Phylogeny, Morphology, Distribution, and Pathogenicity of Botryosphaeriaceae and Diaporthaceae from English Walnut in California

Abstract

Species of family Botryosphaeriaceae and genus Diaporthe (anamorph: genus Phomopsis, family Diaporthaceae) were reported and caused diseases on various fruit and nut trees in California. In the last several years, diseases on English walnut (Juglans regia) caused by species of Botryosphaeriaceae and Diaporthe were observed frequently in California. Disease symptoms include stem canker; shoot canker and blight; twig, leaf, and fruit blight; and necrotic leaf lesions. Isolates of the pathogen were collected from English walnut in 13 counties in California. The aims of this study were to identify these isolates and to test their pathogenicity to English walnut cultivars. In total, 159 California isolates were identified based on comparisons of DNA sequence data of the internal transcribed spacer, translation elongation factor 1-α, and β-tubulin gene regions, and combined with the morphological features of the cultures and conidia. Research results revealed that isolates represent 10 species of Botryosphaeriaceae and two species of Diaporthe. These species include Botryosphaeria dothidea, Diplodia mutila, D. seriata, Dothiorella iberica, Lasiodiplodia citricola, Neofusicoccum mediterraneum, N. nonquaesitum, N. parvum, N. vitifusiforme, Neoscytalidium dimidiatum, Diaporthe neotheicola, and D. rhusicola. Pathogenicity on three English walnut cultivars (‘Chandler’, ‘Tulare’, and ‘Vina’) using a mycelium plug inoculation method revealed that all these species are pathogenic to all the tested cultivars, with L. citricola and N. parvum being the most pathogenic species, followed by N. mediterraneum, N. dimidiatum, and B. dothidea. Chandler was more tolerant to infection than Tulare and Vina. Results in this study determined that multiple numbers of the Botryosphaeriaceae fungi and two Diaporthe spp. cause cankers and blights of English walnut and vary in their virulence from highly to slightly virulent, respectively.

Identification and distribution of Botryosphaeriaceae species associated with blueberry stem blight in China

“…3c, f) (Table 3). All these characteristics were consistent with the description of B. dothidea (Slippers et al 2004;Wright and Harmon 2010;Chen et al 2014). …”

“…This was likely because of our use of a more susceptible cultivar Bluecrop. L. theobromae and N. parvum have been previously reported to be highly virulent species in many other hosts in tropical and subtropical regions (Marques et al 2013;Chen et al 2014). Pathogenicity of L. theobromae and N. parvum has been well studied on fruit trees and other woody hosts in China and worldwide recently, including syzygium (Pavlic et al 2007), peach (Wang et al 2011), grapevine (Yan et al 2013;Úrbez et al 2008), pear (Zhai et al 2014), almond (Chen et al 2013), mango (Marques et al 2013), walnut ) and citrus (Adesemoye et al 2014).…”

“…Morphological characterization Botryosphaeriaceae isolates from diseased blueberry twigs and woody tissues were first identified based on colony morphology and conidial characteristics by comparing with previous studies (Phillips 2002;Slippers et al 2004;Alves et al 2008;Espinoza et al 2009;Wright and Harmon 2010;Marques et al 2013;Chen et al 2014). All purified isolates for colony morphology characterization were grown on PDA in the dark at 25°C, including eight isolates selected to conduct a temperature experiment.…”

“…Fungi in the family Botryosphaeriaceae have a wide geographical distribution and several species cause diseases on a large number of woody hosts (Barr 1987;Chen et al 2014). In China, Botryosphaeriaceae species cause diseases on many important fruit crops such as apple (Tang et al 2012), grapevine (Yan et al 2013), pear (Zhai et al 2014), and peach (Wang et al 2011).…”

Fungal trunk pathogens associated with wood decay of pistachio trees in Iran

“…Recently, B. dothidea has been isolated and reported from pistachio trees showing panicle blight in Iran (Mohammadi et al, 2015). Neofusicoccum parvum has been isolated from pome and stone fruit trees in South Africa , from avocado in California (McDonald et al, 2009), from almond (Inderbitzin et al, 2010), English walnut (Chen et al, 2014a), and grapevine in California (Úrbez-Torres & Gubler, 2009). In Iran, both species have been isolated from cypress and grapevine (Arabnezhad & Mohammadi, 2012;Mohammadi et al, 2013b).…”