The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries.

M-14
ISBN 92-5-103827-9

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying or otherwise, without the prior permission of the copyright owner. Applications for such permission, with a statement of the purpose and extent of the reproduction, should be addressed to the Director, Publications Division, Food and Agriculture Organization of the United Nations, Viale delle Terme di Caracalla, 00100 Rome, Italy.

© FAO 1995

Contents

Preface
Abbreviations
Introduction
Part I

Chapter 1: The nature of virus and virus-like disease agents of citrus

Viruses, viroids and phloem-restricted prokaryotes
Graft-transmissible diseases of unknown aetiology
Bibliography

Chapter 2: Interactions between virus and virus-like pathogens and the host plant: susceptible, tolerant and resistant citrus species

Bibliography

Chapter 3: Transmission and spread of virus and virus-like citrus pathogens

Polyembryony of citrus seeds
Bud propagation
Mechanical transmission
Insect and mite transmission
Other means of transmission
Bibliography

Chapter 4: Techniques for the detection and identification of virus and virus-like citrus pathogens

Visual inspection and its limitations
Indicator plants: Biological indexing
Laboratory indexing
Bibliography

Chapter 5: Production of citrus clones free of virus and virus-like pathogens

Visual inspection and indexing
Production of nucellar clones
Shoot-tip grafting
Bibliography

Chapter 6: Short description of major citrus diseases in the near east

Viroid and viroid-like diseases
Virus and virus-like diseases
Diseases involving phloem restricted prokaryotic agents
Fungal diseases
Bacterial diseases: Citrus canker
Bibliography

Chapter 7: Citrus stubborn disease in the Syrian Arab Republic and natural transmission of its causal agent, Spiroplasma citri

Natural spread of S. citri in the Tadla region of Morocco
Stubborn in the Syrian Arab republic
Natural transmission of S. Citri in the Syrian Arab republic
Conclusion
Bibliography

Part II

Chapter 8: Algeria

Citriculture in Algeria
Virus and virus-like diseases
Other disease problems
Recommendations
Bibliography

Chapter 9: Cyprus

Citrus growing
Incidence of virus and virus-like diseases in citrus orchards
Bibliography

Chapter 10: Egypt

Virus and virus-like diseases
Other observations
Integrated protection programme for citrus improvement
Recommendations
Bibliography

Chapter 11: The Islamic Republic of Iran

Introduction of new citrus species and varieties
Incidence of virus and virus-like diseases
Other virus and virus-like diseases
Virus and virus-like diseases: General conclusions
Other important, non-viral diseases
The threat of witches' broom disease of Lime
Bibliography

Chapter 12: Iraq

Virus and virus-like diseases in Iraq
Obsolete horticultural practices and phytophthora gummosis
Stubborn
Diseases of unknown cause
Genetic problems
Conclusions
Bibliography

Chapter 13: Jordan

Virus and virus-like diseases in Jordan
Recommendations
Bibliography

Chapter 14: The Libyan Arab Jamahiriya

Citrus growing in the Libyan Arab Jamahiriya
Virus and virus-like diseases
Other observations
Bibliography

Chapter 15: Morocco

Citrus growing in Morocco
Virus and virus-like diseases
Control of virus and virus-like diseases
Other observations
Recommendations
Bibliography

Chapter 16: Oman

Witches' broom disease of lime nomenclature
S. citri in ornamental periwinkle in Nizwa
Virus and virus-like diseases
Defoliation and dieback of lemon and sweet lime trees at Nizwa
Horticultural practices and phytophthora Gummosis
Miscellaneous disorders, injuries and inadvisable practices
Citrus canker
Conclusions and summary
Bibliography

Chapter 17: Pakistan

Citrus in Pakistan
Background information on citrus diseases in Pakistan
Citrus diseases in India
Decline of citrus trees in Pakistan
Tristeza
Exocortis
Gummy bark of sweet orange and cachexia of Mandarin
Bud-union crease of sweet orange trees on rough lemon rootstock
Leaf yellow vein clearing - An unidentified disorder of lemon trees
Sour orange bark pegging and gumming
Witches' brooms of calamondin trees
Citrus canker
Horticultural practices
Conclusions
Bibliography

Chapter 18: Saudi Arabia

Greening disease and its psyllid vectors
Other virus and virus-like diseases
Phytophthora gummosis - a fungal disease
Bacterial disease: Citrus canker
Bibliography

Chapter 19: Somalia

Mogadishu region: Citrus cultivars and climatic data
Fungal diseases of citrus in the Mogadishu region
Virus and virus-like diseases in the Mogadishu region
Exocortis
Important diseases probably not present in the Mogadishu region
Diseases of citrus in the Mogadishu region: A summary
Hargeisa region: General information and climatic data
Greening
Tristeza in the Hargeisa region
Other virus and virus-like diseases
Fungal diseases
Salt toxicity
Insect pests
Conclusions and recommendations
Bibliography

Chapter 20: The Sudan

Major varieties and rootstocks
Infectious diseases
Non-infectious disorders
Greening
Tristeza
Conclusions and recommendations
Bibliography

Chapter 21: The Syrian Arab Republic

Virus and virus-like diseases
Conclusion
Bibliography

Chapter 22: Tunisia

Citrus growing in Tunisia
Virus and virus-like diseases
Other observations
Recommendations
Bibliography

Chapter 23: Turkey

Citrus growing in Turkey
Virus and virus-like diseases
Other disease problems
Visits to agricultural agencies
Recommendations
Bibliography

Chapter 24: The United Arab Emirates

Witches' broom disease of Lime
Virus and virus-like diseases
Citrus canker
Miscellaneous problems
Conclusions
Bibliography

Chapter 25: Yemen

Northern Yemen
Southern Yemen
Bibliography

Conclusion
Annex table
Figures

Figures 1 - 162
Figures 162 - 322