Luteocirrhus shearii gen. sp. nov. (Diaporthales, Cryphonectriaceae) pathogenic to Proteaceae in the South Western Australian Floristic Region.

Colin Crane,Treena I Burgess

doi:10.5598/imafungus.2013.04.01.11

Abstract

Morphological and DNA sequence characteristics of a pathogenic fungus isolated from branch cankers in Proteaceae of the South West Australian Floristic Region elucidated a new genus and species within Cryphonectriaceae (Diaporthales). The pathogen has been isolated from canker lesions in several Banksia species and Lambertia echinata subsp. citrina, and is associated with a serious decline of the rare B. verticillata. Lack of orange pigment in all observed structures except cirrhi, combined with pulvinate to globose black semi-immersed conidiomata with paraphyses, distinguishes the canker fungus from other genera of Cryphonectriaceae. This was confirmed by DNA sequence analysis of the ITS regions, β-tubulin, and LSU genes. The fungus (sexual morph unknown) is described as Luteocirrhus shearii gen. sp. nov. Lesions in seedlings of Banksia spp. following wound inoculation and subsequent recovery confirm Koch's postulates for pathogenicity. This pathogen of native Proteaceae is currently an emerging threat, particularly toward B. baxteri and B. verticillata.

Highlights

In a previous study of twig and branch cankers in Banksia coccinea, Shearer et al (1995) isolated several pathogens including a purported Zythiostroma sp. (IMI 336153)
Based on GenBank searches this undescribed species grouped within Cryphonectriaceae, and its taxonomic status, needs to be revised as Zythiostroma resides in Nectriaceae and not Cryphonectriaceae
Ninety-two isolates were collected from cankered branches of Banksia baxteri, B. coccinea, B. grandis, B. ilicifolia, B. littoralis, B. pteridifolia, B. quercifolia, B. sessilis, B. speciosa, B. sphaerocarpa, B. verticillata, and Lambertia echinata subsp. citrina across the South West Australian Floristic Region (SWAFR)

Summary

Introduction

In a previous study of twig and branch cankers in Banksia coccinea, Shearer et al (1995) isolated several pathogens including a purported Zythiostroma sp. (IMI 336153). In a previous study of twig and branch cankers in Banksia coccinea, Shearer et al (1995) isolated several pathogens including a purported Zythiostroma sp. Recent studies on the causal agents of severe canker disease affecting Banksia communities and Lambertia spp. across the South West Australian Floristic Region (SWAFR) consistently returned Neofusicoccum australe, N. macroclavatum, and Cryptodiaporthe melanocraspeda, along with an undescribed species (Crane et al 2012) which shared morphology and ITS sequences with the purported Zythiostroma sp. Species of Cryphonectriaceae living within the bark and wood of trees have a worldwide distribution, include some of the world’s most important pathogens of trees, such as chestnut blight (Cryphonectria parasitica) and serious canker diseases of plantation eucalypts (Gryzenhout et al 2009). One species in each of the recognised genera within the family are virulent pathogens, while the remainder are either facultative parasites or saprophytes (Gryzenhout et al 2009)

Methods

Results

Conclusion