Australasian Plant Disease Notes最新文献

Severe infection of stem rot was observed on plants of Withania somnifera during January and February of 2020 and 2021. Initial symptoms appeared on the plants showing paleness at infected areas, cottony, fluffy white mycelia was observed on the leaves, stem and inflorescence. In advanced stage of infection wilting of stem and defoliation was observed leading to partial or whole plant death. Based on its morphological and molecular traits, the fungus was identified as Sclerotinia sclerotiorum. Pathogenicity test was performed under controlled conditions resulting in similar symptoms to those observed in field. To the best of our knowledge, this is the worldwide first evidence of S. sclerotiorum causing stem rot disease on W. somnifera.

The Malayan apple is a tropical fruit known by various names, such as red guava and Malay rose apple. Originating in Southeast Asia, it has shifted from being an ornamental tree to being cultivated in India to meet global demand. Well-known for its health benefits, the fruit is rich in vitamins, minerals, and antioxidants. In May 2023, Malayan apple trees in Karnataka, India, displayed anthracnose symptoms, with a 20–25% disease incidence. The fungus C. nymphaeae was isolated, identified, and confirmed through multigene phylogeny. Its pathogenicity was validated by artificially infecting Malayan fruits, causing anthracnose symptoms and fulfilling Koch’s postulates. This represents the initial documented occurrence of C. nymphaeae causing anthracnose in the Malayan apple in India and the world, emphasizing the significance of this research in disease management.

Downy mildew is a production limiting factor for Brazil’s main onion producing region. In the present study we tested two management strategies, namely the utilization of a resistant cultivar and the implementation of a disease alert system. Our objective was to mitigate the frequency of systemic fungicide applications while concurrently sustaining optimal yield levels. By carrying out fungicide sprays only when the alert system indicated a severe risk and using the cultivar “SCS379 Robusta”, it was possible to reduce the number of sprays from 11 (calendar) to 5 (alert system), maintaining statistically similar yields (32.58 tonnes/ha – calendar; and 30.76 tonnes/ha – alert system). The reduction in spray applications using an integrated management strategy reduced the cost of spraying by more than half from BRL 0.069/Kg to BRL 0.033/Kg. This study demonstrates that implementation of an integrated management strategy can reduce chemical use and cost without compromising the protection of onion using alert system and more susceptible varieties.

A new leaf blight disease in Schleichera oleosa seedlings was detected in a Kerala state forest nursery, India. Through morphological, cultural characterization, and multi-gene phylogenetic analysis, the fungal pathogen was identified as Pseudopestalotiopsis camelliae-sinensis, the first report on Schleichera in India. Koch’s postulates were fulfilled. Research attention is required to manage emerging seedling diseases for quality planting materials.

In Mexico, manzano pepper (Capsicum pubescens) is a crop of economic importance. In 2022, in the municipality of Taxco de Alarcon, Guerrero, Mexico, leaf spots were observed in the mazano pepper crop. The fungus Alternaria spp., was consistently isolated from symptomatic leaf of manzano pepper. A molecular characterization was carried out by amplification and sequencing of the internal transcribed spacer (ITS) region of ribosomal DNA, major allergen (Alt a 1), and anonymous gene region (OPA10-2). BLAST analysis indicated similarity that varied from 99.5 to 100% with Alternaria arborescens sequences in GenBank. A phylogenetic analysis was carried out using the Maximum Likelihood method of two isolates of Alternaria sp., obtained from manzano pepper, and indicated that they were clustered with A. arborescens sequences (CBS 115189 and CBS 112749). Using uninjured two month-old plants grown in greenhouse conditions, Koch’s postulates were verified and fulfilled. To our knowledge, this is the first report of Alternaria arborescens as a caused leaf spot in manzano pepper in Mexico and in the world.

Basil (Ocimum basilicum) is an important aromatic and medicinal plant and is extensively cultivated for essential oil production. During the growing season of 2021–22, Sclerotinia stem rot has consistently been observed on basil at the Dr. Rajendra Prasad Central Agricultural University, Pusa, Bihar, India. Cottony, white mycelium and large, black sclerotia were observed on brown lesions on the stems and leaves of infected plants. The causal organism was identified as Sclerotinia sclerotiorum based on its morphological and molecular characterization.

The parasitic guava root-knot nematode, Meloidogyne enterolobii Yang and Eisenback (syn. M. mayaguensis), has a wide distribution, host range and is established majorly in tropical-subtropical climates. A routine diagnostic analysis of symptomatic plant roots confirmed the first detection of M. enterolobii in Australia, near Darwin, Northern Territory. The morphology of female perineal patterns, second stage juveniles (J2s) and males were consistent with other reports of this species. The presence of M. enterolobii was first evaluated with a species-specific sequence-characterized amplified region (SCAR) and the intergenic spacer region (IGS2), followed by sequencing of the mitochondrial cytochrome c oxidase I and II (COI & COII) and large subunit ribosomal RNA (28S rRNA) gene regions. The nematode was detected on several important crop-host plants in Australia’s Northern Territory including chilli, tomato, capsicum, cucumber, pumpkin, eggplant, snake bean and sweet potato. The ability of M. enterolobii to colonise a variety of weeds and native Australian plants makes management challenging. The route of introduction of M. enterolobii is presently unknown but is under investigation.

Crocus sativus L. leaf samples were serologically tested for the presence of beet western yellows virus (BWYV) and 17.6% of samples showed positive reaction. The partial genome sequence of the BWYV isolate-Saf-Th16 from saffron was closely related to that of BWYV isolates from citron in the USA. This is the first report of BWYV on saffron plants from Iran.

Previously unknown postharvest rots in Packham’s Triumph pear were detected in a batch of long-term cold-stored fruit during 2022 in North Patagonia, Argentina. Rots were characterized according to their symptoms and the causal agent was isolated and identified through cultural and molecular methods. Pathogenicity tests were performed on different pear cultivars both at 20 °C and under storage conditions (0 °C − 95% RH). Koch’s postulates were fulfilled by re-isolation of the pathogen. Our results indicated that Phacidiopycnis pyri was the causal agent of postharvest rot in the fruit examined. This would constitute the first report of P. pyri as a causal agent of postharvest decay in Argentina.

Sclerotinia stem rot on South African groundnut was previously attributed to Sclerotinia minor, but recent infections prompted a re-evaluation. Isolates underwent a species-specific PCR and phylogenetic analysis, confirming them as S. sclerotiorum. Koch’s postulates were fulfilled, demonstrating pathogenicity. Inoculation caused disease symptoms, with subsequent re-isolation matching the original strains. This study identifies S. sclerotiorum as the causative agent of Sclerotinia stem rot on groundnut in South Africa.