Host range investigation of Phoma koolunga, a causal agent of ascochyta blight of field pea
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ORIGINAL PAPER
Host range investigation of Phoma koolunga, a causal agent of ascochyta blight of field pea E. C. Keirnan 1 & J. A. Davidson 1,2 & R. L. Correll 3 & E. S. Scott 1 Received: 18 March 2020 / Accepted: 17 September 2020 / Published online: 1 October 2020 # Australasian Plant Pathology Society Inc. 2020
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. Keywords Pisum sativum . Disease incidence . Disease severity . Australian native legumes
Introduction Field pea (Pisum sativum L.) is thought to have been introduced into Australia in the late nineteenth century and was grown with other winter pulse crops on a limited scale until the 1980s, when planting increased as improved varieties became available (Siddique et al. 2013). Ascochyta blight (synonym: blackspot) was first recorded in Australian field pea crops in the 1960s (Ali and Dennis 1992). Ascochyta blight is a serious, globally distributed, primarily foliar disease of field pea. In Australia, it is associated with grain yield loss * E. S. Scott [email protected] 1
School of Agriculture, Food and Wine, Waite Research Institute, The University of Adelaide, Adelaide, South Australia 5005, Australia
2
South Australian Research and Development Institute (SARDI), Adelaide, South Australia 5001, Australia
3
Rho Environmetrics, PO Box 366, Highgate, South Australia 5063, Australia
of 15 to 75% in individual crops (Bretag et al. 1995, 2006; McMurray et al. 2011). Ascochyta blight may be caused by a combination of up to four fungal spec
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