Calonectria

Fungalpedia – Note 131 Calonectria

Calonectria De Not.

Citation when using this entry: Aumentado et al. in prep – Fungalpedia, plant pathogens. Mycosphere.

Index Fungorum, Facesoffungi, MycoBank, GenBank, Fig *.

Ascomycota, Pezizomycotina, Sordariomycetes, Hypocreomycetidae, Hypocreales, Nectriaceae

Calonectria was identified based on C. daldiniana (De notaris 1867). Species within this genus were previously known as Cylindrocladium for many years. However, Rossman et al. (2013) favored the use of the name Calonectria over Cylindrocladium, following its conservation by Hawksworth (2011) and McNeill et al. (2012). Most isolates were distinguished using morphological characteristics, such as macroconidial dimensions, septation, and vesicle shape, which are the mainly reliable traits for identifying Calonectria species (Li et al. 2017, Crous 2002, Schoch et al. 2000). For sexual morph identification, perithecial color, ascospore number, septation, and dimensions were also considered important (Lombard et al. 2010). However, due to the morphological similarity of perithecia, they were not found to be helpful in the identification process (Crous 2002, Crous & Wingfield 1994). The sexual morphs of Calonectria are characterized by their ascomata, which range in color from yellow to dark red and have scaly to warty walls. Additionally, they feature clavate asci with 4–8 spores. Asexual morphs of this genera display branched conidiophores, cylindrical and septate conidia, and stipe extensions with terminal vesicles. (Li et al. 2017, Lombard et al. 2010, 2016, Crous 2002).

Initial molecular studies used only the ITS gene to differentiate Cylindrocladium species but this contains limited useful characters (Crous et al. 1999, Schoch et al. 2001, Lombard et al. 2010). A more comprehensive phylogeny of the genera can be resolved by utilizing the internal transcribed spacer (ITS) region and 28S ribosomal RNA gene (LSU) for genus level; and employing combined β-tubulin (β-tub), translation elongation factor 1-alpha (tef1-α), calmodulin (cmdA), and histone-3 (his3) for species level (Jayawardena et al. 2019, Lombard et al. 2016, Crous et al. 2002). There are 433 species epithets in Index Fungorum (2023) under this genus. However, 314 species are currently accepted with molecular data (Pham et al. 2022, Sanchez-Gonzalez et al. 2022, Zhang et al. 2022, Liu et al. 2020, 2022, Mohali et al. 2021, Crous et al. 2021a, 2021b, Jayawardena et al. 2019).

Calonectria species are necrotrophic pathogens (Lombard et al. 2010) known to infect a broad range of plant species (Li et al. 2017, Chen et al. 2011, Lechat et al. 2010, Lombard et al. 2010, Crous 2002). They are primarily soil-borne pathogens of forestry, agricultural, and horticultural crops, affecting >100 plant families (Lopes et al. 2018, Li et al. 2017, Gehesquiére et al. 2016, Chen et al. 2011, Lombard et al. 2010, Crous 2002, Crous et al. 1991). Although they can cause fruit rot, they are more commonly associated with leaf spot and root rot (Lopes et al. 2018). Leaf spots caused by C. colhounii, C. ilicola, C. indusiata, and C. pteridis manifest as water-soaked lesions becoming tan to dark brown, appearing circular or uneven in shape, and encircled by a red, dark brown, or purple border with a chlorotic zone (Lombard et al. 2010, 2011). Root rot caused by C. crotalariae and C. ilicola primarily shows root necrosis, blackening, and splitting of the root cortex in conifers and blackening with longitudinal cracking in hardwoods. The lesions may merge, destroying the root. Furthermore, the crown infection can occur as root infection spreads, leading to stunting, foliage discoloration, defoliation, and eventually plant death (Lombard et al. 2010, 2011). Pathogenicity of Calonectria species (C. metrosideri, C. tunisiana, and C. foliicola) has been confirmed on Eucalyptus spp. (Lombard et al. 2016, Crous et al. 2019, Soares et al. 2019, Aiello et al. 2020, Liu et al. 2022), Serenoa repens with C. pteridis (Yang et al. 2014), and Hevea brasiliensis with C. foliicola (Thaochan et al. 2022). Calonectria ilicicola is pathogenic to Carica papaya and is extremely pathogenic to Acacia sp., Arachis sp., and various Eucalyptus spp., exhibiting its lack of host specificity (Nishijima & Aragaki 1973). Also, C. ilicicola causes root rot in Persea americana, resulting in decreased root biomass and a gradual reduction in plant height (Dann et al. 2012). Calonectria pseudonaviculata incites blight to Buxus spp. where it caused substantial losses in nurseries (Ivors et al 2012) and revealed the susceptibility of other plant species within Buxaceae viz., Sarcococca spp. (Henricot et al. 2008), Pachysandra procumbens, and P. terminalis (LaMondia et al. 2012, 2013).

Share This Item, Choose Your Platform!