Australasian Plant Pathology最新文献

Cassava is a vital starch food for the global population, primarily cultivated by smallholder farmers on less than one hectare of land. Cassava mosaic disease (CMD) poses a potential threat, causing yield losses of 50–70 per cent. Various causal agents of CMD have been identified in different regions. To curb CMD menace, farmers and researchers employ strategies such as using disease-free planting materials, resistant varieties, nutrient management, and integrated pest and disease management practices. In India, the threat of CMD in cassava production is increasing. This article reviews the past studies on CMD, including its symptoms, yield losses, spread, nutritional management, and control, to provide a comprehensive understanding of the disease and its management.

Coffee (Coffee arabica L.) is an economically valuable crop grown worldwide. In 2022, sooty mold symptoms were noticed on coffee leaves in a greenhouse in Namwon, Korea. The presence of this mold can potentially hinder this crop's photosynthesis and growth. The fungus responsible was identified as Leptoxyphium fumago based on morphological characteristics and molecular phylogenetic analysis of ITS, LSU, and EF1-α sequences. Artificial inoculation of a conidial suspension to coffee plants validated its pathogenicity. This is the first global report of L. fumago causing sooty mold on coffee plants.

Black root rot (BRR) caused by a soilborne Berkeleyomyces rouxiae is a pandemic disease on cotton seedlings in Australia. BRR of cotton was reported for the first time in northern New South Wales (NSW), Australia in 1990. Now, the disease is widespread across cotton growing regions in NSW. Much research has focused exclusively on control management; however, relatively little work has been conducted to understand the BRR pathogen population for their temporal and spatial distributions. A total of 294 B. rouxiae isolates that were freshly collected across NSW over five cropping seasons (2017–2022) were assessed for their genetic diversity based on sequences of the nuclear ribosomal DNA internal transcribed spacer, mini-chromosome maintenance complex component 7, translation elongation factor 1-alpha and RNA polymerase II second largest subunit. Additionally, these isolates were subjected to a specific duplex PCR assay for mating type determinations. Multiple sequence alignments revealed that the prevailing cotton-B. rouxiae was 100% identical; however, the population can be divided into two subgroups based on the presence of mating idiomorphs. The MAT1-1 type was predominant and accounted for 62.2% of the population. A total of 25/77 fields were confirmed to harbour both MAT1-1 and MAT1-2 isolates. However, we failed observe sexual structures in crossing experiments. Based on the sequence uniformity of the cotton-B. rouxiae population, we suggest that the pathogen has spread from one field to another. Therefore, stricter farm hygiene practices should be enforced to minimise a further spreading risk.

A beneficial technique for the detection of missing 5’ and 3’ ends of the genome is RACE (Rapid Amplification of cDNA Ends). Subsequently the Squash mosaic virus has an important role in the quality and quantity of cucurbits crops and considering that it was not possible to trace the Iranian isolate of this virus with the primers designed based on the sequence of other SqMV isolates, therefore, by using the RACE method, the initial part of the genome of Iranian isolate of SqMV was identified. The results showed that the Iranian SqMV isolate has a different genomic beginning than other isolates worldwide. Therefore it can be suggested that the RACE technique can be valuable for recognizing different ends in the genome.

Pathogenesis-related (PR) proteins are a large class of proteins that accumulate in plant cells in response to multiple biotic and abiotic stresses. Root rot is an important disease of the perennial medicinal plant Panax notoginseng, with Ilyonectria destructans identified as one of the causative pathogens. However, little is known about the PR-encoding genes expressed during the infection of P. notoginseng by I. destructans. In this study, we isolated a PR4 gene from P. notoginseng(PnPR4) on the basis of a genomic analysis. The expression of this gene was significantly up-regulated in the roots of I. destructans-infected P. notoginseng plants at 72 h post-inoculation (relative to the control level). The expression of PnPR4 was affected by hydrogen peroxide, gibberellic acid, ethephon, abscisic acid, and salicylic acid. The transient expression of the PnPR4-GFP fusion gene in tobacco epidermal cells indicated that PnPR4 was localized in the cell wall (i.e., extracellular protein). In addition, the purified PnPR4 recombinant protein had antifungal activities, with inhibitory effects on I. destructans. Furthermore, the PnPR4 gene was transferred into the model plant tobacco to verify its function. The overexpression of PnPR4 increased the resistance to I. destructans. In conclusion, PnPR4 contributes to the defense response of P. notoginseng to I. destructans.

Stem rot disease, caused by Sclerotium rolfsii Sacc., is a major impediment to groundnut production in Asia, sub-Saharan Africa and the Americas. The present study focused on identifying potential sources of resistance by screening a set of groundnut advanced breeding lines in laboratory, glasshouse, and field conditions. Two experiments in a glasshouse and a field were conducted during the rainy seasons of 2022 and 2023 at ICRISAT, India. Disease incidence was recorded at 15, 30, 45, and 60 days after inoculation. The results identified five lines–ICGV 171025, ICGV 181035, ICGV 181458, ICGV 211107, and ICGV 171002–as moderately resistant, with less than 30% incidence. The remaining lines were susceptible, with more than 30% incidence in both field and glasshouse experiments. In the laboratory experiment, the response to oxalic acid assay was conducted using detached stems (laterals and mains), and the results revealed differential reaction after immersing in 0-, 20- and 50-mM oxalic acid, and the response was recorded at 12-, 18-, and 24-hours intervals. Significant wilt symptoms were observed at 24 h for laterals and mains in 20mM oxalic acid concentration, whereas in 50mM concentration wilting was exhibited at 18-hour intervals for laterals and 18 to 24-hour intervals for main stems when compared to control. Four lines–ICGV 171025, ICGV 181035, ICGV 171002, and ICGV 211107–were reconfirmed as moderately resistant through this assay, consistent with field and glasshouse findings.

The Crown Daisy flowers showing typical phyllody and virescence symptoms were observed in Pune, Maharashtra, India. The total genomic DNA was extracted from the symptomatic plants which was used for amplifying the 16S rRNA region. The nested PCR amplification using universal phytoplasma primers confirmed the phytoplasma presence which was further confirmed upon sequencing which revealed 100% identity with ‘Candidatus Phytoplasma asteris’ 16SrI-B phytoplasmas. Further the virtual RFLP analysis of 16S rRNA gene sequence of F2n/R2 region (1.2 kb) showed a similarity coefficient of 1.00 with 16SrI-B subgroup phytoplasma.

In 2023, a severe outbreak led to a 70% mortality rate among Cyclamen persicum plants in Holambra, São Paulo, prompting an investigation to identify the causal agent. Symptomatic plants were sampled, and the fungus, designated CMAA 1919, was isolated and identified through morphological analysis. Pathogenicity was verified via Koch’s postulates, with inoculated plants replicating wilt symptoms. To support genomic characterization of the pathogen, whole-genome sequencing was conducted using the Illumina platform. Genomic DNA was extracted, sequenced, and processed, resulting in a 48.9 Mb genome with 200x coverage and 97.5% completeness. Phylogenetic analysis positioned CMAA 1919 within a Fusarium cluster, confirming its closest relation to Fusarium oxysporum strain Fo47 (99.07% genomic similarity) and other pathogenic strains. This study presents the first genomic and morphological description of Fusarium oxysporum f. sp. cyclaminis (CMAA 1919), the causative agent of Fusarium wilt in cyclamen in Brazil.

Pennisetum × sinese Roxb is a critical forage crop widely cultivated in Yunnan Province, China. During a 2023 field survey in Lijiang City, Yunnan, five Pennisetum × sinese Roxb plants exhibiting lodging and disintegration of internal stalk tissues were examined to determine the causal agent. Through isolation, morphological characterization and sequence-based identification, Bisifusarium delphinoides (Schroers, Summerb., O'Donnell & Lampr.) was isolated and confirmed as the causative pathogen from the symptomatic Pennisetum × sinese Roxb plants. Pathogenicity tests and the fulfillment of Koch's postulates demonstrated that B. delphinoides is the agent responsible for the observed stalk rot disease in Pennisetum × sinese Roxb. To the best of our knowledge, this is the first report of B. delphinoides causing stalk rot in Pennisetum × sinese Roxb. The emergence of this disease poses a serious threat to the production of this important forage crop in the region.

Anthracnose decay symptoms were observed on mature blueberry fruit sampled from retailers in Manawatū, New Zealand. To identify the causal agent, fungi were isolated from fruit lesions and initially subjected to morphological and phylogenetic characterisation. Based on these analyses, two species of the Colletotrichum genus, Colletotrichum fioriniae and Colletotrichum godetiae, were identified. Pathogenicity tests subsequently confirmed that these two species were responsible for causing the observed symptoms. This is the first report of Colletotrichum fioriniae and Colletotrichum godetiae causing anthracnose disease on mature blueberry fruit in New Zealand.