Australasian Plant Pathology最新文献

Yam (Dioscorea spp.) is used not only as food in the world but also as an important traditional medicinal herb in East Asia. However, its yield and quality are severely affected by leaf spot disease. Isolating and identifying the novel pathogens will be very helpful for controlling yam leaf spot disease. In 2023, leaf spot disease occurred in about 40% yam from germplasm resource nursery in Wen County (N34°94′68′′, E112°98′22′′), Jiaozuo City, Henan province, China. In the present study, morphological and molecular analysis methods were used to screen for novel pathogens from diseased leaves. Based on morphological characteristics, the isolates from diseased yam leaves mainly belonged into reported pathogenic fungi genera causing leaf spot. Notably, the HSD-JZ8 displayed Schizophyllum-like morphology features. The phylogenetic analysis of phylogenetic analyses of multi-loci (internal transcribed spacers (ITS) and nuclear ribosomal small subunit (SSU)) confirmed HSD-JZ8 as Schizophyllum commune. The pathogenicity of S. commune is confirmed by Koch’s postulates. To our knowledge, this is first report of wood-rot fungus S. commune as the pathogen causing leaf spot on yam worldwide, suggesting that herbs might be new hosts for S. commune in the world.

Black root rot of cotton is a serious production constraint for the cotton industry in Australia. It is caused by the ascomycete Berkeleyomyces rouxiae which is a broad host range pathogen. To date there has been minimal genomic surveying in this genus and herein we report two high quality genome assemblies for cotton-derived isolates.

The genus Hirschmanniella comprises economically important plant-parasitic nematodes associated with aquatic and semi-aquatic plants, especially rice. In this study, the occurrence and distribution of Hirschmanniella spp. across six northern provinces of Vietnam were studied. Three species: H. mucronata, H. oryzae, and one unidentified Hirschmanniella sp were recorded. Among them, H. mucronata was the most prevalent, detected in five provinces with a high frequency of occurrence (up to 83.3%) and considerable population densities (up to 159 ± 192 individuals/250 g soil), especially in Vinh Phuc. H. oryzae was mainly detected in Hai Phong, with moderate density and limited distribution. The unidentified Hirschmanniella sp. was restricted to Nam Dinh with low frequency and density. These findings highlight the dominance of H. mucronata in northern Vietnam’s rice ecosystems and suggest potential taxonomic diversity requiring further investigation. Additionally, an updated checklist of valid Hirschmanniella species was provided. To facilitate species identification, a user-friendly browser-based interactive key that integrates morphological characters for distinguishing Hirschmanniella species was also designed. This study provides essential baseline knowledge on rice-associated nematodes, supporting diagnostics, taxonomy, and future research aimed at sustainable management of nematode pests in rice production in Vietnam and beyond.

Chrysanthemum stunt viroid (CSVd) is reported for the first time in trailing verbena in nursery stock in New Zealand. RT-PCR with published Pospiviroid primers detected CSVd in four of seven vegetatively propagated samples from a commercial nursery but not in seed propagated plants from a national retail chain. The isolate had 99% identity with isolates from overseas. Plants were also infected with a number of viruses which may be masking CSVd’s effect on its host. This finding highlights verbena as a previously unrecognised potential reservoir of CSVd in the country’s nursery and horticulture industries.

A new leaf spot disease in Bauhinia purpurea tree was detected in Kerala Agricultural University Campus, Thrissur, Kerala state, India. The foliar pathogen was isolated on Potato Dextrose Agar (PDA) medium after surface sterilizing the leaf bits with 0.1% mercuric chloride. The inoculated plates were incubated at room temperature (25 °C). Koch’s postulates were fulfilled, and the pathogen was identified as Colletotrichum siamense based on morphological and cultural characteristics, along with multi-gene phylogenetic analysis. Ecological and pathological significance of emerging fungal pathogens within tree-pathogen systems deserve research focus.

Bacterial wilt disease in plants, historically attributed primarily to the strains of Ralstonia solanacearum species complex, is undergoing re-evaluation due to recent discoveries. While the strains of R. solanacearum species complex remain major pathogens, emerging evidence reveals a broader spectrum of bacterial pathogens from the Enterobacteriaceae family, including Enterobacter cloacae, Enterobacter mori, Klebsiella oxytoca, Kosakonia cowanii and Serratia marcescens, as well as Providencia vermicola from the Morganellaceae family, all implicated in causing comparable wilt symptoms in plant hosts traditionally associated with R. solanacearum species complex. Although much remains to be understood about their pathogenicity and infection mechanisms, recent advancements through whole-genome sequencing have provided limited but valuable insights into their potential virulence factors.

Phytochemicals from natural sources are increasingly recognized as promising substitutes for synthetic fungicides. The current study assessed the effectiveness of lemongrass extract (LGE) in managing stem-end rot diseases in mango fruit caused by the fungus Lasiodiplodia theobromae. The minimum inhibitory concentration (MIC) for LGE was determined to be 2.00 g/L, indicating its potential use as a preventative, as well as for simultaneous and curative measure for stem-end rot diseases in mango fruit. Moreover, results revealed that LGE at 2.0 g/L concentration outperformed synthetic fungicides (mancozeb 2.5 g/L) in both toxicity and effective volume concentration against L. theobromae. These findings underscore the potential of LGE as a possible substitute to conventional chemical fungicides in agricultural practices.

Twenty-nine chemical compounds were identified in LGE. The four major compounds were as follows: 2-monopalmitin (19.64%), α-citral (16.44%), α-monostearin (13.95%), and β -citral (12.00%).

Red rot compromises sugarcane production, causing severe yield losses. Symptomatic leaf samples were collected from a commercial plantation in Alagoas, Brazil. The isolated pathogen was identified by morphological, cultural, pathogenicity, and phylogeny studies, confirming the occurrence of F. tanahbumbuense causing red rot in sugarcane worldwide.

The diagnosis of viral diseases in cowpea is crucial for the efficient implementation of control measures. A multiplex reverse-transcription polymerase chain reaction (RT-PCR) assay was developed for the simultaneous detection of cowpea severe mosaic virus (CPSMV), cucumber mosaic virus (CMV), and cowpea mild mottle virus (CPMMV) in cowpea. The targeted viruses produced the expected amplicons, namely 300 bp for CMV, 500 bp for CPMMV, and 890 bp for CPSMV. The relative analytical sensitivities of the assay was determined through probit analysis of serial dilutions (10⁻¹ to 10⁻⁶), with detection limits at 95% probability established as 10^− 2 for all viruses in multiplex RT-PCR. The performance of multiplex RT-PCR was confirmed by uniplex RT-PCR for each target virus. The multiplex RT-PCR of field cowpea leaf samples revealed a high incidence of CMV and CPSMV, and no infection by CPMMV. Approximately 24% of the samples were simultaneously infected with CPSMV and CMV. No other comovirus, besides CPSMV, was detected, when the samples were tested with degenerate primers for comoviruses by uniplex RT-PCR. This assay streamlines the diagnosis of CPSMV, CMV, and CPMMV by offering a cost-effective and efficient tool. Additionally, it supports epidemiological studies of these pathogens, providing critical data to inform effective control strategies.

Rust symptoms were observed in the matured leaves of Xanthium strumarium L. plants near paddy fields in the Chengalpattu district of Tamil Nadu, India. The teliospores were observed under microscope and their morphological characters were studied. To further confirm the identity of the pathogen, the spores were collected in sterile distilled water and DNA was extracted using CTAB method. The phylogeny analysis revealed that the pathogen observed was Puccinia xanthii Schw. The pathogen was closely related to other isolates of Puccina xanthii Schw. reported from X. oriantale from Okcheon-gun, Korea. This is the first report of Puccinia xanthii Schw. in Xanthium strumarium L. reported in India.