Australasian Plant Pathology最新文献

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%.

Cananga odorata essential oil (COEO) from Cananga odorata has medical uses but its antifungal against plant phytopathogenic fungi was unknown. In this study, COEO showed significant concentration-dependent inhibition of mycelial growth and spore germination in Pestalotiopsis neglecta (P. neglecta). Compared with the control groups, the contents of ergosterol and total lipids in P. neglecta decreased by 50.08% and 83.30% respectively after being treated with 0.516 µL/mL (EC₃₀) and 0.797 µL/mL (EC₅₀) of COEO. Subsequently, an overall upward trend was observed in the activity of superoxide dismutase (SOD), while downward trends appeared in the activities of catalase (CAT) and peroxidase (POD). Meanwhile, the contents of hydrogen peroxide (H₂O₂) and Malondialdehyde (MDA) increased. These alterations induced oxidative stress and aggravated the peroxidation state of cellular membrane lipids. Furthermore, the treatment of COEO was found to enhance the extracellular conductivity and the content of extracellular soluble protein in P. neglecta. The staining with Propidium iodide (PI) and Fluorescein diacetate (FDA) demonstrated that COEO induced the disruption of cell membrane integrity. Moreover, the activities of polygalacturonase (PG), pectin lyase (PL), and endoglucanase (EG) were observed to decrease in the control groups. In vivo, 120 µL/mL COEO inhibited black spot needle blight in Pinus sylvestris var. mongolica. COEO alters cell membrane, triggers stress, and affects P. neglecta growth and virulence, showing potential as a plant-derived pesticide for controlling this and other plant diseases.

Brown spot, one of the emerging diseases affecting rice production worldwide, has been studied for over a century. A quick and reliable PCR-based diagnostic assay has been developed to detect the causal organism of brown spot disease, Bipolaris oryzae for its rapid monitoring in rice-grown areas. In this study, we designed a set of primers (ssp1RABo-F and ssp1RABo-R) from a hypothetical small-secreted protein (SSP) gene, unique to B. oryzae (XM_007689836.1) that was identified through comparative secretome analysis. This specific marker (ssp1BoRA_278, KU900505.1) amplified a sequence of 278 bp in all the isolates of B. oryzae tested during the study. This novel marker distinguished B. oryzae from other Bipolaris spp. as well as from other fungal pathogens of rice and other crops. The analytical sensitivity of the marker was observed as 1 pg (copy no. 27.91) using conventional PCR assay. To enhance the sensitivity and utility of the marker, a real-time PCR-based (qPCR) assay was also developed using the same primer set as used in conventional PCR. The sensitivity of the marker was enhanced by 10 times to detect as less as 100 fg DNA (copy no. 2.791) of the pathogen through qPCR. The PCR and qPCR-based detection using this marker will provide a rapid and reliable technique for quick and efficient detection, quantification for genotype resistance, and monitoring of B. oryzae in field, seed, and soil. The marker could detect the pathogen in the host before the appearance of the symptoms. Therefore, early detection using this marker will help in better management of brown spot disease of rice.

Leaf spot disease of Aloe vera (Aloe barbadensis Mill.) was prevalent year-round, peaking in February, with symptoms of reddish-brown to dark-brown sunken spots on leaves. The pathogen, isolated in February 2022–2023 in Kalyani, West Bengal, was identified as Colletotrichum siamense through morphological and phylogenetic characterisation. This is the first report of C. siamense causing leaf spot on Aloe vera in India.

The scarcity of arable water is a worldwide challenge. Charcoal rot is an important disease for sunflower plants, a crucial oil crop in Egypt and globally. Field experiments were conducted in Ismailia Governorate, Egypt during the 2020 and 2021 growing seasons in soil naturally infested with Macrophomina phaseolina to study the effect of water source and irrigation systems on charcoal rot development on sunflower plants. River Nil (non-sodic containing 0.84 meq sodium/ L), deep-well (sodic containing 59 meq sodium/L), and surface and drip irrigation were used. The incidence of charcoal rot was increased under well water and drip irrigation more than river water or surface irrigation. Infection increased from 27.5 to 27.3% with river water via surface irrigation to 37.4 and 38.2% with well water via drip irrigation in the first and second seasons respectively. Nitrogen concentration in sunflower leaves was not influenced by water source or irrigation system, while P and K decreased from15.1, 15.4, 24.3 and 24 mg/ gm with river water to13.1, 13.5, 13.3 and 14.3 mg/ gm with well water when surface irrigation used in the first and second season. Seed yield and oil concentration decreased from 43.1 to 44.7 kg seed/ plot; and 57.4 and 47.5% seed oil with river water to 37.4 and 35.8 kg seed/ plot; and 43.6 and 38.2% seed oil with well water via surface irrigation in first and second season.Well water increased sodium accumulation in the soil compared to river water from 1.49 to 1.74 kg/ hectare. Irrigation system did not affect sodium content when river water used, while with well water, drip irrigation increased sodium content more than surface irrigation. Consequently, water quality and irrigation systems affect sunflower plants’ growth, charcoal rot incidence, and may increase sodium accumulation in soil.

Marker-assisted backcross (MABC) breeding technique was employed to introgress the Quantitative Trait Loci (QTL) regions for the bruchid resistance and Mungbean Yellow Mosaic Virus (MYMV) disease resistance from resistant donor TU 68 into the popular blackgram variety MDU 1. Bruchid pest and MYMV disease is the major pest and disease of blackgram that renders the crop growth and yield under severe epiphytotic conditions. Foreground selection was performed using six markers namely, CEDG 020, CEDG 067 in LG 5, CEDG 302, GMES 1248 in LG 8 and CEDG 180, CEDG 116 in LG 10 linked with bruchid pest and MYMV disease resistance. In addition, 40 Simple Sequence Repeats (SSR) markers found polymorphic among the MDU 1 × TU 68 population were used in background selection. Among the background introgressed lines (BILs), recurrent parent genome recovery ranged from 64.8 to 72.4%. Among these introgressed lines viz., BIL-95-5, BIL-95-3, BIL-95-1, BIL-135-5, BIL-33-2, BIL-20-3, BIL-20-1, BIL-135-2, and BIL-95-2 showed superior yield performance than the recurrent parent MDU 1. All the introgression lines exhibited significant resistance to bruchid and MYMV disease. Hence, these lines can be further advanced to large-scale trials to evaluate yield parameters, bruchid resistance, and MYMV disease resistance to release as a new improved variety.