Phytophthoranicotiana evar .nicotiana e ontomatoe s G. Weststeijn rt i NN08201,541 ^ G. Weststeijn Phytophthoranicotiana evar .nicotiana e ontomatoe s Proefschrift ter verkrijging van de graad van doctor in de landbouwwetenschappen, op gezag van de rector magnificus, prof. dr. ir. H. A. Leniger, hoogleraar in de technologie, in het openbaar te verdedigen op vrijdag 2 februari 1973 des namiddags te vier uur in de aula van de Landbouwhogeschool te Wageningen STELLINGEN I Bijhe tonderzoe k naar debestrijdingsmogelijkhede n van bodempathogenen behorend tot de familie van dePythiaceae is tot nu toe onvoldoende aandacht geschonken aan dero lva nd ezoospore n bijhe tziekteproce s ind egrond . II De conclusie van Ho, dat Phytophthora megasperma Drechsler var. sojae Hildebrand in de grond hoogstwaarschijnlijk in ziek sojaboonweefsel overblijft, is niet geiecht- vaardigd. Ho,H . H., Mycologia 61(1969 )835-838 . Ill De invloed van de groeiomstandigheden op de lengte-breedte-verhouding van de sporangien van Phytophthora palmivora(Butl. ) Butl. is onvoldoendeonderzoch t om dezeeigenscha p tegebruike n voor eentaxonomisch e onderverdelingva nd eschimmel . Turner, P.D. ,Trans.Br.mycol .Soc .4 3(1960 )665-672 . IV Het onderzoek naar de invloed van uitwendige omstandigheden op de groei van groentegewassen ondergla smoe tmee rgerich tzij n opd emogelijkhede n tot bestrijding vanziekte nda n opdi eto t vermeerderingva nd ekilogramopbrengst . V Bij de bestudering van de invloed van luchttemperatuurwisselingen op de groei van groentegewassen wordt te weinig rekening gehouden met het daardoor veroorzaakte verloopva nd egrondtemperatuur . Hussey,G. ,J .exp .Bot . 16(1965 )373-385 . VI Het is verwarrend in de mycologie de term 'vegetatief te gebruiken, als daaraan een anderebetekeni sword tgehech tda ni nd ebotanie . Ainsworlh,G . C, 1967.Dictionar y offungi . CMI, London. Burnett,J . H., 1967. Fundamentals ofmycology .Edw .Arnol d (Publ.), London. VII Ter bevordering van de internationale communicatie in de fytopathologie dienen ge- lijksoortige termen afgeleid van eenzelfde stam in de verschillende talen op dezelfde maniergedefinieer d te worden. Dit vereist de instelling van een internationale werk- groepvoo rd eterminologi ei nd e fytopathologie. VIII Bij de opstelling van een kostenbegroting voor oogstwerktuigen in de akkerbouw mogen de gevolgen van het te verwachten struktuurbederf van de grond niet buiten beschouwing gelatenworden . IX Inhe tNederlands eInternational e Hulpprogrammamoe td eopleidin gva n middelbaar personeel in de ontwikkelingslanden voor diensten in de landbouwsector een belang- rijker plaatsinneme n danhede nhe tgeva lis . X • Niet alleen uit esthetische maar ook uit volksgezondheidsoverwegingen moet het stedelijk openbaar groen zodanig worden ingedeeld, dat gazons en speelplaatsen vrij blijvenva n hondenfaeces. XI De mogelijkheid, die in artikel 1639n van het Burgerlijk Wetboek gegeven is om een dienstbetrekking tebeeindige n voor het verstrijken van dewettelijkvastgesteldeproef- tijd zonder inachtnemingva n devoo r deopzeggin g geldende bepalingen, gaatvoorb y aanhe tnu t voor allebelanghebbend e partijen derede nva nd ebeeindigin gt eweten . Proefschrift vanG . Weststeijn Wageningen,2 februar i 1973 Contents I. Introduction 1 II. The cultureo f tomatoes 2 1. In the Netherlands 2 A. Soil disinfection 2 B. Sowing and propagation 2 C. Period of planting 3 D. Planting and watering 3 E. Temperatures after planting 3 F. Pest and disease control 3 G. Duration of the crop 4 2. In Southern England and Guernsey 4 III. Thediseas e 5 1. Symptoms 5 A. Foot and root rot 5 B. Leaf blight 5 C. Leaf stalk and stem infection 6 D. Fruit rot 7 2. Closely similar diseases abroad and their respective pathogens 7 3. Isolations from the Netherlands 8 4. Comparison with the disease caused by P.infestans (Mont.) de Bary 9 A. Symptoms 9 B. Epidemiological aspects 13 5. Discussion 13 IV. Thepathoge n 15 1. Studies in vitro 15 A. Culture media 15 B. Addition of antibiotics 16 C. Temperature 18 D. Formation of sporangia 18 2. Isolation methods 21 A. Isolation from plant tissue 21 B. Trapping from soil 21 3. Pathogenicity 22 4. Discussion 23 V. Persistence of thepathoge ni nsoi l 25 1. Literature 25 2. Experiments 26 VI. Infection during propagation 29 1. Introduction 29 2. Sources of root and foot infection 29 A. Sowing compost and seedlings 2" B. Soil of propagation beds 30 3. Build-up of inoculum in the soil 30 4. Incubation period in relation to age of the host 31 5. Stem infection through leaves 32 6. Discussion and conclusions VII. Influence of soil temperature and soil moisture 34 1. Literature 34. 2. Materials and methods 36 3. Soil temperature 37 4. Soil moisture 42 5. Soil temperature and moisture in relation to stem base rot 43 6. Discussion VIII. Influence of nitrogen and potassium nutrition of the host 45 45 1. Introduction 45 2. Literature 46 3. Materials and methods 47 4. Experiments 47 A. NK-experiment in white peat 48 B. N-experiments in liquid media 50 C. K-experiments in liquid media 52 5. Discussion IX. Control 54 1. Introduction 2. Root infection A. Soil treatment before planting Al. Soil treatment by heat ^ CO A2. Soil treatment by disinfectants B. Soil treatment at and after planting ^ Bl. Materials and methods ^ B2. Effect of fungicides on disease development 60 B3. Duration of the antifungal effect in the soil 62 B4. Phytotoxicity 63 B5. Application methods ^3 3. Stem base infection 64 4. Infection of aerial parts after planting 65 5. Infection of planting material 66 A. Leaf and stem infection 66 B. Root infection 66 6. Resistance 67 A. Literature 67 B. Experiments 67 7. Evaluation and discussion 69 X. General discussion 72 1. Incidence of root infection in the Netherlands 72 2. Phytophthora root rot in England and Guernsey 73 Summary , 75 Samenvatting 77 Acknowledgments 80 References 81 I. Introduction In the last twenty years glasshouse tomato production in the Netherlands increased from 75.000 tons in 1950t o 200.000 tons ten years later and to 379.000 tons in 1970. The acreage increased from 1110h a in 1950t o 2589 ha in 1960an d 3464h a in 1965, remaining approximately at that level until the present time (3339 ha in 1970). The rise in production during thefirstmentioned decenniu m was largely obtained by the increasei n acreage,bu t during the second decennium there was a considerable risei n productivity per unit area. This resulted from intensification of production methods, by the construction of glasshouses with better lighttransmissibility , by improvement of the heating and ventilation systems, of the irrigation and dressing methods and of soil disinfection. Also, the propagation of better plant material concentrated to a greater extent than before on specialised holdings, the rise of temperatures during propagation and after transplanting and extensive application of carbon dioxide contributed to theimprovemen t of productivity. Thesechanges ,especiall y thoseconcernin g propagation and the temperatures used, have had an important influence on the incidence of diseases, such as root and foot rots. These diseases,whic h havealway s occurred on tomato in the Netherlands, were knownt ob ecause db yth efung i Rhizoctoniasolani Kiihn ,Botrytis cinerea Pers .e xFr . and Didymella lycopersici Kleb. (Riemens, 1939; Fremouw, 1940; Verhoeff, 1963a and 1963b). A different typeo f root and foot rot which wasno t caused by any of the pathogens mentioned abovewa sfoun d in 1963. Verhoeff and De Mos (1963)considere d it to be of a physiological nature. Furthermore, an aberrant type of stembase rot, appearing within a few days after transplanting in June and July, had been reported from 1959 onwards, which was also thought to be a physiogenic disorder (Anonymous, 1959; De Boer, 1960).Thes e two 'physiological' disorders gradually increased in frequency and reached epidemic proportions in 1966an d 1967.I t was therefore decided to start a special research project at the Glasshouse Crops Research and Experiment Station at Naaldwijk toinvestigat e these problems. The studieswer eaimin g to find: a. the cause of the disease; b. the conditions which enhance its incidence; c. the ways of prevention or control. II. Thecultur eo f tomatoes 1. In theNetherland s Several ways of tomato-growing can be distinguished: a. planted in winter in fully heated glasshouses; b. planted in springtime in slightly and non-heated glasshouses and c. planted in summer without heating followed by heating in autumn. The crop in the open air is not mentioned, as this way of growing on a commercial scale has beenabandone d inth eNetherlands . Below,cultivatio n methods and theirhistor y are described briefly, asthe yma yhav e or haveha d aninfluenc e on thedevelopmen t of the diseasereporte d here. Cultivation canb edivide dint otw oseparat ephases ;thes eare :a . thepreplantin gperiod ,includin g preparation of the soil, sowing and propagation of the plant material and b. the planting and post-planting period including all work from planting until the end of the crpp,suc h as planting,managemen t of soil and air conditions,tendin g of plants, diseasean dpes tcontrol ,harvestin getc . A. Soil disinfection During the last ten years annual soil disinfection in summer or autumn has become general practice. Previously, steam was used and introduced into the soil through dug-in pipes or chloropicrin was applied. To reduce labour costs, however, pipe steaming was replaced by sheet steaming; besides, methyl bromide became available as soil disinfectant. If root-knot nematodes only are present in the preceding crop, the soili streate d solely with a nematicide. For summer planting alone the soil isno t disinfected, becauseth ecost sar eto o high in comparison with the modest revenueso f anautum ncrop . B. Sowingandpropagation For small quantities seeds are sown in special sowing compost arranged in sowing boxesan d for larger quantities in sowingbed seithe r elevated asbenche s or at ground level.