Chocolate spot disease of Eucalyptus

Abstract

Chocolate Spot leaf disease of Eucalyptus is associated with several Heteroconium-like species of hyphomycetes that resemble Heteroconium s.str. in morphology. They differ, however, in their ecology, with the former being plant pathogenic, while Heteroconium s.str. is a genus of sooty moulds. Results of molecular analyses, inferred from DNA sequences of the large subunit (LSU) and internal transcribed spacers (ITS) region of nrDNA, delineated four Heteroconium-like species on Eucalyptus, namely H. eucalypti, H. kleinziense, Alysidiella parasitica, and one isolate resembling a novel species in a clade separate from the holotype of Heteroconium, H. citharexyli. Based on molecular phylogeny, morphology and ecology, the Heteroconium-like species associated with Chocolate Spot disease are reclassified in the genus Alysidiella, which is shown to have mycelium that is immersed in and superficial on the host tissue and conidiogenous cells that can have loci that are either inconspicuous or proliferating percurrently. Furthermore, conidiogenous cells can either occur solitary on hyphae, or be sporodochial, arranged on a weakly developed stroma, which further distinguishes Alysidiella from Heteroconium.

Fungal Planet description sheets: 469-557

“…Notes — The genus Blastacervulus is monotypic, based on B. eucalypti ( Swart 1988 ). Blastacervulus eucalypti is closely related to Aulagraphina eucalypti and Alysidiella species, with all three genera causing ‘chocolate spot’ disease on Eucalyptus ( Cheewangkoon et al 2012 ). Blastacervulus eucalyptorum can be distinguished from B. eucalypti (aseptate conidia (4–)6–7(–8) × (4–)5–6 μm) in having larger, 1- and 2-septate conidia (Giraldo et al in prep.).…”

The Genera of Fungi—G3: Aleurocystis, Blastacervulus, Clypeophysalospora, Licrostroma, Neohendersonia and Spumatoria

“…Blastacervulus eucalypti is closely related with Aulographina eucalypti and Alysidiella species (Fig. 1), all of them associated with target spot and chocolate spot disease on Eucalyptus, respectively (Cheewangkoon et al 2012).…”

Blastacervulus Metrosideri Sp. Nov . Leaf Spot on Metrosideros Excelsa in New Zealand

“…A leaf-spotting fungus common on Metrosideros excelsa (pohutukawa, Myrtaceae) in New Zealand is morphologically similar to a number of leaf-spotting fungi on another myrtaceous host, Eucalyptus. These fungi on Eucalyptus leaves have been placed in a range of genera, including Alysidiella, Blastacervulus, and Staninwardia (Swart 1988, Sutton 1971, Summerell et al 2006, Cheewangkoon et al 2012, and collectively the diseases they cause on Eucalyptus have sometimes been referred to as chocolate spot (e.g. Cheewangkoon et al 2012;Crous et al 2016).…”

“…These fungi on Eucalyptus leaves have been placed in a range of genera, including Alysidiella, Blastacervulus, and Staninwardia (Swart 1988, Sutton 1971, Summerell et al 2006, Cheewangkoon et al 2012, and collectively the diseases they cause on Eucalyptus have sometimes been referred to as chocolate spot (e.g. Cheewangkoon et al 2012;Crous et al 2016). Cheewangkoon et al (2012) presented a phylogeny that resolves a clade of closely-related species of Eucalyptus chocolate-spot leaf pathogens that they refer to the genera Blastacervulus, Alysidiella and Aulographina.…”

“…Cheewangkoon et al 2012;Crous et al 2016). Cheewangkoon et al (2012) presented a phylogeny that resolves a clade of closely-related species of Eucalyptus chocolate-spot leaf pathogens that they refer to the genera Blastacervulus, Alysidiella and Aulographina. These taxa form a well-resolved clade, and were placed in the Asterinaceae by Giraldo et al (2017).…”