Australasian Plant Pathology最新文献

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.

Cucumber (Cucumis sativus L.) is a vegetable widely grown worldwide for its agricultural, economic and nutritional value. With the increase in cucumber cultivation areas in recent years, soil-borne plant disease such as Pythium spp. and Fusarium wilt (FW) have caused significant economic losses for producers. Filamentous Trichoderma fungi and gamma radiation are well known for their ability to stimulate many plant-pathogen fungal interactions, plant defense mechanisms against these fungi (antagonistic, competitive, etc.), and plant growth. This study aims to examine the effects of Trichoderma spp. (Trichoderma harzianum and Trichoderma virens), which are among the sustainable practices against F. oxysporum f. sp. cucumerinum and P. aphanidermatum pathogens, and the effects of gamma rays (0, 50, 100, 150, 200, and 250 Gy), which are used as a reliable method for changing physiological and biochemical processes in plants and investigating their interactions with pathogens. The results revealed that the interaction between gamma rays and Trichoderma species increased the fresh and dry weights and shoot and root length values of the cucumber plants and decreased the disease severity. When Trichoderma harzianum (%51-%78 impact) and Trichoderma virens (%40-%67 impact) were compared, their effects on plant growth and disease severity were determined to vary according to parameters and gamma doses. These results indicate that gamma mutations may improve the biocontrol properties of T. harzianum and T. virens. According to the results of this study, gamma rays can be used in sustainable agricultural practices together with Trichoderma spp. as a bioformulation against pathogens that cause wilt and root rot in cucumber [F. oxysporum f. sp. cucumerinum (72%) and P. aphanidermatum (66%)] against.

Members of the genus Cilevirus are causative agents of citrus leprosis, an economically important disease of citrus in the Americas. Using high-throughput sequencing, we detected the hibiscus strain of citrus leprosis virus C2 (CiLV-C2H) infecting a cultivated Hoya macgillivrayi plant in Brisbane, Australia. The infection was not systemic, and presumably resulted from the feeding action of false spider mites (Brevipalpus spp.) that acquired the virus from an unidentified source of inoculum. Capsicum chlorosis virus, an orthotospovirus, was also present as a mixed infection, preventing the attribution of symptoms to CiLV-C2H.

Nematodes extracted from soil and infected root samples collected from soybean fields in southwest Ethiopia have revealed, for the first time, the presence of Pratylenchus goodeyi on soybean. Species identity was confirmed through morphological analysis (using light microscopy and scanning electron microscopy) and D2-D3 rDNA sequencing. A pathogenicity assay conducted under greenhouse conditions demonstrated that the tested soybean varieties are suitable hosts, with reproduction factor > 2 for P. goodeyi. Furthermore, the initial population density of P. goodeyi significantly affected the total fresh weight of the soybean plants, causing reduced plant height. Further research is necessary to assess its potential impact on soybean production at ranges of nematode densities and to develop effective management strategies.

Application of synthetic fungicides continues an essential approach for mitigating the harmful effects of Phakopsora pachyrhizi (Asian soybean rust, ASR). Nevertheless, the excessive use of these products causes decline of their efficacy and environmental pollution issues. Then, aiming to seek for alternatives on the control of ASR, the efficiency of using copper (Cu) in the form sparingly soluble microparticulate oxide (CuO) on protecting against the disease was compared to soluble sulfate (CuSO₄.5H₂O, CuS). The inoculation with urediniospores of Phakopsora pachyrhizi was performed 5 days after the spray with solutions containing 0.5 g L^− 1 of Cu for either sources or deionized water as a control (CT). Disease symptoms severity was assessed until 30 days after inoculation, when leaf tissue was sampled for studying mesophyll integrity. Further, in vitro tests were conducted to assess the impact of CuO and CuS on the germination of urediniospores; and, a complementary experiment evaluated the concentration of Cu in the sprayed leaves as function of the source. Results revealed that both tested compounds were capable of completely inhibiting urediniospores germination in vitro. However, CuO had greater efficiency to delay the onset of ASR symptoms and to reduce their severity, most likely because the treated leaves maintained greater Cu concentration than those receiving CuS. Moreover, Cu-sprayed leaves of inoculated soybean, regardless of the source, exhibited improved structural organization of the mesophyll compared to the CT. These findings suggest the potential of using CuO as an alternative to CuS for disease management programs with the aid of Cu-based products. Therefore, to refine the recommendations of sparingly soluble Cu sources, further studies remain crucial to reveal the mechanisms by which the protection against the disease is achieved.

Blackleg disease (Leptosphaeria maculans) impacts canola (Brassica napus) productivity worldwide, but the factors driving severity are not well defined. This study characterised blackleg disease progression from leaf lesion appearance to crown canker development. Leaf lesion severity at four crop growth stages and crown canker severity were empirically associated in crops planted at different times. The biotrophic growth rate of L. maculans in planta was determined at temperatures between 12 and 28 °C. Data from 24 Australian field experiments on spring B. napus cultivars were analysed to relate infection timing relative to crop growth stage and site conditions to crown canker severity at maturity. Despite variations in lesions across seasons and planting times, no significant relationship was found between lesion severity or incidence and crown canker severity. Crown canker severity increased significantly when younger plants were infected. The average in planta hyphal growth rate of L. maculans was 0.13 mm/°C-day. The analyses of biotrophic hyphal growth alongside the timing of infection were used to identify the onset of crown canker development. Simulations showed that thermal time and plant available water accounted for 61% and 36% of the variance in crown canker severity for moderately susceptible and moderately resistant genotypes, respectively. Blackleg crown canker severity is a nuanced interplay between time of infection relative to crop growth stage, genetic resistance, temperature, and moisture. Disease-crop models incorporating these factors could be used to explore how, for example, sowing time, level of host genetic resistance or extreme weather conditions affect disease infection and crop yield.