Poster: Diseases of Plants: New & Emerging Diseases

564-P

Multiple Pestalotiopsis and Neopestalotiopsis species cause flower bight of macadamia in Australia
O. AKINSANMI (1), S. Nisa (1), O. Jeff-Ego (1), A. Drenth (2) (1) University of Queensland, Brisbane, Australia; (2) University of Queensland, , Australia

Incidence of ‘dry flower’ the disease, has been increasing and now occurs in different production regions in Queensland and New South Wales, Australia. Although yield losses range between 10% and 30%, total crop failures have occurred in certain cultivars. Therefore, this study examined the etiology of the disease in Australia. Results from a survey of over 240 macadamia racemes in different orchards in Australia revealed that all the four developmental stages of macadamia racemes including the florets and the rachis were affected. Several fungi genera including Alternaria, Epicoccum, Fusarium, Botrytis, Cladosporium, Penicillium, Aspergillus and Diaporthe were obtained from tissue samples, however, their occurrence was irregular between samples and significantly (P <0.05) less than Pestalotiopsis -like isolates, which constituted 41% of the total isolates. Based on the concatenated partial sequence of three gene loci (Internal transcribed spacer, β-tubulin and translation elongation factor 1-alpha) the phylogenectic analysis of 32 Pestalotiopsis -like isolates showed they formed two novel taxa in the Neopestalotiopsis and Pestalotiopsis genera. The grouping of the isolates was regardless of location or plant part. Koch’s postulates were confirmed with the different Neopestalotiopsis and Pestalotiopsis species and this is the first report of these two genera as causal agents of raceme blight of macadamia.