TAXONOMY AND CULTIVAR DEVELOPMENT OF POA PRATENSIS L. David P. Byres 1 13 BOTANY ORARY PhD. University of Edinburgh 1984 1) Declaration. This thesis was composed by myself, and the work described herein is my own. David P. Byres CONTENTS Acknowledgements . • I \/ Abstract . Section A . Taxonomy. Chapter 1. Introduction. 1.1 Introduction ..........................................1 1.2 Taxonomy .............................................1 1.3 Cultivar Development ............................... 4 Chapter 2. Literature Review : Taxonomy 2.1 Introduction ............. .............................7 2.2 History of the Taxonomic Treatment of of Poa pratensis L. s.1............ ....... 10 2.3 Taxonomic Characters used by previous workers .........14 Chapter 3. Materials and Methods. 3.1 Environmental Variation .................... 20 3.2 Population and Herbarium Studies .......... ............26 3.3 Taxonomic Analysis of Biotypes and Cultivars... ... ... 36 3.4 Statistical Analysis ..................................37 Chapter 4. Effect of Environmental Variation on Morphology. 4.1 Introduction .......................................... 38 4.2 Results ........................................ .......38 Chapter 5. Study of Poa pratensis Populations. 5.1 Introduction .......................................... 49 5.2 Results ........................ 49 Chapter 6. Study of Herbarium Material. 6.1 Introduction ......................................... 60 6.2 Results ....................... 60 Chapter 7. Morphological Examination of Biotypes and Cultivars. 7.1 Introduction ......................................... 83 7.2 Results .............................................. 83 Chapter 8. Discussion of Section A. 8.1 Discussion ........................................... 89 Section B. Cultivar Development. Chapter 9. Literature review : Cultivar Development. 9.1 Characters required in Poa pratensis cultivars ....... 95 9.2 Germination ......................... ......... 98 9.3 Cultivar development in Poa pratensis ....... ......... 99 Chapter 10. Materials and Methods. 10.1 Collection of plant material ................... 101 10.2 Experimental sites .................. 106 10.3 Plant survival ........................... 1 2 0 10.4 Dry matter production ................................ 120 10.5 Ground cover ......................................... 123 10.6 Disease .............................................. 124 10.7 Colour ................. 126 10.8 Flowering ..................... 127 10.9 Meteorological conditions ........................... .128 10.10 Dalmally ............................................. 143 10.11 Seed production ...................................... 145 Chapter 11. Results from Experimental Plots. 11.1 Introduction ............................ 147 11.2 Results ...................................... 147 11.3 Plant Survival ....................................... 149 11.4 Dry Matter Production . .155 11.5 Ground Cover ........................................167 11.6 Disease .............................................178 11.6.1 Mildew Infection ............................178 11.6.2 Rust Infection .................................183 11.6.3 Drechslerapoae Infection ......................191 11.7 Colour .............................................. 1 9 6 11.8 Flowering ..........................................• 205 Chapter 12. Seed production and Germination. 12.1 Seed production .....................................208 12.2 Results .............................................208 12.3 Germination tests ...................................211 12.4 Results ......................• ...........• ..... 212 Chapter 13. Discussion of Section B. 13.1 Discussion ......• ...................................218 Chapter 14, General Discussion and Conclusions. 14.1 Discussion ..........................• ...............230 14.2 Conclusions .............................. 2 42 14.3 Future Work ..........................................244 Bibliography . ....................• .............................247 Acknowledgements I am very grateful to my supervisors, Dr P.M.Smith at the Botany Department, Edinburgh University, and Mr G.Wallace and Dr R.N.Eckersall at Scottish Agricultural Industries Plc., for their advice, assistance and encouragement during the course of this study. I would also like to thank Dr J.H.Lennard for advice on the identification of fungal pathogens, and Dr M.Talbot for the use of his 'Duncan's Multiple Range Test' computer program. I am greatly indepted to the following, who provided me with land for experimental sites Mr J.Reid, of Baibridie, Crathes, Mr I.Blackhall of Milton, Kirktown of Durris, Mr J.McLaren of Craigs Farm, Dalmally, Dr F.Harper of the Edinburgh School of Agriculture, and Dr R.Armstrong of the Hill Farming Research Organisation, Sourhope. The work described in this thesis was carried out while I was In receipt of an S.E.R.C. Case award, for which I am very grateful. V ABSTRACT Poa pratensis L. s.l. (Gramineae) is a common wild plant in Britain, but despite its economic importance - primarily as an amenity grass - the taxonomy and cultivar development of this species has been relatively neglected in this country. The two main aims of this work were to investigate the taxonomy of Poa pratensis, in Britain primarily, and to assess the potential for producing cultivars with improved performance, using the indigenous biotypes from Scotland. The morphology of plants from three separate populations in Scotland was examined, as well as herbarium specimens from the whole of Britain, and the other main areas of distribution of Poa pratensis s.l.. Great morphological variability was evident, both within populations and over a wide geographical range, and this transcended the boundaries of the putative intra-specific taxa: subsp angustifolia, subsp pratensis and subsp subcaerulea. Many plants were found which had a mixture of morphological characters normally attributed to two or more subspecies. From these results, and also the geographical overlap of the supposed subspecies in Britain, it was concluded that the use of specific or subspecific rank was inappropriate for the taxa subcaerulea and angustifolia, and that these should be considered to be part of the spectrum of variation within the single species Poa pratensis L. Insufficient material of subsp alpigena, which does not grow in Britain, was examined to allow any conclusions to be drawn about the validity of the subspecific rank attributed to this taxon. Twenty three biotypes of Poa pratensis were collected from around Scotland, and these were grown in three main experimental sites - near Aberdeen, at Edinburgh, and in the Cheviots. Four cultivars were used as controls. Approximately twenty visits were made to each site over two years, and on each occasion the plants were cut to a height of 2.5cm. The characters recorded at the experimental sites were : plant survival, dry matter production, ground cover, disease resistance and plant colour. The wild biotypes showed considerable physiological diversity, and the cultivars were outperformed, in all the characters examined, and at almost every site, by one or more biotypes. Four of the biotypes showed considerable potential as possible future cultivars. No correlation was apparent between the taxonomic position of plants within Poa pratensis and their performance in experimental plots. The initial tillering rate of the plants was the best character found for predicting their future performance. SECTION A. CHAPTER 1. INTRODUCTION 1.1 Introduction The subject of this study is Poa pratensis L. s.l., which is one of over four hundred species in the genus Poa. Although it is a grass of economic importance, the taxonomy of this species has been relatively neglected, particularly in Britain. One of the aims of the present work was to examine Scottish plants and also herbarium specimens of Poa pratensis s.l. from other parts of the world in order to investigate the taxonomy of this species. Cultivated varieties ( 'cultivars' ) of Poa pratensis are used in Britain primarily for amenity grass for lawns, sports turf and roadside verges. Poa pratensis is a common plant growing wild throughout Britain, but at present all the cultivars used in Britain are imported from abroad. There has been little work done on improvement of Poa pratensis cultivars, and no cultivars are available that originate in Britain. This species has therefore been neglected in terms of cultivar development in Britain. The second aim of this thesis was to compare the performance in experimental plots of indigenous Scottish Poa pratensis with some of the imported cultivars, to find out whether cultivars with improved performance could be produced from wild plants. These two aspects of the work are discussed below. 1.2 Taxonomy The genus Poa is in the Pooideae (Gramineae), a subfamily 1 of mainly north temperate distribution [1]. Temperature is probably the main limiting factor in the distribution of Poa itself [2]: generally, Poa is more tolerant of cold than of heat, and so in the tropics it is found only at high altitude [3], however it flourishes in temperate areas. Poa pratensis is distributed as a wild plant throughout Europe, especially in the north, also North Africa, temperate Asia and North America [4]. It is a species with wide morphological variation [5], and there is debate as to the number and taxonomic position of inter-specific groups. Previous workers have divided Poa pratensis s.l. into between 4 and 22 entitles