S14 - Session P5 - Detection and characterization of pests and diseases III - Fungal organisms constituting sooty mould on cool-stored ‘Zesy002’ and ‘Hayward’ kiwifruit in New Zealand

Authors: Simone Blackwood *,

Seona Casonato, Eirian Jones, David Logan, Monika Walter

Sooty mould is a universally accepted name to describe the complex of superficial, Ascomycota fungi that grow upon the honeydew exudates of Hemiptera. Over 200 foliar epiphytes can contribute towards sooty mould, forming a network of black mycelia on the surfaces of affected plant material. Actinidia (kiwifruit) is an economically important crop in New Zealand affected by sooty mould due to the honeydew excretions by Scolypopa australis (passionvine hopper). In the 2018/19 kiwifruit season, S. australis was responsible for $44 million in economic loss due to sooty mould, making it a substantial issue for the industry. This fungal complex has not been studied in Actinidia crops, nor has sustainable and effective control been achieved. This research investigates the fungi responsible for sooty mould communities upon Hayward and Gold3 kiwifruit varieties in New Zealand and composition changes during post-harvest cool storage. Kiwifruit infected by sooty mould were harvested from an orchard in June 2021 and stored for six months at 1°C. Fungal communities were analysed at three-time points; prior to storage and after three and six months in storage. To represent the various nutritional niches of fungi, cultures were taken from the lenticels, skin and flesh of kiwifruit. Samples were grown on potato dextrose agar (PDA) under controlled conditions, morphotyped and identified to the genus level using DNA sequencing. The fungal communities constituting sooty mould of kiwifruit differed between Gold3 and Hayward varieties. Additionally, the community composition of sooty mould changed as time increased in cool storage through new and different genera. This research will inform innovative and sustainable control strategies against sooty mould. Novel biological control agents can be introduced targeted at fungal communities on the kiwifruit variety of interest. In combination with current insect management, this will reduce sooty mould incidence in orchards and prevent further losses.