Australasian Plant Pathology最新文献

Austropuccinia psidii causes rust disease on species within the family Myrtaceae. It was first detected in Australia in 2010, with the first detection in Western Australia in 2022. While species within the genus Melaleuca from eastern Australia show variable responses to the pathogen, little is known of the response of species from Western Australia. This study established that 13 previously unscreened species of Melaleuca, including Threatened and Priority listed species that were grown from seeds sourced from Western Australian populations, were susceptible four months post-germination to the pandemic strain of the pathogen. The proportion of highly susceptible plants within a single species ranged from 2 to 94%, with several species displaying highly variable levels of resistance to A. psidii. These results highlight the importance of disease screening and may direct conservation efforts.

Anthracnose caused by Colletotrichum species is an important disease of mango (Mangifera indica L.) affecting leaf, flowers and fruits in mango orchards worldwide. The fungus Colletotrichum sp. usually invade the fruits during its developmental stage but remains quiescent until fruit ripening culminating in devastating anthracnose disease, especially during post-harvest stage. In contrary, new kind of pre-harvest anthracnose symptoms were observed on green unripe mangoes with varying level of incidence at field level in the state of Odisha, situated in Eastern India. This study attempted to characterize the Colletotrichum species affecting mango cultivars and causing new kind of symptoms under field condition on maturing green mangoes in comparison to post-harvest phase using morphological methods and molecular tools as well as by pathogenicity tests on intact green as well as on detached mature fruits. Eight Colletotrichum isolates from pre-harvest phase and two from post-harvest phase isolated from different mango varieties were studied for their diversity through morphological examination as well as sequence analysis of internal transcribed spacer (ITS), chitin synthase (CHS-1), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), β-tubulin (TUB2) and ApMat genomic regions. Multigene phylogeny of all ten isolates revealed the identification of C. siamense. Pathogenicity assay of all 10 Colletotrichum isolates on green intact fruits in field as well as on detached ripening fruits in laboratory resulted in similar anthracnose symptoms on two selected test varieties Arka Anmol and Mallika. Results confirmed the association of C. siamense with both pre as well as post-harvest anthracnose symptoms of mango. Accurate pathogen identification provides a reliable basis for devising disease management schedules against anthracnose occurring at different phenological stages of the mangoes.

Abstract

Urad bean (Vigna mungo L.), commonly known as black gram, is an important pulse crop in Indian agriculture. However, the crop confronts significant challenges due to diseases, including pod rot caused by Fusarium sp, and pest attacks by the pod bug (Clavigralla gibbosa). Accurate prediction of disease severity and pest incidence is essential for formulating effective management strategies to ensure sustainable crop production. A comprehensive field experiment was conducted at the Crop Research Center, Pantnagar, Uttarakhand, during the rainy seasons of 2021 and 2022. The primary objective was to analyze the behavioral patterns of disease severity and pod bug infestations in urad bean. Data on pod rot disease severity and pest incidence were meticulously recorded on a weekly basis. Four Machine Learning approaches, namely ANN, Lasso, Ridge, and Random Forest, were trained and tested to understand the influence of meteorological parameters on pod rot and pest severity. The Random Forest model exhibited superior generalization performance in predicting both disease severity and pest incidence, closely followed by Ridge regression and Lasso regression. The ANN model showed slightly higher testing error metrics. Notably, the Random Forest model demonstrated effective control overfitting, yielding maximum R-squared values of 0.70 and 0.82 for pod rot and pest incidence, respectively. The study’s findings offer valuable insights for agricultural stakeholders in selecting appropriate prediction models to optimize crop management practices and promote sustainable agriculture.

Wheat stripe/yellow rust (WYR), caused by Puccinia striiformis f. sp. tritici (Pst), is a major constraint in global wheat production. A set of 766 hexaploid synthetic wheat lines, including primary crosses of Triticum turgidum x Aegilops tauschii and their derivatives, were screened in artificially rust inoculated field nurseries for three seasons. From this set, a core set of 94 non-lodging lines with unique pedigrees and resistance to Pst that was consistent across years was established. The core set was tested for adult plant field response under field conditions for three seasons in Australia and at least one crop season in Ethiopia, India, Kenya, Nepal and Pakistan. It was also challenged with an array of well-defined Pst pathotypes at seedling growth stages in the greenhouse, and genotyped with molecular markers linked to the adult plant resistance (APR) genes Yr18, Yr36 and Yr46. Combined analysis of field rust responses, multi-pathotype seedling phenotyping and marker genotyping resolved seven classes of Pst resistance: uncatalogued (new) APR (UAPR, 11%), uncatalogued seedling resistance (USR, 46%), known seedling resistance (KSR, 5%), KSR + USR (2%), Yr18 + UAPR (4%), Yr18 + USR (29%) and Yr18 + KSR (3%). A majority of the lines carrying UAPR and USR either singly or in combination showed high levels of field resistance across all field sites and years of testing, demonstrating that these lines represent a valuable resource for breeding wheat for resistance to Pst.

Early blight (EB), caused by the dominant species Alternaria alternata, is a major global disease of tomato (Solanum lycopersicum L.; Solanaceae) reducing the vegetative organs and causing losses. Sustainable food production mainly depends on the rational use of chemical fertilizers and fungicides in integrated plant disease management. Hence, the fungicidal activity of ortivatop^® (azoxystrobin + difenoconazole), Signum WG 33.4% (pyraclostrobin + boscalid) and daconyl SC 72% (chlorothalonyl) was evaluated against tomato EB disease under field conditions. Two experiments were conducted during the cropping seasons from 2019 to 2020 in three regions. The experimental design was a randomized block with 4 replications using Ortivatop^® (ORT) at three doses of -900, -1100 and -1300 ml. ha⁻¹ (recommended doses of the company), daconyl (DAC) 2 l. ha⁻¹ and Signum (SIG) 0.5 l. ha⁻¹. The findings showed that ORT-1300 (20.6%) and DAC (22.7%) resulted in the lowest EB disease severity, followed by SIG (25.7%), ORT-1100 (26.9%) and ORT-900 (31.7), in contrast to 59.1% of the control. Compared with treatment without fungicide, all fungicides reduced the AUDPC (area under disease progress curve) and provided an increase in productivity. ORT-1300 ml ha⁻¹ showed the greatest reduction in AUDPC by up to 70% and increased tomato yield by threefold more than the untreated control. Therefore, the current study suggests that foliar spraying with ORT-1300 ml. ha⁻¹ at all three growth stages, is an ideal solution for EB disease management.

The Canary Island date palm (Phoenix canariensis) is one of the most representative tree species of the urban landscape of México City. However, since the last decade, severe foliar damage and decay has been observed, causing the death of hundreds of individuals in different boroughs of the city’s north zone. The symptoms observed in these affected palms were indicative of Texas Phoenix palm decline (TPPD), a serious disease associated with phytoplasmas of the 16SrIV-D subgroup. In this study, the use of nested-PCR and real-time PCR detected the presence of phytoplasmas of group 16SrIV in 21 out of 25 Canary Island date palms located in the Miguel Hidalgo, Benito Juárez, and Cuauhtémoc boroughs of México City. Sequencing the F2nR2 fragment of the 16S rRNA gene generated from the phytoplasma DNA samples of six positive palms, and subsequent in silico analysis, revealed that these phytoplasmas belonged to the 16SrIV-D subgroup. The presence of this phytoplasma strain in México City extends the range of known climates in which this pathogen and its vectors are capable of subsisting, in addition to evidencing an increase in the geographical distribution of this pathogen in recent years.

Cirsium arvense is an important weed in temperate areas, causing yield losses in pasture and cropping systems. Endophytes may affect fungal biocontrol agents deployed to control C. arvense. This was the first study sampling leaves, stems, and roots of C. arvense multiple times in one growing season to determine which endophytic genera were associated with this plant species. Eighty-eight endophytic genera were isolated by culture methods and identified with molecular markers. Sixty-five of these have not previously been reported for C. arvense. This study was the first to document many genera belonging to the orders Pleosporales, Hypocreales, and Diaporthales that have not previously been identified in association with C. arvense. In addition, this study isolated more Leotiomycetes and Helothiales than previous studies on C. arvense endophytes. Information on endophytic genera in C. arvense will aid our understanding of biotic factors influencing fungal biocontrol agents and may improve effectiveness of biocontrol agents.

In Brazil, the cultivation of macadamia (Macadamia integrifolia) has expanded within the nut industry. However, there is a lack of information concerning the primary macadamia diseases under Brazilian conditions, which is crucial to defining management strategies. This study aims to identify the causal agents responsible for macadamia diseases and determine their prevalence based on a 2-year survey in a representative production area in Brazil. Samples were collected from leaves, trunk sections, racemes, and macadamia fruit from November 2019 to September 2021 in Brazil. All associated microorganisms were isolated, and pathogenicity tests were conducted to fulfill Koch’s postulates. For isolates confirmed as pathogenic, morphological characterisation and molecular identification were performed. The diseases observed, along with their respective prevalence, were as follows: leaf spot caused by Neopestalotiopsis (7%), stem canker caused by Lasiodiplodia (28%), Cladosporium blight caused by Cladosporium (72%), and fruit rot caused by Colletotrichum (18%). This study marks the first reporting of the fungi species L. pseudotheobromae, C. xanthochromaticum, and Co. siamense as phytopathogens of macadamia in Brazil. Additionally, it reports C. xanthochromaticum and Co. siamense for the first time as causal agents of Cladosporium blight and fruit rot in macadamia worldwide, respectively.

In this study, we evaluated the effectiveness of thermotherapy in eliminating apple rubbery wood virus 2 (ARWV-2) in six infected apple varieties collected from regions in China. These plants were subjected to high-temperature treatment, followed by excision of shoot tips, which were subsequently grafted onto the rootstock. All varieties exhibited high thermostability, but the survival rates (average: 30.5%) of the shoot tips varied markedly. The regenerated plants were tested using semi-nested PCR; the results showed that the ARWV-2 elimination efficiencies differed greatly among the varieties. The elimination rates were > 80% for Baxianzaofu and Ruixue and < 50% for HL, Longkou no. 3, and Yishuihong. Notably, all surviving Longkou no. 3 plants remained infected with ARWV-2. The average ARWV-2 elimination efficiency was 44.3%, closely aligning with that of the apple stem pitting virus and apple stem grooving virus. This suggests that the presence of ARWV-2 may influence the ability of certain varieties to yield virus-free germplasm. Moreover, analysis of the ARWV-2 sequences from Baxianzaofu, Ruixue, Longkou no. 3, and Yishuihong revealed that the elimination rate exhibited minimal correlation with the virus diversity. The consistency and identity of the different variants within the same isolates or among the four isolates were high. Our findings can serve as a valuable foundation for developing treatment strategies to address ARWV-2 infections.

Species of Neodolichodorus are plant-ectoparasitic nematodes, belonging to the family Dolichodoridae, occurring mainly in sandy soils. Fourteen species have been reported within this genus, each exhibiting unique morphological features aiding identification. In this study, we describe a new nematode species, Neodolichodorus bachlongviensis sp. n., which exhibits close morphological similarities to N. obtusus, N. adelaidensis, N. arelairius, and N. hainanensis in terms of lip region shape, tail shape, and stylet length. However, Neodolichodorus bachlongviensis sp. n. can be distinguished from each of these species based on specific morphological traits, including the position of the phasmid, separation of the labial region, body length, tail length, stylet length, cuticle annulation in the labial region, and the morphometric indices. Cluster and Multi-Dimensional Scaling (MDS) analyses also indicated that Neodolichodorus bachlongviensis sp. n. is insignificantly similar to other species of Neodolichodorus. Furthermore, molecular characterizations of Neodolichodorus bachlongviensis sp. n. based on the D2-D3 region of 28S rDNA and the COI mtDNA region have provided valuable insights into the genetic makeup and relationships of this newly discovered species. Remarkably, our study provides the first COI mtDNA sequences of the genus Neodolichodorus, facilitating future research on molecular aspect of this genus.