Australasian Plant Pathology最新文献

Salvia japonica essential oil (SJEO) is a natural active substance that has been widely used in medicine and food preservation. However, the antifungal mechanism of SJEO against plant pathogens is not well understood. This study examined the antifungal activity of SJEO against Fusarium oxysporum (F. oxysporum). The results demonstrated that SJEO significantly inhibits the mycelial growth and conidial germination of F. oxysporum in a dose-dependent manner. Scanning electron microscopy (SEM) confirmed that SJEO induces mycelial shrinkage, deformation, and rupture. Moreover, SJEO treatment substantially reduced the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), with decreases of 82.49%, 82.82%, and 58.38%, respectively, in the EC₅₀-treated group compared to the control group at 60 h. In contrast, the levels of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) were significantly elevated. SJEO also increased the permeability of the cell membranes of F. oxysporum, which led to the reduction of the cell contents. Additionally, SJEO at the EC₅₀ concentration significantly decreased the activities of endo-1,4-β-glucanase (EG), polygalacturonase (PG), and pectin lyase (PL) by 18.66%, 40.62%, and 80.19%, respectively, compared to the control group at 60 h. Blight in Pinus sylvestris var. mongolica was significantly reduced following SJEO treatment (p < 0.05). In summary, SJEO disrupts cellular redox balance and intensifies lipid peroxidation in cell membranes, leading to increased membrane permeability and ultimately cell death, and reduces the pathogenicity of F. oxysporum. These findings indicate that SJEO holds promise as a novel fungicide for controlling blight in Pinus sylvestris var. mongolica.

Stalk and bulb decay of garlic (Allium sativum L.) was observed in commercial fields in Jiroft County, Kerman Province, Iran. The causal agent was isolated from symptomatic plants and identified as Rahnella perminowiae based on its morphological and biochemical characteristics and confirmed by specific primers and sequence analysis of 16S rRNA, gyrB and atpD genes. The pathogenicity of the isolates was confirmed twice through inoculation experiments on garlic and onion leaves and bulbs, which resulted in the reproduction of symptoms and re-isolation of R. perminowiae. This is the first report of stalk and bulb decay of garlic caused by R. perminowiae.

During field surveys in 2022-23, phytoplasma diseases were a significant threat to the major flower crops of Andhra Pradesh, India, causing substantial economic losses. In this study, symptoms of phytoplasma were observed in three predominant flower crops of Andhra Pradesh: marigold, crossandra, and jasmine. Samples were collected from major flower growing areas of the state and subjected to PCR assays using universal P1/P7, R16F2n/R2 primers for amplification of the 16 S rRNA gene and gene-specific SecAfor2/Rev3 primers for amplification of a part of the secA gene. The 16 S rRNA gene sequence identity percentage based on Blast and in silico RFLP analysis of PCR-amplified phytoplasma 16 S rDNA was used to identify and classify them into sub-groups. The restriction profiles generated by digestion with 17 restriction endonucleases, showed that phytoplasma strains infecting marigold were highly uniform with members of ‘Candidatus Phytoplasma asteris’ (16SrI-B) and the phytoplasma strains infecting crossandra and jasmine were uniform with members of ‘Candidatus Phytoplasma australasiaticum’ (16SrII-D) subgroup. These phytoplasma strains were not previously reported to infect any flower crops in the state. Marigold, crossandra and jasmine are therefore considered new hosts for the 16SrI and 16SrII group phytoplasmas in Andhra Pradesh. In addition, this study also identified some new disease symptoms in marigold plants in addition to previously known ones.

Typical anthracnose symptoms were observed on leaves and fruit of achachairu (Garcinia humilis) in a producing region in Pernambuco, Brazil. The fungi were isolated from necrotic lesions on leaves and fruit to identify the causal agent and subjected to morphological and phylogenetic characterization. Based on these analyses, the species C. theobromicola and C. siamense were identified. The pathogenicity test confirmed that these two species are the causal agents of anthracnose on G. humilis. This is the first report of C. siamense and C. theobromicola causing anthracnose on leaves and fruits of G. humilis worldwide. Here, we also report these two species as pathogens on the fruit of G. brasiliensis (bacupari).

Okra (Abelmoschus esculentus) is an important vegetable crop of the Malvaceae, extensively grown in the Indian subcontinent. Okra enation leaf curl virus (OELCuV) has emerged as a significant threat to okra cultivation in India and is responsible for okra enation leaf curl disease (OELCuD) in India. This study aimed to investigate the cause and distribution of OELCuD in northern and southern India, focusing on Uttar Pradesh and Tamil Nadu. A survey conducted from 2020 to 2022 recorded OELCuD incidence of 17.37% in Meerut (Uttar Pradesh) and 63.3% in Viluppuram (Tamil Nadu). While this marks the first report of OELCuD in Meerut, its presence in Viluppuram indicates its continued spread. Symptomatic okra leaf samples were collected from both regions for molecular characterization to assess the disease's impact on okra production. The association of begomovirus with infected samples was confirmed through PCR with OELCuV coat protein gene- specific primers, which resulted in the expected amplicon (c. 770 bp).The full genome (DNA-A) was amplified by genome rolling circle amplification (RCA). The amplified RCA product was cloned, sequenced, and analyzed. The pairwise alignment and phylogenetic analysis revealed that the isolate from Viluppuram showed a maximum identity of 85.50% with GU112010 and 92.90% with MK084766 OELCuV isolates, while the Meerut isolate showed 92.60% identity with GU111996 and MK084765 isolates of OELCuV. Based on species demarcation criteria for begomoviruses, both the isolates are identified as new strain of Okra enation leaf curl virus and proposed the name Okra enation leaf curl virus [India: Meerut: Uttar Pradesh: 2023] and Okra enation leaf curl virus [India: Viluppuram: Tamil Nadu: 2023]. Further, recombination analysis revealed a single intra-specific recombination event in the genomic region in both the isolates understudy. This discovery is significant for understanding the spread of the OELCuD and provides valuable insights into the genetic diversity and recombination of the causal virus, particularly in regions where the OELCuV had not been previously reported.

Brown rot disease of Plum (Prunus salicina) was prevalent year-round, peaking in May, with symptoms of brown rot on plum fruits. The pathogen, isolated in May 2023–2024 in New Delhi, India, was identified as Lasiodiplodia pseudotheobromae through morphological and phylogenetic characterization. This is the first report of L.pseudotheobromae causing brown rot on Plum in India.

A novel species in the genus Closterovirus, family Closteroviridae, has been identified by high throughput sequencing in legume samples collected during plant pathogen surveys on Norfolk Island in 2014. The complete genome sequence of 16,815 nucleotides was obtained from a French bean (Phaseolus vulgaris) plant with symptoms of interveinal chlorosis in the older leaves. Complete or near complete coding sequences for the 10 open reading frames were also obtained from a second French bean plant, and batch samples of white clover (Trifolium repens) and pea (Pisum sativum). All isolates shared 99.7–99.9% nucleotide identity, indicating they are members of the same virus species.

During February-March 2022, farmers reported about the rapid drying and rotting of the crown, and eventual death of coconut (Cocos nucifera L.) palms in and around Kannur and Kasaragod districts of Kerala state, India. The symptoms included drying and drooping of leaves, sudden nut fall, and rotting followed by the toppling of the crown portion within a quick span of 2–3 months. Initial disease symptoms were observed as leaf blight starting from outer leaves. Diagnostic field survey was carried out in 12 different Panchayats experiencing crown rot disease, recording an average disease incidence of 9.5%. A series of cultural, morphological, and molecular characterizations using multi-gene phylogeny (ITS, tub2, tef-1α) and pathogenicity assays with Koch’s postulates confirmed the association of Neodeightonia phoenicum as the causal organism of crown rot disease. To the best of our knowledge, this study confirms the first report of crown rot disease in coconut caused by N. phoenicum. Root treatment with Hexaconazole was effective in controlling the disease under in vivo conditions, achieving 99% recovery.

One hundred and nine endophytic fungi were isolated from different S. glabra tissues at four locations, with a total isolation rate of 60.56%, belonging to 1 phylum, 2 classes, 9 orders, 21 genera and 28 species. Colletotrichum, Diaporthe and Phomopsis were the dominant genera and they accounted for 2.93, 12.84 and 10.09% of the total strains, respectively. The isolation frequency of Colletotrichum from Du 'an county was significantly higher than that from other locations (17.43%). The isolation frequencies of Colletotrichum and Diaporthe from the stems of S. glabra were the highest, at 19.27 and 8.26%, respectively, and these were significantly higher than for other tissues. Diversity and similarity analysis showed that the diversity, richness and evenness indexes from the different regions were highest from Guangxi, followed by Du 'an county. The leaf diversity index was the highest (1.26), while the stem richness and evenness indexes were the highest (4.32 and 0.49, respectively). The highest similarity coefficient of endophytic fungi among different regions was 55.32% in Du 'an and Jingxi counties. The root and stems had the highest similarity coefficient of 97.14%, indicating that species composition and diversity of endophytic fungi in the different regions and tissues of S. glabra were affected. In addition, the metabolites obtained from the crude extracts of the two endophytic fungi had the strong inhibitory effects on 11 pathogens. Phomopsis heveicola and Neofusicoccum parvum had the strongest inhibitory effects of Botrytis cinereal and Botrytis sp., with inhibitory rates of 100%.