Circumscription of Murraya and Merrillia (Sapindales: Rutaceae: Aurantioideae) and Susceptibility of Species and Forms to Huanglongbing
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CIRCUMSCRIPTION OF MURRAYA AND MERRILLIA (SAPINDALES: RUTACEAE: AURANTIOIDEAE) AND SUSCEPTIBILITY OF SPECIES AND FORMS TO HUANGLONGBING Student: Nguyen Huy Chung Principal Supervisor: Professor G Andrew C Beattie, University of Western Sydney Co-supervisors: Associate Professor Paul Holford, University of Western Sydney Dr Anthony M Haigh, University of Western Sydney Professor David J Mabberley, Royal Botanic Garden, Kew Dr Peter H Weston, National Herbarium of New South Wales Date of submission: 31 August 2011 Declaration The work reported in this thesis is the result of my own experiments and has not been submitted in any form for another degree or diploma at any university or institute of tertiary education. Nguyen Huy Chung 31 August 2011 i Acknowledgements I would first and foremost like to thank my supervisors, Professor Andrew Beattie, Associate Professor Paul Holford, Dr Tony Haigh, Professor David Mabberley and Dr Peter Weston for their generous guidance, academic and financial support. My research required collection of pressed specimens and DNA of Murraya from within Australia and overseas. I could not have done this without generous assistance from many people. I am thankful to Associate Professor Paul Holford and Ms Inggit Puji Astuti (Bogor Botanic Garden, Indonesia) who accompanied me during the collection of samples in Indonesia; to Mr Nguyen Huy Quang (Cuc Phuong National Park) and Mr Nguyen Thanh Binh (Southern Fruit Research Institute), who travelled with me during collecting trips in the southern Việt Nam and to Cuc Phuong National Park in northern Việt Nam; to Dr Paul Forster (Brisbane Botanic Garden) who accompanied me during the collection of samples in Brisbane; and to Mr Simon Goodwin who accompanied me during the collection samples in the Royal Botanic Garden, Sydney; to Dr Cen Yijing (South China Agricultural University) who travelled with Prof Beattie to collect specimens from Yingde, in Guangdong. The following people provided Murraya specimens or DNA extracts of Murraya accessions: Dr Trinh Xuan Hoat, Plant Protection Research Institute (PPRI), Hanoi, Việt Nam; Ms Inggit Puji Astuti, Center for Plant Conservation, Bogor Botanic Garden, Indonesia; Dr Siti Subandiyah, Faculty of Agriculture, Gadjah Mada University, Indonesia; Dr Shahid Nadeem Chohan, Department of Biosciences, COMSATS Institute of Information Technology, Islamabad, Pakistan; Dr Cen Yijing and Dr Deng Xiaoling and their students at South China Agricultural University; Prof Zhang Dianxiang, South China Botanical Garden; ii Dr Hung Shih-Cheng, Plant Protection Department, Chiayi Agricultural Experiment Branch, Agricultural Research Institute, Council of Agriculture, Executive Yuan, Taiwan; Dr Chandrika Ramadugu, University of California, Riverside, United States of America; Dr Susan Halbert, Division of Plant Industry Entomology, Florida Department of Agriculture and Consumer Services, United States of America; Dr Silvio Lopes, Fundo de Defesa da Citricultura, São Paulo, Brazil; Mr Fanie Venter, Botanical & Environmental Consultant, Queensland, Australia; Mr Graham Schultz, Biosecurity and Product Integrity, Department of Regional Development, Primary Industry, Fisheries and Resources, Darwin, Australia. I express my sincere thanks to all of them for their kind support. I thank Dr Mark Williams, School of Natural Sciences, University of Western Sydney, for his guidance and support in gas chromatography (GC) analysis. I also would like to thank Elizabeth Kabanoff, Linda Westmoreland, and Gillian Wilkins, Centre for Plant and the Environment for their useful assistance. Elizabeth Kabanoff took the scanning electron micrographs in Chapter 4. I am very grateful to the Australian Centre for International Agricultural Research (ACIAR) for offering me a ‘John Allwright Fellowship’, the Centre for Plants and the Environment, University of Western Sydney for use of its research facilities, and to Plant Protection Research Institute, Việt Nam, for supporting me to undertake the study overseas. iii Summary As circumscribed by Swingle & Reece (1967), Murraya paniculata (L.) Jack [Rutaceae: Aurantioideae: Aurantieae] comprises Murraya paniculata var. paniculata (L.) Jack and three varieties, Murraya paniculata var. omphalocarpa (Hay.) Tan., Murraya paniculata var. ovatifoliolata (Engl.) Domin, and Murraya paniculata var. zollingeri Tan. The widely cultivated ornamental known variously as orange jasmine, orange jessamine or mock orange is often called Murraya exotica L. This latter epithet was regarded by Swingle & Reece (1967) as a junior synonym of Murraya paniculata and opinions of botanists on this issue have been divided for more than 200 years. My interest in the status of the ornamental form stemmed from the need for its status and origins to be resolved, as it is a transient host of a devastating disease of citrus known as huanglongbing. This disease is caused by phloem-limited putative species of bacteria ‘Candidatus Liberibacter spp.’ [α-Proteobacteria]. The vector of the disease, which throughout most of Asia and the Americas is caused by ‘Candidatus Liberibacter asiaticus’, is the Asiatic citrus psyllid (Diaphorina citri Kuwayama [Hemiptera: Psyllidae]), a species that is native to India and that may have evolved with a species of Murraya (sensu lato). Orange jasmine is the favoured host of the psyllid. My project focused on the taxonomic status of Murraya exotica as a species but also included the relationship between Murraya and Merrillia caloxylon. My research was based on the molecular biology, morphology and phytochemistry of accessions collected from Asia, Australasia and the Americas. I also tested these accessions for the presence of the HLB pathogens. Six regions of the maternally-inherited chloroplast genome (trnT-rps4, trnCGCA-ycf6, trnL-F, rps16, matK-5′trnK, psbM-trnDGUC) were amplified by PCR and sequenced. In addition, part of the internal transcribed spacer (ITS) region of the nuclear-encoded ribosomal RNA operon was also sequenced. The data obtained were subjected to phylogenic analysis using parsimony and Bayesian inference. The phylogenetic results derived from the chloroplast genome, as well as the nuclear ITS region, indicated that Murraya exotica is a species. This was supported by: a phylogenetic tree based on characters of basal and terminal leaflets; principal component and redundancy analysis of elliptic Fourier descriptors based on the iv shape of basal and terminal leaflets and a separate analysis of the dimensions of basal and terminal of leaflets, and the basal angles the leaflets; discriminant function analysis of quantitative characters of basal and terminal leaflets; and phytochemistry of leaflet and bark ethanol and n-hexane extracts. The molecular and morphological studies also indicated that, in addition to Murraya exotica, other taxa formerly classified as Murraya paniculata comprise: Murraya paniculata (L.) Jack from Indonesia (syn. Camunium vulgare Rumph. and Murraya sumatrana Roxb.); Murraya asiatica n. sp. ineditus from mainland Asia; and Murraya ovatifoliolata (Engl.) Domin., comprising small and large leaflet forms of Murraya ovatifoliolata var. ovatifoliolata (Engl.) Domin. n. comb ineditus, and Murraya ovatifoliolata var. zollingeri (Tan.) n. comb. ineditus and two hybrids: Murraya × omphalocarpa Hay. ineditus, small and large leaflet forms, possibly with Murraya exotica as the male parent and a form of Murraya ovatifoliolata as the female parent; and Murraya × cycloopensis ineditus from Papua, possibly with Murraya exotica as the female parent and a form of Murraya ovatifoliolata as the male parent. I developed a key to the taxa based on leaf and leaflet characters. I found no evidence to reunite Merrillia caloxylon with the genus Murraya. I only detected ‘Candidatus Liberibacter asiaticus’ in Murraya exotica accessions from Brazil and China. v Table of Contents Acknowledgements ........................................................................................................... ii Summary .......................................................................................................................... iv Chapter 1: Introduction ..................................................................................................... 1 1.1. Aims, Hypotheses and Objectives .................................................................... 6 Chapter 2: Literature Review ............................................................................................ 7 2.1. The Aurantioideae sensu Swingle (Swingle & Reece 1967) ............................ 7 2.2. The tribe Citreae (Aurantieae) sensu Swingle (Swingle & Reece 1967) ......... 8 2.3. The Tribe Clauseneae sensu Swingle (Swingle & Reece 1967) ...................... 8 2.4. Current circumscription of the genus Murraya König ex L. ............................ 9 2.5. Murraya exotica L. and Murraya paniculata (L.) Jack: one species or two? 11 2.6. Rumphius’s notes and descriptions of Camunium vulgare and Camunium japonense ........................................................................................................ 19 2.7. Descriptions of Murraya paniculata and Murraya exotica ............................ 22 2.8. The genus Merrillia Swingle .......................................................................... 28 2.9. Huanglongbing (HLB) .................................................................................... 30 2.10. Molecular markers in HLB research .............................................................