Australasian Plant Disease Notes最新文献

Fenugreek plants showing typical leaf curl disease symptoms were collected from Aurangabad, Maharashtra State, India. Begomovirus association with the five diseased in fenugreek was confirmed through PCR using begomovirus specific primers which resulted in expected amplicon of 1.2 kb product of virus genome. Analysis of the partial genome sequences obtained revealed that they have more than 95% nucleotide identity among themselves and showing similarity with begomoviruses reported earlier. Further, complete viral genome segments (DNA-A and DNA-B molecule) were amplified by RCA and DNA satellites by PCR were cloned and sequenced for one representative sample (F-TK). No PCR amplification resulted for alphasatellite specific primers in the infected fenugreek samples. Sequence analysis showed the nucleotide (nt) identity of 91.6—96.3 per cent for DNA-A and 90.2 to 91.9 per cent for DNA-B with several isolates of tomato leaf curl Kerala virus (ToLCKeV) and tomato leaf curl New Delhi virus (ToLCNDV) infecting tomato, respectively. Betasatellite showed maximum nt identity of 80.9 per cent with ToLCB infecting papaya will be considered as novel betasatellite as per ICTV classification criteria (less than 91% nt identity for complete DNAβ), for which we proposed the name, fenugreek leaf curl betasatellite. Recombination analysis of sequences of DNA-A, DNA-B and betasatellite of begomovirus associated with the fenugreek using RDP4 software indicated that they have are originated through recombination of begomoviruses infecting other crops. To the best of our knowledge this is the first report DNA-A of ToLCKeV, DNA-B of ToLCNDV and novel betasatellite associated with severe leaf curl disease of fenugreek from India.

In this report, we present the first description of nine complete genome sequences of a new strain of chayote yellow mosaic virus (ChaYMV, genus Begomovirus, family Geminiviridae), provisionally named Côte d’Ivoire (ChaYMV-CI), isolated from bitter melon (Momordica charantia) leaf samples showing yellow mosaic symptoms collected in the region of Abidjan in Côte d’Ivoire in 2013 and 2019. The nucleotide sequences of ChaYMV-CI DNA-A-like genome share the highest nucleotide sequence identities (91.8–92.5%) with those of ChaYMV isolates from Benin and Cameroon. Phylogenetic analysis confirmed the segregation of ChaYMV isolates into two distinct clades and their affiliation to Old World monopartite begomoviruses. The discovery of a new strain of ChaYMV in West Africa, at the limit of the taxonomic demarcation threshold for begomoviruses (91%), call for further investigations into the molecular diversity, geographical distribution and host range of ChaYMV in Western Africa.

In 2018, sclerotium rot was observed in sword beans (Canavalia gladiata DC.) grown in a field at Gyeongsangnam-do Agricultural Research and Extension Services. The disease mainly affected the stems and pods of sword beans that touched the ground. The stems that touched the ground were water-soaked at the start of the infection and rotted, slowly withered, and eventually died. White mycelia spread across the lesions, and numerous sclerotia formed on the petiole near the soil line. The sclerotia were globoid, 1–3 mm in diameter, and white to brown in color. Hyphae on PDA were 4–8 μm wide, and clamp connections were observed. Pathogenicity of isolated fungus on sword beans was confirmed according to Koch’s postulates. For molecular identification, we sequenced the entire ITS rDNA sequence of the causative fungus and analyzed its phylogenetic relationships. The fungi isolated from sword beans were in a clade r-1 containing the reference strains of A. rolfsii and S. delphinii. The 540-bp PCR amplicons corresponding to A. rolfsii-specific amplification were produced in all three isolates. Mycological characteristics, ITS rDNA sequencing, the species-specific PCR analysis, and pathogenicity in the host plant identified this fungus as Athelia rolfsii (Curzi) C.C. Tu & Kimbr. This is the first report of sclerotium rot on sword bean caused by A. rolfsii.

Gynostemma pentaphyllum, also known as Jiao-Gu-Lan, is a perennial liana belonging to the family Cucurbitaceae. This plant has been used as a traditional folk medicine for the treatment of various human diseases. In May 2020, G. pentaphyllum cultivated at the Research Station of Medicinal Plants at Tam Dao, Vinh Phuc, Vietnam was affected severely by root rot disease, resulting in leaf yellowing, wilting, and death. Based on morphology and sequence analysis of the ITS region, the pathogen was identified as Globisporangium attrantheridium. Koch’s postulates were fulfilled. This is the first report of Gl. attrantheridium as a pathogen causing root rot on G. pentaphyllum. This finding will be of importance for effective disease management.

This is the first report of grapevine polerovirus 1 (GPoV-1) on grapevine in South Africa. It was detected in ‘Katta Khurgan’ and ‘Kandari’ cultivars, using an RNAtag-seq with Illumina HiSeq sequencing and RT-PCR. GPoV-1 was a component of mixed infections with other viruses, therefore further work will be required to establish associated symptomatology.

In March 2016, grey mould disease was observed on mango (Mangifera indica) in Okinawa Prefecture, Japan. During the flowering period, the disease caused a brown coloration of the petals and peduncles accompanied by white aerial mycelium. As the disease symptoms progressed, the rot of panicle parts was accompanied by grey mould, resulting in fruit set failure. A fungus was isolated from the discoloured inflorescence into pure culture. Based on morphology and analyses of glyceraldehyde-3-phosphate dehydrogenase (g3pdh), heat-shock protein 60 (hsp60) and DNA-dependent RNA polymerase subunit II (rpb2) DNA sequences the fungus was identified as Botrytis cinerea. In an inoculation test, the isolate reproduced the symptoms observed on mango petals and peduncles and was reisolated from the flowers. This is the first report of B. cinerea as the causal agent of grey mould (haiirokabi-byo in Japanese) on floral tissue of mango in Japan.

Pennyroyal (Mentha pulegium) leaves with small irregular or ellipsoidal necrotic spots were collected in a suburb area of Ardal city, Chaharmahal and Bakhtiari province of Iran in summer 2018. A fungal isolate was recovered from diseased tissue and identified as Bipolaris sorokiniana based on morphological characteristics and a partial sequence of the gpdh gene. In a pathogenicity study, disease symptoms were observed on inoculated leaves after 14 days. The same pathogen was re-isolated and identified from diseased leaves, thus fulfilling Koch's postulates. This is the first report of B. sorokiniana causing leaf spots on Mentha pulegium in Iran and the world.