Australasian Plant Pathology最新文献

Citrus tristeza virus (CTV; species Closterovirus tristezae) is ubiquitous in Australia, occurring in all production areas. Stem-pitting disease in white grapefruit varieties caused by CTV is managed by mild strain cross-protection. However, the protective isolate of CTV used for cross-protection, labelled PB61, is not fully characterised at the molecular level, even though most grapefruit budwood is inoculated with this virus isolate before release. In this study, we employed high throughput sequencing to assemble the 19,254 nucleotide-long genome of virus isolate PB61. Phylogenetic analysis revealed that PB61 belongs to the resistance-breaking (RB) genotype group first identified in New Zealand. PB61 is the first CTV isolate of any genotype from Australia to be sequenced in entirety, and the generation of this data provides a foundation for better understanding the mechanism of cross-protection in grapefruit.

During late 2020, tiny black spots were noticed (initially restricted to petiole part and later seen on leaves as well as young nuts) in WCT palms in coconut farm maintained at ICAR-CPCRI Research Centre Kidu, Karnataka. The tiny black spots later coalesce to form dark lesions with grey centre leading to drying of the entire infected coconut leaf. The disease later reemerged in the Kasaragod region of Kerala between 2022 and 2024, with a 68% incidence rate. A series of cultural, morphological, molecular characterization using multi-gene phylogeny, and pathogenicity assays with Koch’s postulates confirmed the association of Exserohilum rostratum as the causal organism of black spot disease. E. rostratum is known to be one among the causal agents responsible for leaf rot disease of coconut especially in Root (wilt) affected areas. To the best of our knowledge, this is the first confirmed report of Exserohilum rostratum as the primary causal agent of black spot disease in coconut. Given the pathogen’s broad host range and global distribution, its emergence as a distinct and independent coconut pathogen represents a potential transboundary risk to other coconut-growing regions. These findings highlight the evolving pathogenic potential of E. rostratum and underscore the need for international vigilance and integrated management strategies to safeguard coconut cultivation worldwide. Spraying with Hexaconazole 0.2% effectively controlled the disease under in vivo conditions, resulting in near-complete symptom reduction.

The 2022present study was conducted to evaluate the effectiveness of the combined application of Azadirachta indica (neem) and biocontrol agents against Meloidogyne javanica on peach. The results demonstrated that the combination of A. indica with Pochonia chlamydosporia remained superior by recording the lowest number of root galls, followed closely by Purpureocillium lilacinum, which was statistically at par with the chemical control (Rugby), showing gall reductions by 72.54%, 67.88%, and 75.65% over the control, respectively. Conversely, Trichoderma viride and T. harzianum were the least effective in reducing gall formation. The application of A. indica with biocontrol agents, especially P. chlamydosporia and P. lilacinum, also led to significant reductions in the number of egg masses. Moreover, the number of eggs per egg mass significantly decreased in these integrated treatments, with P. chlamydosporia recording the fewest eggs per egg mass, comparable to the Rugby treatment, while T. viride resulted in the highest fecundity. The overall nematode population was markedly reduced across all treatments (P < 0.05), with P. chlamydosporia causing the greatest suppression, followed by P. lilacinum. This study highlights the potential of A. indica in synergy with specific biocontrol agents, particularly P. chlamydosporia and P. lilacinum, for managing M. javanica in peach.

Flyspeck caused by Scleroramularia abundans and S. henanensis is reported on Actinidia sp. in New Zealand for the first time. Symptoms consisted of superficial specks on the surface of the fruit skin. The fungi were isolated and identified using ITS and Tef-1α sequencing. Modified Koch’s Postulates confirmed that these species were the cause of the observed symptoms. This is a new record of S. abundans and S. henanensis in New Zealand, and a new host association worldwide.

Fusarium species causes diseases of a diverse plant species. Though finger millets are resistance to a wide range of pathogens, sometimes, they are also attacked by various phytopathogens. During a survey in September, 2023, a serious leaf blight disease of finger millet (Eleusine coracana L.) was observed at agricultural fields of Morigaon district of Assam, India. The infected plant parts were collected from Morigaon district of Assam, during vegetative phase of the crop. The leaves displayed elliptical spots with grayish-white in centers and brown to reddish-brown margins. In severe cases, the affected leaves turned gray, the foliage withered, and the plants ultimately died. The pathogen was identified as Fusarium fujikuroi by morphological characteristics, pathogenicity test, molecular characteristics and phylogenetic analysis. This study reviles the first report of leaf blight in finger millet (Eleusine coracana L.).

Berkeleyomyces rouxiae is a highly destructive soil borne fungal pathogen causing a pandemic black root rot (BRR) disease of cotton seedlings in New South Wales, Australia. Accurate identification and differentiation of B. rouxiae from its morphological twin, B. basicola was solely based on DNA sequence analyses. In this study, we for the first time developed a duplex PCR assay for simultaneous detection and identification of B. rouxiae and B. basicola without the need for sequencing. Based on nucleotide variation in the MCM7 fragment, a new primer was designed to pair with the one developed by Nakane and Usami (2020) to specifically amplify a 159 bp amplicon of B. basicola. Subsequently, a duplex PCR assay was developed to simultaneously detect the two pathogens at a limit of an approximately 0.05 ng/µL. The duplex PCR was sensitive enough to detect B. rouxiae from crude extracts prepared from a 5-min-microwave-based DNA extraction protocol. Additionally, when used together with a nested PCR, the duplex PCR assay successfully detected the BRR pathogen in DNA extracts obtained directly from a small amount (15–30 mg) of diseased cotton tissue. This duplex PCR provides valuable diagnostic tool for detecting and monitoring the prevalence and distribution of BRR pathogens in cotton in Australia.