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Biological control of Botrytis spp. by Ulocladium atrum through competitive colonisation of necrotic plant tissues Jürgen Köhl Biological control of Botrytis spp. by Ulocladium atrum through competitive colonisation of necrotic plant tissues Jürgen Köhl Wageningen, April 2004 © 2004 Wageningen, Plant Research International B.V. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior written permission of Plant Research International B.V. Plant Research International B.V. Address : Droevendaalsesteeg 1, Wageningen, The Netherlands P.O. Box 16, 6700 AA Wageningen, The Netherlands Tel. : +31 317 47 70 00 Fax : +31 317 41 80 94 E-mail : [email protected] Internet : http://www.plant.wageningen-ur Table of contents Table of contents PREFACE SUMMARY 1 INTRODUCTION........................................................................ 1 1.1 Microbial suppression of colonisation of necrotic tissues by necrotrophic fungal foliar pathogens.............................................3 1.1.1 Biology of necrotrophic pathogens.............................................................. 3 1.1.2 Ecological niche characteristics ................................................................... 6 1.1.3 Antagonists attributes .................................................................................... 7 1.1.4 Biological control through microbial suppression of pathogen colonisation of necrotic tissues and subsequent sporulation.................14 1.1.5 Conclusions ...................................................................................................21 1.2 Selection, characteristics and use of Ulocladium atrum in biocontrol of Botrytis spp. in necrotic tissues ............................. 22 1.2.1 Role of necrotic tissues in Botrytis epidemics............................................23 1.2.2 Antagonist screening....................................................................................24 1.2.3 Effect of environmental factors on U. atrum............................................25 1.2.4 Mode of action of U. atrum .........................................................................27 1.2.5 Use of U. atrum for disease control in crops.............................................28 2 MATERIAL AND METHODS................................................... 33 2.1 Materials....................................................................................... 35 2.2 Methods........................................................................................ 36 2.2.1 Role of necrotic tissues in Botrytis epidemics............................................36 2.2.2 Antagonist screening....................................................................................43 2.2.3 Effect of environmental factors on U. atrum............................................49 2.2.4 Mode of action of U. atrum .........................................................................62 2.2.5 Use of U. atrum for disease control in crops.............................................67 3 RESULTS..................................................................................... 79 3.1 Role of necrotic tissues in Botrytis epidemics............................ 81 3.1.1 Botrytis leaf spot in onion .............................................................................81 3.1.2 Botrytis grey mould in annual strawberries.................................................84 3.1.3 Botrytis grey mould in cyclamen ..................................................................88 Biological control of Botrytis spp. with Ulocladium atrum 3.2 Antagonist screening.................................................................... 89 3.2.1 Screening on necrotic onion leaves under controlled conditions..........89 3.2.2 Screening on field exposed necrotic lily leaves.........................................97 3.3 Effect of environmental factors on U. atrum ..............................105 3.3.1 Effect of temperature on conidial germination and mycelial growth of U. atrum in comparison with Gliocladium spp. ......................105 3.3.2 Effect of water potential on conidial germination of U. atrum............109 3.3.3 Effect of temperature on antagonism of U. atrum against B. cinerea and B. aclada on necrotic leaf tissues........................................................115 3.3.4 Effect of water potential on antagonism of U. atrum against B. cinerea on cyclamen leaves .....................................................................................118 3.3.5 Persistence of U. atrum conidia on green leaves and subsequent com- petitive colonisation of senesced leaves by B. cinerea and U. atrum......119 3.4 Mode of action of U. atrum.........................................................135 3.4.1 Fungal interactions: microscopical and ultra-structural studies...........135 3.4.2 Competitive substrate colonisation: experimental studies and simulation modelling..................................................................................142 3.5 Use of U. atrum for disease control in crops ..............................146 3.5.1 Experiments in strawberries......................................................................146 3.5.2 Experiments in onion ................................................................................151 3.5.3 Experiments in cyclamen under commercial growing conditions ......155 3.5.4 Experiments in Pelargonium........................................................................163 3.5.5 Experiments in pot roses...........................................................................173 4 DISCUSSION .............................................................................177 4.1 Introduction ................................................................................179 4.2 Role of necrotic tissues in Botrytis epidemics............................180 4.3 Antagonist screening...................................................................183 4.4 Effect of environmental factors on U. atrum.................................188 4.4.1 Temperature ................................................................................................188 4.4.2 Water potential............................................................................................191 4.4.3 Persistence of conidia ................................................................................194 Table of contents 4.5 Mode of action of U. atrum.........................................................198 4.5.1 Fungal interactions: microscopical and ultra-structural studies...........198 4.5.2 Competitive substrate colonisation: experimental studies and simulation modelling..................................................................................200 4.6 Use of U. atrum for disease control in crops ............................. 202 4.6.1 Strawberries .................................................................................................202 4.6.2 Onion ...........................................................................................................203 4.6.3 Cyclamen......................................................................................................204 4.6.4 Pelargonium ....................................................................................................205 4.6.5 Pot roses.......................................................................................................207 4.6.6 Other crops or diseases .............................................................................208 4.7 Perspectives for development of a biocontrol agent based on U. atrum ................................................................................ 209 5 LITERATURE CITED ..............................................................213 Preface Preface In this book an attempt is made to discuss concept development for biological control of necrotrophic fungal foliar pathogens and to summarise results obtained in research on the selection, characterisation and use of the antagonist Ulocladium atrum in biocontrol of Botrytis spp. in necrotic plant tissues. This research has been carried out during the period 1990-2001 at the DLO Research Institute for Plant Protection (IPO-DLO), merged into Plant Research International in 2000, in Wageningen, the Netherlands. The main results presented in the book have been published earlier in a series of publications in scientific journals or book chapters as listed below. All authors of publications contributed significantly to the progress made in the different research steps. The book has been presented as thesis of postdoctoral lecturing qualification (Habilitationsschrift) at the faculty of agriculture of the Rheinische Friedrich- Wilhelms-Universität in Bonn, Germany, which has been accepted in December 2003. Substantial funding from different sources allowed the continuation of research on concept development, antagonist screening and antagonist testing in different crop- ping systems. The main funding sources during the period 1990-2001 were: Dutch Ministry of Agriculture, Nature Management, and Fisheries (1990 - 2001); European Commission (FAIR3 PL96-1898 BIOSPORSUPPRESS (1996 - 2001); Dutch Product Board for Horticulture (Produktschap Tuinbouw) (1996 - 2000); Technology Foundation (STW) for G.J.T. Kessel (1995 - 1999); International Agricultural

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