Fungal Pathogens Associated With Canker Diseases of Almond in California

Abstract

Almond canker diseases are destructive and can reduce the yield as well as the lifespan of almond orchards. These diseases may affect the trunk and branches of both young and mature trees, and in severe cases can result in tree death soon after orchard establishment. Between 2015 and 2018, 70 almond orchards were visited throughout the Central Valley of California upon requests from farm advisors for canker disease diagnosis. Two major canker diseases were identified including Botryosphaeriaceae cankers and Ceratocystis canker. In addition, five, less prevalent canker diseases were identified including, Cytospora-, Eutypa-, Diaporthe-, Collophorina and Pallidophorina canker. Seventy-four fungal isolates were selected for multi-locus phylogenetic analyses of ITS1-5.8S-ITS2 (ITS), and part of the translation elongation factor 1-α (TEF1- α), β-tubulin (TUB2), and glyceraldehyde 3-phosphate dehydrogenase (GPD) gene sequences, which identified 27 species including 12 Botryosphaeriaceae species, Ceratocystis destructans, five Cytospora species, Collophorina hispanica, four Diaporthe species, two Diatrype species, Eutypa lata, and Pallidophorina paarla. The most frequently isolated species were C. destructans, Neoscytalidium dimidiatum and C. californica. Pathogenicity experiments on almond cv. Nonpareil revealed that N. parvum, N. arbuti and N. mediterraneum were the most virulent. Botryosphaeriaceae cankers were predominantly found in young orchards and symptoms were most prevalent on the trunks of trees. Ceratocystis canker was most commonly found in mature orchards and associated with symptoms found on trunks or large scaffold branches. This study provides a thorough examination of the diversity and pathogenicity of fungal pathogens associated with branch and trunk cankers of almond in California.

Identification and Characterization of Fungal Pathogens Causing Trunk and Branch Cankers of Almond Trees in Morocco

“…The fungus shows a large geographic distribution worldwide. For instance, it has been isolated from almond trees showing symptoms of band canker in California [13,25] and symptoms of dieback in turkey [45]. Further, the pathogenicity experience in this work revealed that the L. theobromae showed the highest virulence on almonds causing a longer lesion of an average of 280 mm; these results were close to previous studies.…”

“…In addition, dieback of scaffold branches and shoots through pruning wounds and damaged tissues were reported [12]. Cross section of infected tissues showed circular, irregular, or wedge-shaped necrosis, leading to the destruction of phloem and xylem tissues, and therefore, in the end, canker blocks the circulation of water and nutrients resulting in the death of bark and cambium [13]. In the recent past, numerous studies have been conducted on fungal trunk pathogens of fruit trees, such as stone and pome fruit trees [14][15][16], grapevine [17,18] pistachio [19,20], Ficus trees [21], blueberry [22] and olive [23].…”

The air mycobiome is decoupled from the soil mycobiome in the California San Joaquin Valley

“…Found primarily in California and Arizona, it remains unclear on what environmental medium Coccidioides primarily grows, its source of nutrition (Barker et al, 2012; Emmons, 1942; Kollath, Teixeira, et al, 2019; Taylor & Barker, 2019), or its precise means and range of dispersal (de Perio et al, 2019; Nicas, 2018; Pappagianis & Einstein, 1978; Schneider et al, 1997; Wilken et al, 2015). Agriculturally, the SJV is the most productive region in the United States (Food & Agriculture (CDFA), 2018), and plant pathogenic and parasitic fungi are responsible for significant losses in many of the chief crops grown therein (Baumgartner et al, 2019; Baumgartner & Rizzo, 2002; Camiletti et al, 2022; Holland et al, 2021). Determining the source and dispersal characteristics of airborne fungi can aid in preventing or mitigating fungal disease in humans and crops as well as offering a better understanding of fungal community ecology.…”

Phylogenomics of Plant-Associated Botryosphaeriaceae Species

“…Members of the Botryosphaeriaceae are probably most wellknown as being destructive blight and canker pathogens of planted hosts (Luo et al, 2019). In agricultural settings, for example, they infect a large number of fruit and nut crops, such as almond (Inderbitzin et al, 2010;Gramaje et al, 2012;Nouri et al, 2018;Holland et al, 2020), apple (Phillips et al, 2012), avocado (McDonald et al, 2009), citrus (Linaldeddu et al, 2015), grapevine (Urbez-Torres, 2011), olive (Úrbez-Torres et al, 2013), pistachio (Michailides, 1991;Nouri et al, 2019), and walnut . In forest plantations in Australia and South Africa, for example, they infect Eucalyptus spp.…”