Australasian Plant Pathology最新文献

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.

The isolation of Phytopathogens from durum wheat grains obtained from twenty-eight locations in northeastern Algeria revealed the presence of two Cladosporium isolates in Algerian durum wheat seeds. A macro- and microscopic study was performed to identify these isolates, and the obtained result was confirmed by Molecular identification. Two tests were conducted on three durum wheat varieties to evaluate their pathogenicity on coleoptile and root length, as well as the basal parts. The results revealed that Cladosporium isolates caused a significant decrease in the coleoptile and root length, reaching 100%, and a diminution in the root and shoot length by 29.61% and 49.78%, respectively. It also caused a diminution in root and shoot fresh weight by 88.76% and 56.87%, respectively. Based on all these results, it is the first report of highly pathogenic isolates of Cladosporium colombiae on durum wheat plant in Algeria.

Anthracnose is one of the causes of significant reductions in chili yield and marketability worldwide. In Vietnam, anthracnose is also one of the most dangerous diseases of chili. This work aimed to identify Colletotrichum species causing chili anthracnose in Hue based on phylogenetic analysis of multiple locus genes such as ITS, act, cal, chs-1, gapdh, and tub2. The study determined 3 species of Colletotrichum, which were C. scovillei, C. truncatum, and C. siamense. Furthermore, the morphological features of these species were determined. The pathogenicity assays revealed that these species displayed different levels of virulence on artificially infected fruits such as chili, banana, mango, and dragon fruit. The incidence and lesion size of anthracnose disease in wounded fruits were higher than in unwounded fruits. Notably, the pathogenicity of C. truncatum on banana has not been previously reported and it. warns the banana industry that anthracnose caused by this species may appear on this fruit crop. Our study provides preliminary insights into the Colletotrichum species associated with chili anthracnose, which will assist in developing biocontrol strategies and managing post-harvest diseases that impact chili production in Vietnam.

Sclerospora graminicola, a destructive oomycete pathogen, is the causal agent of downy mildew in foxtail millet (Setaria italica L.), a devastating disease that severely impacts crop productivity. Antofine, an alkaloid isolated from Cynanchum komarovii Al. Iljinski, exhibits significant inhibitory effects on S. graminicola. This study evaluated the effects of 2% antofine suspension (applied via seed coating) on physiological traits, nutritional quality, and yield in foxtail millet. The results revealed that 2% antofine treatment significantly enhanced plant growth parameters, including plant height, total root length, and root-shoot ratio during both seedling and jointing stages. The enzymatic analysis revealed that 2% antofine treatment induced peak activity of key defense-related enzymes at the elongation stage, with catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), and phenylalanine ammonia-lyase (PAL) showing significant increases of 11.06%, 34.70%, 345.67%, and 8.68%, respectively, compared to the control. Field trials demonstrated a 66.81% disease control efficacy, accompanied by a 22.01% yield increase (4245.58 kg/ha). Notably, antofine application significantly improved grain quality, elevating total sugar (8.26%), soluble sugar (67.32%), yellow pigment (12.04%), vitamin C (46.29%) and crude protein (30.64%) contents. These results collectively indicate that antofine functions as a multifunctional agent that not only suppresses S. graminicola infection but also activates plant defense mechanisms, enhances stress tolerance, and improves crop productivity and nutritional value. The study provides compelling evidence for antofine's dual role as both an effective biocontrol agent and a plant growth regulator in foxtail millet cultivation systems.

Northeast India, particularly Assam, is a significant region for sericulture, home to the renowned Muga silkworms (Antheraea assamensis Helfer) that produce golden-hued silk. The primary feeding plants for these silkworms are Som (Persea bombycine King ex Hook. Fil. Kosterm) and Soalu (Litsea monopetala Juss). However, these plants are susceptible to diseases, including grey leaf spot, which affect leaf quality and silkworm productivity. This study aimed to identify the pathogen causing grey leaf spot on Som plants. Diseased leaf samples were collected from various locations in Assam, and fungal isolates were designated and analyzed using PCR with ITS-1 and ITS − 4 primers. The isolate BP2, identified through sequence analysis and BLAST^®, showed the highest homology (92.6%) with Neopestalotiopsis spp. strain NTUCC (accession number MT322112). The results were submitted, and the accession number OQ195903 was assigned by NCBI. Pathogenicity tests also confirm the pathogenic effect of the test isolate BP2. This study provides crucial insights into the pathogen responsible for grey leaf spot, aiding in developing management strategies for sericulture sustainability.

Most Australian vegetable growers apply fumigants or nematicides as a precautionary nematode control measure when crops susceptible to root-knot nematode (RKN, Meloidogyne spp.) are grown in soils and environmental conditions suitable for the nematode. The only way growers can make rational decisions on whether these expensive and environmentally disruptive chemicals are required is to regularly monitor RKN populations and decide whether numbers prior to planting are high enough to cause economic damage. However, such monitoring programs are difficult to implement because nematode quantification methods vary in efficiency and the damage threshold for RKN on highly susceptible vegetable crops is often < 10 root-knot nematodes /200 mL soil. Consequently, five nematode quantification methods were tested to see whether they could reliably detect these very low population densities of RKN. Two novel methods produced consistent results: 1) extracting nematodes from 2 L soil samples using Whitehead trays, quantifying the RKN DNA in the nematode suspension using molecular methods, and generating a standard curve so that the molecular results provided an estimate of the total number of RKN individuals in the sample, and 2) a bioassay in which two tomato seedlings were planted in pots containing 2 L soil and the number of galls produced on roots were counted after 21–25 days. Both methods could be used to quantify low populations of RKN, but bioassays are more practical because expensive equipment and facilities are not required and they can be done at a local level by people lacking nematological or molecular skills.

Fusarium wilt of cotton is a major production constraint worldwide caused by Fusarium oxysporum f. sp. vasinfectum. Strain variations contribute to differences in disease expression across different geographic locations. Genomes for two Australian isolates of F. oxysporum isolated from cotton are presented. The strains differ in their symptomatology on cotton plants and group in distinct lineages, different to those cotton infecting strains found overseas.

Tobacco (Nicotiana tabacum L.) is an economically important crop, widely cultivated in China. Since 2021, a new leaf spot disease has been seen frequently in Enshi, Xiangyang, Yichang, and Shiyan, all in Hubei Province, China. Diseased leaves exhibiting roundish lesions with greenish-yellow edges were collected to determine the causal agent in summer 2022. After isolation, morphological characterization, and molecular identification (ITS, LSU, and TUB), the pathogen of the new tobacco leaf spot disease was identified as Boeremia exigua. Inoculation tests showed that B. exigua strains could cause this disease on detached tobacco leaves, and fungi were re-isolated with morphology identical to the inoculated strain, confirming Koch’s postulates. This is the first report of tobacco leaf spot caused by B. exigua worldwide.

Rice (Oryza sativa L.) is a widely cultivated grain crop and a significant source of dietary carbohydrates. In 2019 and 2022, leaf blight disease was observed on rice in Jingzhou City, Hubei Province, China, that causal fungus was isolated from the disease lesions. Based on the morphological characteristics, sequences of internal transcribed spacer (ITS) of rDNA region and pathogenicity tests, it is identified as Alternaria padwickii (Ganguly) Ellis (1971), which is morphologically considered as Trichoconiella padwickii (Ganguly) Jain (1975). However, its molecular phylogeny is rare to know. According to the phylogenetic analysis of ITS, large-subunit ribosomal RNA (LSU) and RNA polymerase second largest subunit (RPB2) gene regions, the species should not belong to the genus Alternaria, which is the genus Trichoconiella in Pleosporaceae. This is the first report of leaf blight on rice caused by Trichoconiella padwickii in China and the determination of the phylogenetic position for Trichoconiella in Pleosporaceae.