Australasian Plant Pathology最新文献

Plant-parasitic nematodes associated with dragon fruit have not previously been reported in Vietnam, nor has their impact on crop productivity been documented. In July 2023, a survey was conducted in dragon fruit orchards across southern Vietnam. A total of 60 soil and 60 root samples were collected from Tien Giang and Long An provinces. Plant-parasitic nematodes were identified from both soil and root samples, and notably, the cactus cyst nematode was detected in 100% of soil samples and 70% of root samples across all orchards. Morphological and molecular analyses confirmed the presence of the cactus cyst nematode, Cactodera cacti, representing a new record for Vietnam. Across the 60 orchards, 10 nematode genera were identified in soil and 5 genera in roots, including Cactodera cacti, Helicotylenchus sp., Tylenchorhynchus sp., Rotylenchulus sp., Tylenchus sp., Xiphinema sp., Basiria sp., Pratylenchus sp., Paratylenchus sp., and Criconemella sp. Identification of C. cacti was verified based on morphological traits and molecular data from the D2–D3 expansion segments of 28 S rDNA and the ITS region. In Tien Giang province, the average density of second-stage juveniles (J2) of C. cacti was 538 individuals per 500 g of soil and 20 individuals per 5 g of roots. In Long An province, the average density was 473 individuals per 500 g of soil and 41 individuals per 5 g of roots. This study provides the first report of C. cacti associated with dragon fruit in the Mekong Delta, Vietnam.

Begomoviruses constitute the largest genus in the family Geminiviridae and infect a wide range of plant species, including food, feed and fiber crops. According to the literature, these viruses were previously reported to infect multiple crops only in the warmer regions of Pakistan, with very little information available on their occurrence in the colder regions. However, between 2018 and 2021, typical symptoms of begomovirus infection were observed in multiple crops in Swat (a cold region), indicating possible begomovirus presence. The field surveys confirmed high disease severity in Tehsil Matta (75% infection). For molecular analysis, the symptomatic plants: Amaranthus retroflexus, Cannabis sativa, Capsicum annuum, Glycine max, Mentha longifolia and Parthenium hysterophorus along with healthy plants (controls) were collected and DNA was extracted. The extracted DNA was amplified to detect begomoviruses and their associated alphasatellites and betasatellites. The amplified products were cloned and Sanger sequenced. Complete genome sequencing of the begomoviruses and associated satellites showed the highest sequence identity with chili leaf curl virus (ChLCV), tomato leaf curl virus (ToLCuV), tomato leaf curl Karnataka virus (ToLCuKV), chili leaf curl betasatellite (ChLCuB), parthenium leaf curl alphasatellite (PLCuA) and papaya leaf curl betasatellite (PaLCuB). The identification of these multiple viruses indicates that begomoviruses are spreading to other crops as well as to colder regions. This is the first report of begomoviruses and their associated satellites infecting a diverse range of economically important plants in Swat, Pakistan. This study highlights the need for further research and the development of management strategies for begomovirus infections in the cooler regions of the country.

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.