Australasian Plant Pathology最新文献

Coffee leaf rust (CLR) poses a significant threat to coffee crops worldwide, including those grown in Brazil. CLR thrives in climatic conditions ideal for coffee cultivation, which results in its constant presence in Brazilian coffee farms. The intensity of CLR exhibits variations as affected by interannual and spatial climate variability that shape epidemics. The aim of this study was to determine the agro-climatic favourability zones for CLR occurrence in the major coffee-producing regions of Brazil based on region-specific agro-climatic conditions. Climate data spanning from 1961 to 2015 at 46 sites were selected to represent the major coffee-producing regions. Using a CLR infection rate model, daily simulations were performed to calculate the cumulative infection rate (CIR) for each site and growing season, starting from 1^st October to 30^th June of the following year. Based on the CIR values, the sites and seasons were categorised into five favourability classes: Very Low, Low, Medium, High, and Very High. An Agro-Climatic Favourability index (ACFav_index) was developed, considering the frequency of seasons falling within each favourability class. A map displaying four distinct favourability zones across the studied regions was then obtained and showed that most of the traditional coffee-growing areas fell within the Medium to High Favourability zones for CLR. The obtained map, delineating CLR favourability zones, holds practical value for coffee growers, consultants, and policymakers alike. It can guide the selection of CLR-resistant coffee cultivars for new cultivation areas and aid in the development of effective disease control strategies.

Arecanut is an important commercial plantation crop in India, and many farm families depend solely on the arecanut industry. In July 2018, immature nuts were shed heavily due to fruit rot disease in the Western-Ghats region. Though the symptoms were suggestive of common fruit rot disease, they appeared to be unusual. The associated pathogen was isolated from the infected tissue using the standard isolation technique, and an oomycete fungus was consistently isolated from infected nuts. Based on the colony and spore morphology, the pathogen was identified as Phytophthora sp. and by multi-gene sequencing (ITS, β-tub, TEF-1α, and Cox-II) confirmed it as Phytophthora parsiana. The pathogenicity of the isolate (P25) was established by inoculating healthy arecanut fruits with the pin-prick method. To our knowledge, this is the pioneering work that represents the first report of Phytophthora parsiana infecting arecanut in Western-Ghats of Southern India.

The pulse crops widely cultivated in South India for their protein rich grains are negatively affected by whitefly-transmitted begomoviruses (genus Begomovirus, family Geminiviridae) causing yellow mosaic disease (YMD). Here, YMD-inducing begomoviruses were characterized from cultivation areas in Tamil Nadu, South India, with complete sequences of seven DNA-A and eight DNA-B components determined. The pairwise nucleotide sequence comparisons for complete DNA-A showed that both mungbean yellow mosaic virus (MYMV) and mungbean yellow mosaic India virus (MYMIV) were present. The comparisons of nucleotide sequences of YMD begomoviral isolates revealed the presence of five groups of DNA-B components, which showed only 81–88% identity in the common region with their cognate DNA-A. The recombination analysis revealed significant events in the the non-coding and coding regions in DNA-B components, which were predicted amongst the MYMV isolates and between MYMV and MYMIV sequences. The partial tandem repeat constructs of MYMV and MYMIV DNA-A and DNA-B isolates (GenBank Accession Nos. KC911721, KC911724, AF142440 and AF126406) were infectious in blackgram (Vigna mungo), which showed typical YMD symptoms. Also the blackgram genotypes showed different levels of susceptibility and tolerance under experimental inoculation with MYMV and MYMIV. From the results, it is inferred that MYMV and MYMIV have occurred in mixed infection in blackgram.

In 2016 and 2017, circular and irregular leaf spots on globe artichoke (Cynara scolymus) were observed in seven locations of the Mediterranean region of Türkiye. In a preliminary microscopic examination, fungal spores in the leaf spots were similar to the genus Cladosporium. However, three different methods (direct transferring, agar-plate, and blotter) were used for isolation of possible causal agent(s) of those leaf spots. Based on morphological and molecular data (ITS and Actin), fungal colonies isolated from those leaf spots belonged to Cladosporium cladosporioides and Cladosporium pseudocladosporioides. Pathogenicity tests were fulfilled using globe artichoke seedlings of cv. Bayrampaşa in a greenhouse. In addition, to detect prevalence of the leaf spots on globe artichoke, surveys were conducted in 79 commercial fields in two consecutive years. As a result, mean disease incidence was 17.4% in 2016, while it was 24.4% in 2017. The results of the present study suggest that Cladosporium cladosporioides and Cladosporium pseudocladosporioides are associated with the leaf spots on globe artichoke. Cladosporium was previously reported to be associated with leaf spots on sycamore fig, papaya, pecan, wheat, eggplant, tomato and ladies palm. To the best of our knowledge, this is the first record of Cladosporium species causing leaf spots on globe artichoke in the world.