Australasian Plant Disease Notes最新文献

During September of 2020, Fruit suspected to be rot were observed on Choerospondias axillaris grown in an plantation in Yichun, Jiangxi, China. Approximately 10% of the fruit was discovered to be infected. The morphological features of the fungal isolate was identical to the features of Botryosphaeria dothidea. Phylogeny of concatenated sequences of the ITS, SSU, LSU and TUB2 genes were used to identify the causative agent as B.dothidea. Pathogenicity tests confirmed that this fungal species is the causal agent to C. axillaris. To the best of our knowledge, this is the first report of B. dothidea on C. axillaris in China and the world.

Medicinal plants have been used since the dawn of human civilization and over the years have gained attention in the academic community due to their use beyond folk medicine. Numerous plants make up recipes to suppress symptoms of various illnesses, with emphasis on plants of the genus Plectranthus and their antimicrobial properties. In July 2016, P. ornatus plants observed in a garden located in Recife, Pernambuco state, Brazil, which demonstrated symptoms of dry stem rot. Two fungi isolated from stem lesions were identified by morphological comparisons and combined DNA sequences as Lasiodiplodia theobromae. This is the first report of this pathogen in this medicinal plant in the world.

Brown circular stem canker symptom was observed on common bean plants in Mahallat county, Markazi province, Iran, in the summer of 2022. Five identical associated fungal isolates were recovered from the infected plants. Morphological and molecular characterization of the representative isolate (UTR38) using the partial sequence of beta-tubulin, and as well as RNA polymerase II second largest subunit loci was done. The associated fungus was identified as Paramyrothecium roridum. Pathogenicity of the isolate UTR38 was conducted on six-week-old seedling stems of the P. vulgaris cultivar Sunray. The inoculated fungus was also reisolated from the inoculated plants to fulfill the Koch’s postulates. According to the results, this is the first report of P. roridum as the causal agent of stem canker disease in P. vulgaris in Iran and worldwide.

During routine field surveys in February 2023, in a commercial field located in Hegazah village, Qus, Qena governorate, Egypt (25°50’49"N 32°49’33"E), powdery mildew symptoms were observed on leaves of a local cultivar of fenugreek (Trigonella foenum-graecum L.). Microscopic characterization showed that conidiophores were cylindrical, hyaline, straight, erect to bent, forming conidia singly, primary conidia were apically narrowed, lanceolate, obtuse to pointed measuring, secondary conidia were ellipsoid or cylindrical, measuring. Germ tubes were close to the base. BLASTn results showed 100% similarity with the submitted sequences of Leveillula taurica for ITS rDNA, the obtained phylogenetic tree through the maximum likelihood method confirmed the BLASTn results. Morphological and molecular approaches confirmed the identity of Leveillula taurica (Lév.) G. Arnaud. The obtained ITS rDNA sequence was deposited in NCBI GenBank (OR472546). Pathogenicity tests were conducted, and Koch’s postulates were fulfilled with the fungus. To our knowledge, this is the first report of powdery mildew caused by L. taurica (Lév.) G. Arnaud. on fenugreek in Egypt.

Capsicum (Capsicum annum var. grossum Sendt.) is a popular and widely cultivated vegetable crop. The leaves showing white to grey irregular spots were collected. The organism was isolated and cultured on potato dextrose agar from the diseased samples. The pathogenicity was proved on capsicum seedlings by inoculating hyphal suspension of the organism and koch’s postulates were proved by re-isolating the pathogen. The pathogen was identified as Stemphylium lycopersici based on morphological, cultural and molecular investigation (ITS, gapdh and cmdA). This is the first report of Stemphylium lycopersici causing leaf spot of capsicum in India.

Zinnia elegans of Family Asteraceae is a flowering plant grown widely in gardens in Indonesia. The plant is also often integrated into pest management of different agricultural commodities as its colourful flowers may attract beneficial insects including natural enemies. A total of eight viral symptomatic and four non-symptomatic Z. elegans samples were collected from four districts in Kulon Progo and Sleman Regencies of Special Region of Yogyakarta. They were molecularly tested using two universal primer pairs for begomoviruses, and two specific primer pairs for cucumber mosaic virus (CMV, Cucumovirus) detections. The eight symptomatic samples were all positive for CMV but negative for begomoviruses infections. The four non-symptomatic samples were tested negative to begomoviruses and CMV. Partial RNA2 and RNA3 segments of four CMV isolates were sequenced to demonstrate that they are members of subgroup IB. 4Ze-Ngaglik isolate was shown to be mechanically transmitted to healthy Z. elegans and cucumber cv. Baresta (Cucumis sativus). To the best of our knowledge, this report confirmed the first CMV occurrence in Z. elegans in Indonesia.

Bacterial soft rots are among the most economically important diseases that cause significant yield losses in various crops. During 2022 and 2023, widespread occurrence of soft rot disease was observed in sugar beet fields in the Firuzan region, Hamedan Province, Iran. From the sugar beet plants with soft rot symptoms, a bacterial isolate was obtained that was obligately aerobic, negative for Gram, oxidase, levan, and arginine dihydrolase tests, and positive for pectinase, urease and hypersensitivity reaction on tobacco. Koch’s postulates confirmed its pathogenicity by developing soft rot symptoms in sugar beet plants. The 16SrRNA and rpoD sequences from this isolate were most closely related to Pseudomonas punonensis LMT03 with 99.8% and 94.7% identity, respectively and then to Pseudomonas argentinensis LMG22563 (= CH01) with 99.4% and 94.3% identity values. To our knowledge, this is the first report of a Pseudomonas sp. strain causing soft rot disease in sugar beet worldwide.

Orchids are among the most cultivated flowers in the world. Plants of Dendrobium thyrsiflorum (DT) and Cattleya wittigiana (CW), cultivated at the Botanic Garden of Bauru in São Paulo, Brazil, presented black rot symptoms. The causal organism was identified as P. palmivora on DT and P. nicotianae on CW orchids based on its morphological and molecular characterization. Inoculation caused disease symptoms and Koch’s postulates were fulfilled by re-isolation of the pathogen.

Papaya trees showing disease symptoms caused by root-knot nematodes (Meloidogyne spp.) were detected in a tropical fruit farm in Vero Beach, FL, USA. Roots were severely galled containing a high population density of root-knot nematode eggs. The nematode species causing damage was identified as M. incognita based on the morphometrics of body, stylet, and tail length of the second-stage juveniles, and morphological characteristics of female perineal patterns. Molecular analyses using both species-specific and universal primers also confirmed the species identity. A pathogenicity test confirmed M. incognita reproduction on papaya by producing nematode females and egg masses within the root galls. This report documents the first confirmed detection of M. incognita in papaya in Florida, USA, providing detailed information on the nematode's morphology characteristics and DNA sequence data.

Sri Lankan cassava mosaic virus (SLCMV) is one of the viruses that cause cassava mosaic disease. Strong mosaic symptoms on a cassava plant in the Northern Territory tested positive in begomovirus specific PCR testing. The DNA sequence of the amplicon was 96.38% similar (over 528 bp) to SLCMV, a result confirmed by sequencing genomic DNA. This is the first record of SLCMV in Australia, and outside of Asia.