Studies on potential antagonists for 'Fusarium pseudograminearum' displacement from cereal stubble for crown rot management

Abstract

'Fusarium pseudograminearum' (Fp) is a stubble-borne fungus that causes crown rot in wheat. The aim of this project was to determine the effects of abiotic and nutritional factors on displacement of Fp from stubble by potential antagonists. Fungi from stubble were screened for their antagonistic ability against Fp. 'Trichoderma harzianum' (Th), 'Fusarium nygamai' (Fn), and 'F. equiseti' (Fe) which were antagonistic and 'Alternaria infectoria' (Ai) which was the most commonly found fungus in stubble, were included in experimental work. An assay for displacement of Fp from straw by potential antagonists based on a 0-4 scale was a sensitive research tool that could detect changes over short periods of time. There were significant interactions between temperature and water potential in their effects on Fp displacement from straw by antagonists. Th gave best Fp displacement from straw in hot wet conditions whereas Fe and Fn were moderate displacers at cool dry conditions. Index of dominance in dual culture in higher categories was fairly consistent with displacement patterns and was a highly sensitive technique. The effect of wetting and drying cycles on Fp displacement by antagonists could not be determined satisfactorily but a relationship between rainfall and temperature (rainday heatsums) gave a good correlation of displacement with environmental factors, Low temperature tolerance will be more important in selection of antagonists above ground and low water potential tolerance below ground. Fusarium spp. utilized similar carbon sources, suggesting competition for substrates. The role of nitrogen in resource utilisation for relative growth, dual culture and antagonism was studied.