize hybrids’ resistance to PNC has been conducted in the country. Significant variation was observed in the nematode reproduction factor (Rf) and final population (Pf) among hybrids. In Experiment 1 (initial population (Pi) = 1250 PNC kg⁻¹ soil), Rf ranged from 3.1 in hybrid P8500 to 7.1 in hybrid P9127, with Pf values ranging from 3863 to 8903 PNC kg⁻¹ soil + roots in 45 days. In Experiment 2 (Pi = 750 PNC kg⁻¹ soil), Rf ranged from 18.4 in hybrid P1613 to 37.5 in hybrid P8805, with Pf values from 13,784 to 28,426 PNC kg⁻¹ soil + roots in 60 days. These results indicate active nematode reproduction and substantial hybrid-dependent variation in host response. Experiment 3 examined the impact of varying initial inoculum densities (500, 1000 and 1500 PNC kg⁻¹ soil), showing a dose-dependent increase in Pf and corresponding root damage. Susceptible hybrid (P9127) exhibited up to 42% root dry weight and 22% shoot dry weight reductions. This study is the first systematic evaluation of PNC resistance in New Zealand maize hybrids. It identifies P9127 and P8805 as highly susceptible, and P0891, P8500, and P1613 as moderately resistant. These findings offer valuable benchmarks for future breeding and support nematode management in New Zealand.

Xanthomonas, comprising twenty-seven Gram-negative bacterial species, poses a significant threat to numerous plant species by causing severe diseases. Plasmids which are common components of phytopathogenic bacteria, play a crucial role in disease development as well as in the diverse evolution of their hosts. Plasmids carry virulence factors along with ecological variability which contributes in the pathogen's adaptation, through many traits acquired through horizontal transfer from other bacteria, thereby highlighting their vital role in rapid evolution. These plasmids are equipped with self-transmissible features and genes which are capable to encode a specific secretion system (Type IV). The "mobilome" of plant pathogenic bacterial plasmids encompasses particular insertion sequences and special transposable elements, which facilitate the intra and inter- transfer of genomic sequences. This review seeks to provide a comprehensive overview of the distribution, classification, transfer of plasmids, bacterial evolution, and the roles of plasmids in pathogenicity, antibiotic resistance, heavy metal resistance, and evolution associated with Xanthomonas.

Exobasidium vexans is an important tropical phytopathogenic fungus that causes blister blight in tea. Despite its devastating impact on tea cultivation, this pathogen remains poorly studied. In this study, fresh symptomatic leaf samples of blister blight were collected from the main tea-growing regions of Sri Lanka and from Northeast and Eastern India, where the disease was originally reported. Fresh collections obtained from each locality were characterized based on micromorphological characters and molecular data and an epitype was designated. A molecular phylogeny based on the ITS (ribosomal nuclear internal transcribed spacer 1, 5.8S, internal transcribed spacer 2), 28S rDNA (largest subunit of ribosomal gene partial sequence), and TEF-1α (translation elongation factor-1 alpha) revealed that E. vexans collections represent a monophyletic clade closely related to E. reticulatum. This study provides crucial insights into the phylogenetic position and genetic diversity of E. vexans, offering a foundation for future studies on its biology, epidemiology, and management to mitigate impact on global tea production.

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.