First Report of Shoot Blight of Grapevine Caused by Sclerotinia sclerotiorum in Illes Balears, Mallorca, Spain.

In 2021, grapevines (Vitis vinifera L.) cv. Callet growing in a commercial vineyard located at Pollença (northeast of the island of Majorca, Spain) showed severe symptoms of shoot blight during spring and early summer, with an incidence of 70%. Symptoms consisted of elongated cankered-like lesions, surrounded by water-soaked darker tissues, that developed at the base or around the middle nodes of the shoot. For fungal isolation, shoot samples with lesions were collected, surface disinfected with 2% NaCl for 90s, rinsed twice with deionized water and placed in Petri plates containing potato dextrose agar (PDA). The plates were incubated at 25°C under 12 h light-darkness for 6 days. Isolations consistently yielded on kind of fungal colonies that produced white mycelium and black spherical to elongated sclerotia (2 to 10 mm in diameter). Morphological characterization was consistent with the description of Sclerotinia sclerotiorum (Lib.) de Bary (Bolton et al. 2006). Three isolates (UIB 118-1, UIB 118-26, and UIB 129-41) were preserved and deposited in the Culture Collection of Microbiology-Faculty of Sciences, University of Balearic Islands, Spain. Genomic DNA was extracted from isolates UIB 118-26 and UIB 129-41 using the EZNA Miniprep Kit (Omega Bio-Tek, Norcross, GA). The internal transcribed spacer (ITS) region of ribosomal DNA, ß-tubulin (BTUB) and calmodulin (CAL) gene regions were amplified using ITS1F-ITS4 (Gardes and Bruns, 1996; White et al. 1990), Bt-2a/Bt-2b (Glass and Donaldson 1995) and CAL228F/CAL737R (Carbone and Kohn 1999) primer sets, respectively. Amplicons were sequenced and deposited in GenBank with accession numbers MZ604647 and MZ604648 for ITS, OK634402 and OK634403 for BTUB and OK634404 and OK634405 for CAL. BLASTn search showed that isolates were >99 % (ITS, BTUB and CAL) identical to S. sclerotiorum GenBank accession no. KF859933, CP017815 and KF871381, respectively. Pathogenicity tests were conducted using eight one-year old grapevines cv. Cabernet Sauvignon. Old and new green shoots were inoculated by inserting a 6-mm plug of mycelium taken from actively growing cultures on PDA into cuts made at the base and at the distal part of each shoot with a sterile scalpel with a total of eight inoculation points per plant. Inoculated wounds were sealed with Parafilm tape to avoid rapid dehydration. Inoculated plants and an equal number of wounded but non-inoculated plants (negative controls) were maintained at 25 ± 1°C for 48 h in plastic containers to ensure a high relative humidity (>90%). After 5 days, the infection girdled and rotted the green new shoots, whereas the older partially lignified shoots developed a localized long brown lesion that reached 16 cm in length. Due to the rotting of the basal part of the petiole, leaves turned gray, wilted, and died, easily detaching from the stem. In advanced stages of the disease, 7 days after infection, branches died and fell with the leaves remained attached (Fig 1 A, B). Reisolations from diseased shoots were successfully performed on PDA to fulfill Koch's postulates. S. slerotiorum was previously reported on grapevine causing shoot blight in Chile (Latorre and Guerrero, 2001), Korea (Jong-Han et al. 2009), California-USA (Boland and Hall, 1994) and Australia (Hall et al. 2002). AlsoS. sclerotiorum was reported among the endophytic mycobiota associated with Vitis vinifera in the Iberian Peninsula (Gonzalez and Tello, 2011) but not as a pathogen causing visible symptoms on that crop. So, this is the first report of the occurrence of S. slerotiorum as a pathogen of grapevines in Spain causing symptoms of canker and shoot blight. This finding highlights a potential risk of this fungal disease for the wine industry in the Mediterranean region and specially for Spain, the country with the largest acreage devoted to grapevines. Although chemical and biological are suitable control strategies, disease management is difficult as sclerotia of Sclerotinia can remain in the soil for up to eight years (Adams and Ayears, 1979), and preventive surveys are greatly recommended as an important epidemiological tool to monitor the epidemiology of disease and identify potential outbreaks of this new pathogen on grapevine in Spain.

In Vitro Antagonistic Activity of Trichoderma harzianum against Fusarium sudanense Causing Seedling Blight and Seed Rot on Wheat.

Fusarium sudanense is a novel fungus recently isolated from asymptomatic samples of wheat grains in Argentina. The fungus caused symptoms of seedling blight and seed rot on wheat after artificial inoculations. It is known that the production of mycotoxins by pathogens belonging to the Fusarium genus is harmful to human and animal health. Moreover, the warm and humid conditions that are favorable for growth and mycotoxin production of these species put the Argentinian wheat production area at a high risk of mycotoxin contamination with this novel pathogen. The aim of this work was to evaluate the antagonistic effect of Trichoderma harzianum against F. sudanense under in vitro tests at different environmental conditions. Fungi were screened in dual culture at different water activities (αw) (0.995, 0.98, 0.95, and 0.90) and temperatures (25 and 15 °C). The growth rate of the fungi, interaction types, and dominance index were evaluated. Also, the interaction between T. harzianum and F. sudanense was examined by light and cryo-scanning microscopy. T. harzianum suppressed the growth of F. sudanense at 0.995, 0.98, and 0.95 αw at 25 °C and 0.995 and 0.98 αw at 15 °C. Macroscopic study revealed different interaction types between F. sudanense and T. harzianum on dual culture. Dominance on contact where the colonies of T. harzianum overgrew the pathogen was the most common interaction type determined. The competitive capacity of T. harzianum was diminished by decreasing the temperature and αw. At 0.95 αw and 15 °C, both fungi grew slowly, and interaction type "A" was assigned. Microscopic analysis from the interaction zone of dual cultures revealed an attachment of T. harzianum to the F. sudanense hyphae, penetration with or without formation of appressorium-like structures, coiling, plasmolysis, and a veil formation. According to our results, T. harzianum demonstrated capability to antagonize F. sudanense and could be a promising biocontrol agent.

DNA phylogeny reveals polyphyly of Phoma section Peyronellaea and multiple taxonomic novelties.

Species of the anamorph genus Phoma are commonly isolated from a wide range of ecological niches. They are notoriously difficult to identify due to the paucity of morphological features and the plasticity of these when cultivated on agar media. Species linked to Phoma section Peyronellaea are typified by the production of dictyochlamydospores and thus have additional characters to use in taxon delineation. However, the taxonomy of this section is still not fully understood. Furthermore the production of such chlamydospores also is known in some other sections of Phoma. DNA sequences were generated from three loci, namely ITS, actin, and 3-tubulin, to clarify the phylogeny of Phoma taxa that produce dictyochlamydospores. Results were unable to support section Peyronellaea as a taxonomic entity. Dictyochlamydospore formation appears to be a feature that developed, or was lost, many times during the evolution of Phoma. Furthermore, based on the multigene analyses, five new Phoma species could be delineated while a further five required taxonomic revision to be consistent with the genetic variation observed.

First report of Phoma sorghina (Sacc.) Boerema Dorenbosch & van Kest on wheat leaves (Triticum aestivum L.) in Argentina.

A new disease caused by Phoma sorghina has been detected for the first time on wheat plants in the Province of Buenos Aires, Argentina. The pathogen was isolated from wheat leaves growing under field conditions, cultured on PDA and identified by its morphobiometric and cultural characters. The disease symptoms and morphological characters of the pathogen are described. Pathogenicity of the isolate was confirmed by inoculating 10 wheat cultivars under greenhouse conditions.