Australasian Plant Disease Notes最新文献

Vetiver is currently cultivated in Indonesia; however, it is susceptible to leaf spot disease. Although usually minor, this hampers growth under favourable conditions. Through morphology and genetics study, we identified Curvularia akaiiensis as the causative agent, marking the first documentation of its role in vetiver leaf spot disease.

A study of postharvest diseases in mangoes in Tanauan, Batangas, situated in Southern Luzon, Philippines, led to the isolation of a fungal pathogen causing stem-end rot and fruit rot disease in the Philippines. The disease is characterized by water-soaked brown lesions associated with white mycelial growth in the late stage of infection. The causal agent was identified as Neofusicoccum mangiferae using morphology and DNA sequencing of the translation elongation 1 (TEF1) and internal transcribed spacer (ITS) gene regions. This is the first report of Neofusicoccum mangiferae from the Philippines.

Five grapevine viruses, including grapevine geminivirus A (GGVA), grapevine Syrah virus 1 (GSyV-1), grapevine Cabernet Sauvignon reovirus (GCSV), grapevine virus F (GVF) and grapevine Red Globe virus (GRGV) have been detected in four South Australian vineyards using metagenomic high throughput sequencing for the first time in Australia. Most of them were present in asymptomatic grapevines and some were present in grapevines with leafroll disease that were infected by several other viruses, including grapevine leafroll-associated viruses. Therefore, the association of GGVA, GSyV-1, GCSV, GVF and GRGV with disease in Australia is unknown.

The genus Pratylenchus is the most economically important nematode for yam. Samples of tubers and soil of Dioscorea cayenensis and D. alata were collected in states of Brazil. Through morphometric characterization and molecular analysis of the ITS and 28S rDNA regions, the nematode Pratylenchus zeae was identified. This is the first report of P. zeae in yam in Brazil.

Plants of Cereus jamacaru with root necrosis symptoms were observed in Acopiara City, in the state of Ceará, Brazil. Using morphological characterization and molecular analysis of the ITS and 28 S rDNA regions, Pratylenchus zeae was identified as the etiological agent, confirmed by infection and re-isolation of the nematodes. This is the first report of P. zeae causing root necrosis symptoms in C. jamacaru.

Ambarella (Spondias dulcis) tropical fruit showing typical galling symptoms caused by root-knot nematode was discovered in the orchard located in Phaya Yen, Pak Chong district Nakhon Ratchasima province, Thailand. The nematode was identified based on morphological and molecular information and its pathogenicity was confirmed through inoculation of second-stage juveniles into ambarella seedlings under greenhouse conditions. This was the first report of Meloidogyne javanica infecting S. dulcis.

Apple stem grooving virus, the causal agent of citrus tatterleaf disease, was detected for the first time in the Lao People’s Democratic Republic. Samples were collected from citrus trees across the southern provinces for testing in Australia. RNA was extracted and tested using conventional and real-time reverse transcription polymerase chain reactions with the virus detected in 1 of 59 samples tested. Viral identity was confirmed by Sanger sequencing and high throughput sequencing.

Turkey is among the top 10 producers of cucumber, melon, watermelon, and squash in the world. Lately, seed-borne viruses have become a major issue in greenhouse and field-grown cucurbits. In this study, the incidence of kyuri green mottle mosaic virus (KGMMV) was determined in seeds from various species (cucumber, melon, watermelon, summer squash, bottle gourd, winter squash) of Cucurbitaceae. KGMMV detection in a total of 20 seed lots of each cucurbit species was done by enzyme-linked immunosorbent assay (ELISA) and RT-PCR. The highest virus incidence was 45% in melon followed by 25% in cucumber and 10% in squash. To the best of our knowledge, this is the first report of KGMMV in cucurbit crops in Turkey and this highlights the potential risk of KGMMV to commercial cucurbit seed lots.

During a survey of the mycobiota of sourgrass (Digitaria insularis), a graminaceous weed from Brazil, severe foliage blight symptoms were observed on plants at different places of the state of Minas Gerais. A fungus identified as Bipolaris yamadae, after a polyphasic study, including analysis of ITS, GPDH and TEF-1α genes, was isolated from diseased tissues. Pathogenicity to sourgrass was confirmed through inoculations of healthy plants. This is the first report of B. yamadae causing foliage blight on D. insularis in Brazil and worldwide.