Cytology, Ploidy and Molecular Taxonomy of Prosopis Juliflora DC and Prosopis Pallida HBK
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Cytology, Ploidy and Molecular Taxonomy of Prosopis Juliflora DC and Prosopis Pallida HBK Sherry, Minu Unpublished PhD thesis deposited in CURVE February 2015 Original citation: Minu, S. (2012) Cytology, Ploidy and Molecular Taxonomy of Prosopis Juliflora DC and Prosopis Pallida HBK. Unpublished PhD thesis. Coventry: Coventry University Some images and a research paper have been removed due to third party copyright. The unabridged version of the thesis can be viewed at the Lanchester Library, Coventry University Copyright © and Moral Rights are retained by the author(s) and/ or other copyright owners. This version may differ to the published paper. A copy can be downloaded for personal non-commercial research or study, without prior permission or charge. This item cannot be reproduced or quoted extensively from without first obtaining permission in writing from the copyright holder(s). The content must not be changed in any way or sold commercially in any format or medium without the formal permission of the copyright holders. CURVE is the Institutional Repository for Coventry University http://curve.coventry.ac.uk/open ABSTRACT Prosopis juliflora (Sw.) DC. and P. pallida (H.&.B. ex Willd.) H.B.K. occur naturally in the Americas and they are morphologically similar species. They are multipurpose trees and their ability to grow in poor soil conditions has encouraged their introduction throughout the arid regions of the tropics and semi tropics. The taxonomy of the genus Prosopis Linnaeus emend. Burkart is unclear and a revision of the genus is suggested by several studies. Due to their similarity, the differentiation of P. juliflora and P. pallida is difficult. Although there has been some success in differentiating the species using ploidy, leaf morphology and molecular markers, further approaches are required. This study looked for suitable cytological characters and molecular markers that would differentiate the two tropical species. The cytological character analysis allowed for the development of a dichotomous key for their identification based on leaf stomatal characters. Stomatal length and epidermal cell density are the two characters on which the keys were developed. Correct identification of the species will allow for genetic improvement programmes and conservation efforts in the native regions. Multivariate statistical analysis showed that P. juliflora and P. pallida were separable into two groups. This could help in the classification of unknown herbarium specimens or previously misidentified samples. The phylogenetic relationship of the two species is also disputed and previous RAPD studies show close genetic similarity between the two species, suggesting a reconsideration of the series within section Algarobia. There are also disputes regarding the geographical distribution of both species and naming of new species. In this study, similarity index analysis and cluster analysis on the RAPD data revealed P. juliflora to be more closely related to North American Prosopis spp. than to P. pallida. This result does not agree with other published studies which identifies them i Abstract as closely related species, but agrees with the classification of Burkart. In the present study, the transferability of microsatellite markers developed from P. chilensis (Molina) Stuntz emend. Burkart and P. flexuosa DC. to other Prosopis species was studied. The microsatellite markers gave successful amplification profiles in some of the 13 Prosopis species analysed. Chloroplast DNA intron region was also utilised in this study to detect potentially informative sequences which could differentiate the two species. The trnL- trnF intergenic spacer region in the cpDNA was utilised. This approach was able to confirm the sequence difference in the spacer region between the two species and future work involving additional DNA regions in the chloroplast gene would provide more insight into the phylogenetic relationship of all the species. This could also clear the taxonomical confusion surrounding the genus as a whole. This study has improved knowledge on the relationship between the morphologically similar tropical P. juliflora and P. pallida. The differentiation of the two species using cytology and molecular markers has provided an improved understanding of these resourceful species. ii ACKNOWLEDGEMENTS I would like to thank my Director of Studies Dr. Ashok Patel for his guidance, encouragement and excellent advice throughout this study. Sincere thanks to my supervisors Prof. Philip J. Harris and Dr. Steve Smith (Coventry University) for their invaluable experience and advice on Prosopis. I would like to thank Dr. Paul Hand (Warwick HRI, Wellesbourne) for his expertise and advice on Prosopis molecular work; and to Dr. Janey Henderson for her guidance. My sincere thanks to Dr. Anton Rosenfeld (HDRA) for providing seeds of Prosopis species. I also extend my gratitude to all the lab staff, Neil, Sue and Vicky, for their timely help. Lastly, I would like to thank my friends and family for their continuous support, prayers and encouragement. I am greatly indebted to Sherry for his love, encouragement, patience and moral support throughout. iii CONTENTS ABSTRACT .................................................................................................................. I ACKNOWLEDGEMENTS ...................................................................................... III CONTENTS................................................................................................................ IV LIST OF FIGURES ................................................................................................. VII LIST OF TABLES ..................................................................................................... IX 1. INTRODUCTION ................................................................................................ 1 1.1 Introducing the genus Prosopis ..................................................................... 1 1.2 Taxonomy of the genus .................................................................................. 2 1.3 Natural distribution of the genus ................................................................. 8 1.4 Prosopis and its uses ....................................................................................... 9 1.5 Prosopis juliflora and Prosopis pallida ........................................................ 11 1.5.1 Problems in identification of P. juliflora and P. pallida ........................ 12 1.5.2 Proposed taxonomic revisions to P. juliflora and P. pallida .................. 14 1.5.3 Comparative morphology of P. juliflora and P. pallida ......................... 19 1.5.4 Cytotaxonomy and ploidy ...................................................................... 22 1.5.5 Resource value of the two species .......................................................... 23 1.6 Research, scope, aims and objectives ......................................................... 29 2. DIFFERENTIATION OF PROSOPIS JULIFLORA AND PROSOPIS PALLIDA BASED ON STOMATAL CHARACTERS AND THEIR POLYPLOIDISATION BY COLCHICINE .................................................... 31 2.1 Introduction .................................................................................................. 31 2.1.1 Differentiation of P. juliflora and P. pallida using stomatal characters . 31 2.1.2 Polyploidisation of P. juliflora and P. pallida using colchicine .......... 33 2.2 Materials and methods ................................................................................ 36 2.2.1 Stomatal character measurements of P. juliflora and P. pallida ............ 36 2.2.2 Polyploidisation of P. juliflora and P. pallida ........................................ 42 2.3 Results ........................................................................................................... 45 2.3.1 Differentiation of P. juliflora and P. pallida using stomatal characters . 45 2.3.2 Polyploidisation of P. juliflora and P. pallida ........................................ 54 2.4 Discussion and conclusions ......................................................................... 60 2.4.1 Differentiation of P. juliflora and P. pallida on stomatal characters .... 60 iv Contents 2.4.2 Polyploidisation of P. juliflora and P. pallida using colchicine ............ 63 3. MOLECULAR DIFFERENTIATION BETWEEN PROSOPIS JULIFLORA, PROSOPIS PALLIDA AND SELECTED SPECIES OF PROSOPIS ON THE BASIS OF RAPD AND MICROSATELLITE TRANSFERABILITY STUDIES ............................................................................................................. 69 3.1 Introduction .................................................................................................. 69 3.2 Materials and methods ................................................................................ 75 3.2.1 Prosopis accessions ................................................................................ 75 3.2.2 DNA extraction ....................................................................................... 78 3.2.3 Randomly Amplified Polymorphic DNA (RAPD) analysis ................... 79 3.2.4 Microsatellite marker amplification ....................................................... 82 3.3 Results ........................................................................................................... 85 3.3.1 RAPD analysis of Prosopis species ........................................................ 85 3.3.2 Cluster analysis ......................................................................................