Australasian Plant Pathology最新文献

Commercially grown garlic is usually infected by complex mixtures of carla-, poty-, and allexiviruses. Specific detection of these viruses is difficult, particularly as some such as the allexiviruses exhibit serological cross-reactivity, and intraspecific nucleic acid sequence diversity is relatively large. While next generation sequencing shows much promise as a diagnostic method, it is not yet widely used for routine virus screening, especially in developing countries. The main objective of this study was to develop reverse transcription (RT)-PCR assays for each of the most common viruses associated with garlic. Primer specificity was examined in silico using sequences available on GenBank. The assays were then validated using virus isolates of known infection status, and application of the assays demonstrated by testing plants representing forty garlic cultivars grown in a major germplasm collection held at a government research station in South-east Queensland.

The Eucalyptus plantation industry in Indonesia has expanded rapidly during the last few decades. This growth is primarily attributed to the replacement of Acacia mangium, that was severely damaged by diseases. The rapid shift to large-scale monoculture plantations of Eucalyptus has introduced new challenges, particularly the emergence of new disease and pest problems. During routine Eucalyptus disease surveys in Indonesia, symptoms of a new leaf and shoot disease were observed on a single hybrid Eucalyptus grandis × pellita clone in Riau and Kalimantan. Leaf samples were collected, and isolations were made from the disease symptoms. Isolates were identified based on their morphological characteristics and DNA sequence data for seven loci. Phylogenetic analyses of the isolates revealed a novel species of Pseudoteratosphaeria, described here as Pseudoteratosphaeria supramediana sp. nov. A greenhouse pathogenicity test resulted in symptoms similar to those found under field conditions, and the inoculated fungus was consistently reisolated from the resulting lesions. Its appearance in two geographically distinct locations of Indonesia raises the possibility of multiple independent introductions of the pathogen.

Populus deltoides, an economically important and fast-growing tree species, was observed exhibiting severe foliar blight symptoms during disease surveys conducted recently in northern India. Fungal isolates consistently recovered from diseased leaf tissues displayed morphological characteristics typical of the genus Calonectria. Species identification was achieved using a polyphasic taxonomic approach integrating morphological characterization with multilocus phylogenetic analyses based on partial sequences of the actin (act), internal transcribed spacer (ITS), translation elongation factor 1-α (tef1), and β-tubulin (tub2) gene regions, which confirmed the pathogen as Calonectria pseudoreteaudii. Pathogenicity was demonstrated through detached-leaf assays as well as live-plant leaf inoculation experiments, both of which consistently reproduced disease symptoms comparable to those observed under natural field conditions. Re-isolation of the pathogen from inoculated tissues fulfilled Koch’s postulates. This study represents the first report of C. pseudoreteaudii causing leaf blight on P. deltoides in India and, to our knowledge, worldwide, thereby extending the known host range of this destructive pathogen.

Alfalfa (Medicago sativa) is the most important and high-yielding forage legume cultivated worldwide. The aerial parts of the plant play a crucial role in feeding livestock, and the roots contribute to soil nutrient levels, shape microbial communities, and support overall soil improvement. During our field survey of leaf-inhabiting fungi associated with this forage crop, we observed a widespread distribution of cladosporioid leaf spot symptoms in West Azerbaijan province, Iran. However, the causal agents associated with cladosporioid leaf spots and their pathogenicity in northwest Iran remain insufficiently resolved. Accordingly, this study aimed to identify the Cladosporium species associated with alfalfa leaf spot and assess their pathogenicity in this region. Samples with leaf spot symptoms were collected from various fields in West Azerbaijan province, including the cities of Miandoab, Mahabad, and Naghadeh, and then subjected to microscopic examination, resulting in the isolation of 49 Cladosporium isolates. A three-locus phylogenetic analysis (ITS, ACT and TEF1-α), combined with a detailed morphological examination of representative isolates, confirmed the association of six Cladosporium species with alfalfa leaf spot in Iran: C. asperulatum, C. cladosporioides, C. limoniforme, C. macrocarpum, C. submersum, and C. tenellum. Among these, C. asperulatum and C. submersum are new records for the funga of Iran. In addition, C. asperulatum, C. limoniforme, C. macrocarpum, C. submersum, and C. tenellum are reported for the first time on M. sativa in the world. Pathogenicity tests under greenhouse conditions confirmed that four species, including C. asperulatum, C. limoniforme, C. macrocarpum, and C. submersum, were pathogenic on alfalfa leaves. These findings clarify the species complex involved in alfalfa leaf spot in northwest Iran and provide an initial evidence base for disease management, with the potential to reduce economic losses.

During the Kharif seasons of 2023–24 and 2024–25, leaf blight and stem rot symptoms were observed on mungbean (Vigna radiata) at Research Farm, ICAR-IIPR, Kanpur, India. Symptoms began as water-soaked lesions on leaf margins and stunted growth, progressing to necrotic stem and pod lesions. The causal pathogen was identified as Pythium catenulatum based on symptomatology, pathogenicity, and ITS-based molecular analysis. This is the first report of P. catenulatum causing stem rot in mungbean in India.

Plant extracts are emerging as alternative control strategies against root-knot nematodes (RKN) due to limitations of conventional methods. The nematicidal activity of hot and cold aqueous extracts of Ricinus communis was evaluated against Meloidogyne incognita under both in vitro and in vivo conditions. The nematicidal efficacy of hot and cold aqueous extracts was assessed on second-stage juveniles (J2s) of M. incognita at concentrations (0.5, 1, 2.5, 5, 25, 50, 75, and 100%) applied in vitro. The results of the Petri experiments indicated that the hot aqueous extract did not affect M. incognita at 0.5, 1, 2.5, and 5% concentrations, while the cold aqueous extract exhibited a high suppressive effect after 72 h. Above 25% concentrations of cold aqueous extracts were observed 100% mortality of nematodes in 24 h. After 24 h of exposure of M. incognita eggs to the cold aqueous extracts recorded egg hatch inhibition of 100%. Pot experiments were carried out using two separate methodologies (covered and uncovered) and four doses (25, 50, 75 and 100% cold extracts) that showed the highest effect in Petri experiments. Pot experiments demonstrated that both methods exhibited a pronounced suppressive effect on M. incognita, commencing at the 25% concentration. Consequently, the study has demonstrated the potential efficacy of cold aqueous extracts derived from R. communis seeds in management M. incognita.

Fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae) is an invasive and important pest of multiple crops including grains and vegetables. The moth was first detected in Australia in 2020 and has since established populations across the north of the continent with further spread expected. Surveys for parasites and pathogens impacting Australian fall armyworm populations were undertaken between 2020 and 2025. Here, we report on two distinct genetic lineages of parasitic nematode of the family Mermithidae collected from S. frugiperda caterpillars during this period. Because the specimens available were post-parasitic juveniles, they could not be reliably identified morphologically beyond the family level. Phylogenetic analyses using two ribosomal (18S, 28S) and one mitochondrial (COI) gene demonstrated the presence of two distinct species-level lineages (one in Queensland and one in the Northern Territory) but they did not resolve the taxonomic position of either. Thus, neither lineage can be reliably assigned to any known genus and are therefore given informal placeholder assignments: Mermithidae sp. FA-QLD and Mermithidae sp. FA-NT. Mermithid nematodes likely represent an important component of natural population regulation for fall armyworm and join a growing list of organisms which have been found parasitising this moth in Australia.

Severe phyllody and little leaf symptoms were observed on roses and Cleome viscosa plants in the nurseries of Andhra Pradesh, India. Nested PCR assay for amplifyingphytoplasma DNA, Phylogenetic and virtual RFLP analysis were performed to confirm the presence and identify the associated phytoplasma. The results specified the presence of phytoplasma on two commercial rose varieties and in the alternate host and confirmed “Candidatus Phytoplasma australasiaticum (16SrII-D)” strain as the causal agent in both diseased rose cultivars and the alternate host. This is the first report and identification of phytoplasma infecting roses in Andhra Pradesh.