Host range investigation of Phoma koolunga, a causal agent of ascochyta blight of field pea

Abstract

Phoma koolunga is one of three species that cause ascochyta blight (synonym: blackspot) of field pea (Pisum sativum L.) in Australia. P. koolunga was first described in 2009 in South Australia and has since been reported in Western Australia and Victoria. However, the origin of the pathogen and its host range remain largely unknown. The aim of this study was to examine the host range of P. koolunga and to explore possible origin(s) of P. koolunga as a pathogen of field pea in Australia. Host range experiments were conducted in a growth room using 41 legumes comprising Australian native, naturalised, crop and pasture legumes, and wild type Pisum, Lathyrus and Vicia spp. Two isolates of P. koolunga from field pea in South Australia were compared. Disease incidence and severity were measured as number of leaves and percentage of leaf area diseased every 4 days up to 12 days post-inoculation. All legumes tested, except Cicer arietinum (chickpea), developed leaf lesions and some also had stem lesions. Disease incidence and severity differed significantly among species but not consistently between the P. koolunga isolates. The ability of the isolates to cause lesions on a wide range of legumes in controlled environment conditions suggests the fungus has a broad host range in humid and mild temperature conditions conducive for disease development. These results provide no evidence to suggest P. koolunga could have evolved with any of the 17 Australian native legume species tested and the fungus is, therefore, unlikely to have originated within Australia.

De Novo Long-Read Whole-Genome Assemblies and the Comparative Pan-Genome Analysis of Ascochyta Blight Pathogens Affecting Field Pea

“…An increased host range is equally proportional to the diversity of CAZymes in the fungal genome, as has been described for Macrophomina phaseolina (Islam MS, et al, 2012). The large CAZyme repertoire for the AB species suggests a broad host range, which is in congruence with host specificity experiments carried out for the species [ 167 , 168 , 169 , 170 ].…”

Overview of Phoma-Like Fungi on Important Legumes (Papilionaceous Plants)

“…All legumes tested, except Cicer arietinum (chickpea), developed leaf lesions and some also had stem lesions. Disease incidence and severity differed significantly among species but not consistently between the P. koolunga isolates (Keirnan et al 2020).…”

Ascochyta blight in North Dakota field pea: the pathogen complex and its fungicide sensitivity

“…exigua ( Li et al., 2012 ), and Phoma glomerata ( Tran et al., 2014 ) are associated with the disease complex, also known as black spot of field pea in Australia. P. koolunga has been widely distributed in Australia and has become an important component of the Ascochyta blight complex of field pea ( Davidson et al., 2012 ; Tran et al., 2014 ; Keirnan et al., 2020 ).…”