595.132:591.54:591,9(492)(87) MEDEDELINGEN LANDBOUWHOGESCHOOL WAGENINGEN • NEDERLAND • 70-2 (1970) CLIMATIC INFLUENCE ON THE DISTRIBUTION PATTERN OF PLANT PARASITIC AND SOIL INHABITING NEMATODES F. DAO D. Laboratory of Nematology, State Agricultural University, Wageningen, The Netherlands (Received 14-10-1969) H.VEENMA N & ZONEN N.V.- WAGENINGEN - 1970 Mededelingen Landbouwhogeschool Wageningen 70-2 (1970) (Communications Agricultural University) isals opublishe d as a thesis CONTENTS CHAPTER 1. GENERAL INTRODUCTION AND LITERATURE REVIEW . ... 1 1.1. General introduction 1 1.2. Published faunistic inventories 3 1.2.1. Initial surveys 4 1.2.2. Zoological surveys andexpedition s 6 1.2.3. Inventories for agricultural purposes 16 1.3. Thenematode' s environment 23 1.3.1. A nematode population inrelatio n to itsenvironmen t 24 1.3.2. Climate and weather 27 1.3.3. Temperature 28 1.4. Scope of theinvestigation s 35 CHAPTER 2. MATERIALS AND METHODS 36 2.1. Sampling techniques 36 2.2. Nematodes 37 2.3. Plants, soils and containers 38 2.4. Temperature equipment 38 2.5. Estimation of nematode densities and infestation levels 39 2.5.1. Soils 39 2.5.2. Plant tissues and agar cultures 39 2.6. Statistical treatment of thedat a 40 CHAPTER 3. ANALYSIS OF THE NEMATOFAUNAS IN VENEZUELA AND THE NETHERLANDS 41 3.1. Introduction 41 3.2. Nematodes in Venezuela 42 3.3. Nematodes in theNetherland s 50 3.4. Discussion 50 CHAPTER 4. TRANSMISSION AND INOCULATION EXPERIMENTS 53 4.1. Introduction 53 4.2. Inoculation experiments inVenezuel a 54 4.3. Transmission experiments inVenezuel a 56 4.4. Transmission experiments inth eNetherland s 56 4.5. Discussion 58 CHAPTER 5. AIR PRESSURE EFFECTS 60 5.1. Introduction 60 5.2. Aphelenchus avenae (V)an d (N) 60 5.3. Ditylenchus dipsaci (V) and (N) 62 5.4. Discussion 63 CHAPTER 6. TEMPERATURE EFFECTS 64 6.1. Introduction 64 6.2. Meloidogyne incognita (V)an d (N) 64 6.2.1. Hatching 64 6.2.2, Penetration and development, root galling, reproduction 67 a. Experiments ingreenhous e compartments 67 b. Experiments in Wisconsin tanks 71 c. Experiments inclimati c cells 75 6.2.3. Morphology 79 6.2.4. Discussion 80 6.3. Meloidogynehapla (V )an d (N) 81 6.3.1. Hatching 82 6.3.2. Penetration and development, root galling,reproductio n 83 a. Experimentsi ngreenhous ecompartment s 83 b. Experimentsi nWisconsi n tanks 84 c. Experimentsi nclimati ccell s 90 6.3.3. Survivala t lowtemperatur e 93 6.3.4. Morphology 96 6.3.5. Discussion 97 6.4. Aphelenchusavenae (V )an d (N) 98 6.4.1. Reproduction 98 a. Inoculation experiments 98 b. Singlefemal eculture s 100 c. Minimumtemperatur e 100 6.4.2. Adaptation tolo wtemperatur e 101 6.4.3. Sexrati o 102 6.4.4. Influence ofcontaminatin g fungi 104 6.4.5. Morphology 105 6.4.6. Discussion 109 6.5. Ditylenchusdipsaci (V ) and (N) Ill 6.5.1. Reproduction ofth e(V )garli can dth e(N )onio npopulation s inonio nbulb s . Ill 6.5.2. Reproduction ofth e(V )garli can d the(N )onio npopulation s inphlo xplant s . 113 6.5.3. Reproduction ofth e(N )tuli pan dnarcissu spopulation si nonio nbulb s . 115 6.5.4. Reproduction ofth e(N )tuli p populationi nphlo xplant s 116 6.5.5. Motilityo f the(N )tuli pan d narcissuspopulation s after heat treatments . .119 6.5.6. Reproduction ofth e(N )tuli pan dnarcissu spopulation safte r heattreatment s . 121 6.5.7. Conditioning ofth e(N )tuli ppopulatio n 122 6.5.8. Morphology 123 6.5.9. Discussion 125 6.6. Helicotylenchusdihystera (V ) 127 6.6.1. Reproduction ingreenhous eexperimen t 127 6.6.2. Reproduction inWisconsi ntan kexperimen t 128 6.6.3. Discussion 129 6.7. Pratylenchuscrenatus, and associates (N) 130 6.7.1. Reproductioni ngreenhous eexperimen t 131 6.7.2. Reproduction inWisconsi ntan kexperimen t 132 6.7.3. Discussion 132 6.8. Natural nematodecommunit yi nsoi l(N ) 132 6.8.1. Survivali nsoi l 132 6.8.2. Discussion 133 SUMMARY AND CONCLUSION 136 RESUMEN Y CONCLUSION 145 SAMENVATTING EN CONCLUSIE 155 ACKNOWLEDGEMENTS 163 REFERENCES 164 CHAPTER 1 GENERAL INTRODUCTION AND LITERATURE REVIEW 1.1. GENERAL INTRODUCTION Nematodes are among the most abundant and widespread ofal l organisms (COBB 1915). They are numerous in nearly every moist habitat in which organic material ispresent , such as soil, fresh and salt water, plants, animals and a wide variety of organic substrates. Zoological analyses indicate that nematodes, being the most ubiquitous group of the animal kingdom, constitute more than 80% of all multicellular animals (STÖCKLI 1946). This is mainly due to their great density in soil. The dominant soil animals, apart from Protozoa, are either nematodes, the most numerous in terms of individuals, or arthropods, the most numerous in terms of species (GHILAROV 1967). In order to give an impression of the numbers of animals of different groups that may bepresen t in the soil,th e results of some of the most thorough analy­ ses of soil microfauna are summarized in table 1.I t should be noted, that samp­ ling and extraction techniques are diverse and that their efficiency differs for the various animal groups and for individual workers on a particular group. This is borne out by the reports of two colloquia on such techniques organized at Rothamsted in 1958b y the SoilZoolog y Committee ofth e International Society of Soil Science (MURPHY 1962),an d at Parisi n 1967b yth e Unesco International Biological Program (PHILLIPSON, in print). It is however not likely that other animal groups are lost to a much larger extent than nematodes, so that there is no reason to doubt the numerical dominance of the nematodes as illustrated in table 1. TABLE 1. Number ofnematode san d other numerous multicellular animals inmillion s beneath onesquar emete r ofsoi lcalculate d from thedat apublishe d bydifferen t authors ^. Records After After STÖCKLI GiSIN (1946), modified After FRANZ (1950) (1947) by MACFADYEN Meadow Meadow Arable Arable Meadow (1957) peat sand peat sand Animal groups ^ soil Meadow soil Nematoda 6 1.8 -120 18.2 5.8 4.7 4.5 Acari 0.4 0.02 - 0.12 0.024 0.015 0.009 0.014 Collembola 0.2 0.01 - 0.04 0.013 0.007 0.018 0.025 Other Arthropoda 0.02 0.003 0.002 0.001 0.003 Rotatoria and Tardigrada 0.1 0.27 0 0 0 Enchytrareidae 0.01 0.002 - 0.02 0.003 0.028 0.003 0.033 Lumbricidae 0.0004 0.00003- 0.002 0.00007 0.00035 0 0.00014 Meded.Landbouwhogeschool Wageningen 70-2 (1970) Early records of nematode densities in the soil are often lower. Summaries are made by HYMAN (1951), FILIPJEV & STEKHOVEN (1941), PETERS (1955), STÖCKLI (1943) and OOSTENBRINK (1956). The last mentioned two authors indi­ cate, that the nematode densities found by different authors increased more than thousand fold in the course of some decades owing to the use of improved techniques and that the actual numbers are as a rule several millions per square metre of soil. The experimental part of this study is restricted to soil inhabiting nematodes and to plant parasites, which all have a soil phase as well, with emphasis on the nematofaunas in Venezuela and in the Netherlands. OOSTENBRINK (1966) re­ corded average nematode densities per 100 ml of soil of 3004 and 5620 in arable land and meadows in the Netherlands, and of 794 in various arable grass­ land and bush plots in Venezuela; on an average 30%, 41% and 67% of these nematode communities respectively were known and suspected plant parasites. Nematodes are widely spread as a group. They are known to occur in nearly every soil, but pertinent knowledge about the geographic distribution of indivi­ dual species is scarce. This is due to incomplete coverage of areas and of the habitats within a given area, and to erratic collection and poor identification of the nematodes. Most of the earth's surface has never been included in regional inventories despite the fact that numerous incidental surveys have been made for over a century. These inventories were normally local, they included only a small fraction of the possible nematode habitats of the area and only a part of the fauna at each sampling site wasnormall y caught. Up to some years ago inventories were also very erratic and selective due to lack of quantitative methods for the extraction of collected samples. Recent surveys with socalle d quantitative extraction techniques, however, also overlook the larger part of the species established in a field, unless many large samples are taken and several thousands of nematodes are identified. Usually 10 to 20 species occurring in high densities are recorded from one sample after identifi­ cation of a few hundred specimens, which means that species occurring irregu­ larly distributed or at densities below 1pe r 10 ml of soil often go undetected. Scrutiny of one old meadow in Belgium by taking eight samples at different places and times and identification of about 5000 specimens revealed the pre­ sence, however, of at least 69 species, which was then the greatest number of species recorded from onesingl e field (COOMANS 1962). Other habitats may even be richer in species: Filipjev found up to 140 species of nematodes in a single sample of sea sand at the Murman coast (FILIPJEV & STEKHOVEN 1941). Identification of the nematodes raises special problems (STEINER 1956, ALLEN 1960, LOOF 1960, DE CONINCK 1968).