fruit production in the sultanate of oman

Sultan Qaboos University College of Agricultural & Marine Sciences

PROCEEDINGS of the workshop

Integrated Approaches to Fruit Production and Postharvest Management in Arid Climates Edited By Rashid A. Al-Yahyai Michael L. Deadman

Fahad A. Al Said Linus U. Opara

PROCEEDINGS of the workshop Integrated Approaches to Fruit Production and Postharvest Management in Arid Climates Jointly Organized By: Sultan Qaboos University, Sultanate of Oman & Stellenbosch University, Republic of South Africa

29-31 MAY 2010 Published By: Sultan Qaboos University, Muscat, Oman Copyright © May 2011 Project: SR/AGR/CROP/08/01

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TABLE OF CONTENTS

TOPIC

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Introduction

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Organizing Committee

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Speaker Profiles

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Full-Length Papers

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Fruit production in the Sultanate of Oman, Al-Yahyai

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Citrus production in arid climates: The South African Experience, Barry, et al. Pre-harvest management of fruit quality with emphasis on efficient nutrient uptake and distribution to the fruit, Lötze & Kotze Effects of rootstocks on postharvest characteristics, mineral contents and granulation of Hamlin orange in Oman, AlHosni, et al.

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Extended Abstracts

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42

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Fruit production and postharvest management in arid climates: Present status and future prospects, Opara Physiological approach to fruit production, Al-Yahyai & Al Said Insect vectors of phytoplasmas: The case of WBDL in Oman, Al-Wahaibi Managing citrus diseases: An integrated approach to research and extension, Fouri

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Citrus tristeza virus and root diseases of citrus in Oman, AlSadi, et al.

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57 60 68

Proceedings of the Workshop: Integrated Approaches to Fruit Production & Postharvest Management in Arid Climates.

29-31 May 2010 Sultan Qaboos University Sultanate of Oman

Physiological responses and postharvest quality of banana as affected by storage conditions, Al-Waili, et al. Healthy fruits of Oman: The pomegranate story, Al-Ani, et al.

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Fruits research in Oman: Accomplishments and perspectives of the Ministry of Agriculture & Fisheries Wealth, Al-Hosni, et al. Mapping and reducing fruit postharvest losses: An integrated approach, Opara Workshop Recommendations

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87

104 107

Workshop Deliberations & Recommendations

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Field visit to al Jabal al Akhdar

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INTRODUCTION

Integrated Approaches to Fruit Production and Postharvest Management in Arid Climates PREAMBLE Fruits are the major agricultural crops of the Sultanate of Oman. The total area currently cultivated is 50% of all crops that also includes vegetables, field and forage crops. Major fruit crops include date palm, banana, mango, lime, coconut and pomegranate. Oman has recently sought to enhance agricultural crop production to meet the increasing demand for food. At the directive of His Majesty the Sultan, the country is planning to increase the cultivated area and enhance agricultural practices, such as through the introduction of modern irrigation systems. However, the country acknowledges the lack of water resources to make it fully self sufficient in agricultural production. Thus, most of the fruit crops consumed in the country are imported from all five continents of the world. South Africa is one of the leading countries exporting fruit crops to Oman and elsewhere. It is the primary exporter of fruits, including temperate, subtropical and tropical fruit crops in the African Continent. South Africa is ranked among the top producers of plums, pears, table grapes and citrus, particularly tangerines and grapefruit, and avocadoes. Additionally, South Africa is a major exporter of apples, peaches, apricots, pineapple, preserved fruits and nuts and fruit juice. Despite the fact that agricultural production contributes to 8% of the country’s total exports, many adverse conditions such as water-shortage and extreme weather conditions as well as pre- and postharvest management problems are common issues facing fruit production in South Africa and Oman.

Recently, the Sultanate of Oman and the Republic of South Africa signed a memorandum establishing a ‘Scientific & Technical Bilateral Cooperation Programme’. The programme aims at fostering scientific collaboration between the two countries and establishes bilateral research projects and academic partnerships. Sultan Qaboos University and Stellenbosch University have taken the lead to make this program a reality with joint student supervision and continued research collaboration and scientific publication co-authorship. This workshop came as another step toward promoting the scientific partnership between two prestigious institutions. Participants presented and discussed topics of great importance to both countries. Topics included food production, preservation and food security, in addition to the new and innovative methods used to enhance productivity and postharvest management of fruit crops, particularly those grown under adverse environmental conditions. ___________________________________ The Organizing Committee

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Oman-South Africa: Scientific & Technical Bilateral Cooperation Programme Oman and South Africa signed a scientific and technological cooperation agreement in Pretoria on 12 March 2007 to enhance scientific and technological collaboration between the two countries. It was signed by HE the Minister of Higher Education on the Omani Side and HE the former Minister of Science and Technology from the South African side. A Joint Committee from the two sides was formed to follow up the implementation of the agreement. I have been privileged to be the representative from the Ministry of Commerce and Industry, Ministry of Agriculture and Fisheries Wealth, Ministry of Higher Education and the Research Council. The highlights of the main activities of the Joint Committee include: The South African side of the Joint Committee visited the Sultanate in Nov. 2008. As a result, six priority areas for cooperation were identified as: renewable energy, water purification and treatment, the petrochemical sector, fisheries and agriculture, information and communication technology and exploitation of minerals. It was agreed to pursue further cooperation in these areas through official visits, workshops, training courses, research collaboration, and short-term consultancies A delegation from SQU and the Ministry of Agriculture and Fisheries Wealth visited South Africa in April 2009. The visit included the Department of Science and Technology, The University of Pretoria, the University of Cape Town, the Center for High Performance Computing, Department of Environmental Affairs and the University of Stellenbosch. During the same period, another delegation from the Research Council visited the Department of Science and Technology and the National Research Foundation.

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A joint call for expression of interest in joint research in the six areas mentioned was circulated to academics and researchers in South African universities in 2009. Twenty respondents have expressed interest to work together with identified Omani colleagues and develop joint research projects. From the Omani side, 14 researchers confirmed their interest to engage in research collaboration with their counterparts from South Africa. I am pleased to see 10 from SQU among which are 6 from the College of Agricultural & Marine Sciences. Research proposals are underway for funding from SQU and the Research Council and possibly the National Research Foundation in South Africa. We are strongly encouraging and supporting the implementation of the scientific and technological agreement between the two countries. I have no doubt that you will extend your full support for this initiative and I hope that our collective efforts will lead to concrete and sustained cooperation. This workshop is a step forward in enhancing this cooperation and a further addition to the successful conferences and workshops organized by the College in its effort to provide continuing education and to disseminate knowledge. I would like to take this opportunity to congratulate the College on its remarkable research achievements which reflect the outstanding performance of its staff and students. In closing, I would like to thank the organizing committee from SQU and the University of Stellenbosch for their hard work and I wish the participants all the best in their technical presentations and discussions during the workshop and a very pleasant stay in the Sultanate. ________________________ Prof. Amer Al-Rawas Deputy Vice-Chancellor for Postgraduate Studies & Research

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Integrated Approaches to Fruit Production and Postharvest Management in Arid Climates Executive Summary Sultan Qaboos University (SQU) hosted a workshop on ‘Integrated approaches to fruit production & postharvest management in arid climates’. The three-day workshop was inaugurated on 29 May 2010 under the auspices of His Excellency Dr. Hilal bin Ali al Hinai, Secretary General of the Scientific Research Council and was held in collaboration with Stellenbosch University, one of the leading research institutes in South Africa. The workshop was organized under the umbrella of the Oman-South Africa Scientific and Technical Bilateral Program and the strategic research project ‘Rejuvenating Lime Production in Oman: Resolving Current Challenges’ funded by a grant provided by His Majesty the Sultan to support research at SQU. The main objective of this workshop was to build scientific collaboration between agricultural research organizations in the Sultanate and their counterparts in South Africa and included a visit by the Vice Rector for Research at Stellenbosch University, Prof. Arnold van Zyl. At the opening ceremony, Prof. Amer Al-Rawas, Deputy Vice Chancellor for Postgraduate Studies & Research & the chair of Oman-South African Joint Committee, highlighted the ongoing scientific and technological collaboration between Sultan Qaboos University and South African research institutions, including Stellenbosch University. This collaboration started in March 2007 with the signing of an agreement between the two countries and continues to grow through exchange of officials and scholars. Dr. Sanmugam Prathapar, the former Dean of the College of Agricultural & Marine Sciences, highlighted the steady research

advancement in the college in partnership with universities and organizations from across the world. During the three days of the workshop, there were thirteen scientific papers presented in four sessions addressing the challenges of fruit production and research in Oman and South Africa, advances in fruit production research, integrated approaches to managing citrus pests, diseases and disorders, and postharvest management and health benefits of fruits. The participants concluded the workshop with the development of a framework for institutional collaboration on research on three fruit crops that are of great importance to Oman and South Africa and which should include pre-harvest management and cultural practices, pest and disease management, postharvest management, and fruit and human health issues of citrus, pomegranate and banana. Participants agreed to initially present a collaborative research proposal investigating priority crops, in particular citrus and pomegranate. On the last day of the workshop, the participants had the opportunity to visit local traditional and modern fruit orchards in al Jabal al Akhdar and the Agricultural Experiment Station at SQU. The workshop was organized in cooperation with the Ministry of Agriculture and Fisheries Wealth and Royal Court Affairs from the Sultanate and Citrus Research International of South Africa.

______________________________________ The Editors

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Rejuvenating Lime Production in Oman: Resolving Current Challenges

Production of lime (Citrus aurantifolia) in Oman has been significantly reduced in recent years. The reduction in yield has been attributed to a combination of abiotic and biotic factors that adversely affected tree growth and productivity. Area cultivated with lime trees is currently 50% of that in 1990, due to Witches’ Broom Disease of Lime (WBDL) associated with Candidatus Phytoplasma aurantifolia. Following its subsequent spread to neighboring countries, such as UAE and Iran, the disease that originated in the Sultanate has the potential to devastate lime production throughout the entire regions of western Asia and North Africa as well as other lime producing areas of the world, thus affecting lime imports to Oman. Moreover, lime production in Oman has been worsened by increasingly stressful abiotic conditions caused by prolonged drought, increasing soil and water salinity and loss of soil fertility. The compounded adverse effects of biotic and abiotic stresses on tree growth and yield have resulted in a loss of tree acreage and profitability and have reduced income from largely traditional farming systems. The unsustainability of tree fruit production has led to the abandonment of many farms, the conversion of fruit farms to forage farms, or to a complete change of land use to other commercial projects. While the causal agent of the WBDL disease has long been identified, many aspects of the disease such as epidemiology, vector studies and sustainable control measures have not been tested. A major research project, aiming at a comprehensive understanding of WBDL in Oman, was started in 2008. The research aims to eventually provide practical solutions for lime growers, enabling them to continue production from diseased trees, while new, long-term solutions through resistant

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cultivars are evaluated and introduced. Several aspects of the current WBDL epidemic have being addressed including DNA fingerprinting of symptomatic and non-symptomatic Omani lime; characterization of the interaction between WBDL and other citrus diseases; and quantification of morphological and biochemical changes in infected trees. Field trials are been established to evaluate hybridized and exotic cultivars of Citrus, particularly lime and studies of vectors and hosts have been initiated. Assessments of methods to optimize fruit production through the management of diseased trees are in progress. _______________________ Project: SR/AGR/CROP/08/01 PI: Rashid Al-Yahyai1 Co-PI: Fahad A. Al Said1 Co-Investigators: A. Al-Sadi1, A. Al-Wahaibi1, I. Khan2, M. Deadman1, S. AlIsmaily3, M. Al-Wardi3, A. Al-Lawati4, A. Al-Matrooshi4, A. Al-Zidjali4.

Department of Crop Sciences, Sultan Qaboos University, Oman Vice Chancellor’s Office, University of Agriculture, Faisalabad, Pakistan 3 Department of Soil, Water & Ag. Eng., Sultan Qaboos University, Oman 4 Directorate General of Agriculture & livestock Research, Ministry of Agriculture and Fisheries Wealth, Oman 1 2

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ORGANIZING COMMITEE

Main Committee:            

Dr Fahad A. Al Said, Convener Dr Rashid Al-Yahyai, Chair, Sultan Qaboos University, Oman Prof. Linus Opara, Co-Chair, Stellenbosch University, South Africa Dr Ahmed Al-Maskri, HoD, Crop Sciences, CAMS, SQU Dr Yahya Al-Hinai, Director of Research, Royal Court Affairs, Oman Eng. Ali Al-Adawi, Ministry of Agriculture and Fisheries Wealth, Oman Mr Masoud Al-Hinai, Director of Administration, CAMS, SQU Mr Yousef Al-Maqbali, Superintendent, Crop Sciences, CAMS, SQU Mrs Latifa Al-Kharusi, Crop Sciences, CAMS, SQU Mr Khamis Al-Habsi, Crop Sciences, CAMS, SQU Ms Zakiya Al-Kalbani, Crop Sciences, CAMS, SQU Representative, Department of Public Relations, SQU

Scientific Committee:         

Dr Rashid Al-Yahyai, Chair, SQU Prof. Linus Opara, Co-Chair, SU Dr Michael Deadman, SQU Dr Majeed Al-Ani, SQU Dr Abdullah Al-Sadi, SQU Dr Ali Al-Wahaibi, SQU Dr Nadiya Al-Saady, SQU Dr Yahya Al-Hinai, Royal Court Affairs, Oman Dr Ali Al-Lawati, Ministry of Agriculture and Fisheries Wealth, Oman

Participating Organizations:     

College of Agricultural & Marine Sciences, Sultan Qaboos University, Oman Ministry of Agriculture and Fisheries Wealth, Oman Royal Court Affairs, Oman Stellenbosch University, South Africa Citrus Research International, South Africa

Logo Design: Mr Ali Al-Raeesi Photo Credits: Dr Rashid Al-Yahyai

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SPEAKER PROFILES

SPEAKER PROFILES

Prof. Karen I. Theron is Full Professor and Chair of the Department of Horticultural Science at Stellenbosch University. She specialises in fruit production and fruit quality. She started her career doing research on cut flowers, mostly indigenous flora of South Africa, but then moved on to fruit research, both on deciduous fruit and citrus and more recently also Mediterranean crops and blue berries. The deciduous fruit research of Prof. Theron focuses on reproductive development, including R-bud initiation and –differentiation, fruit set and thinning, fruit growth and fruit quality. Fruit quality aspects include non-destructive testing and maturity prediction modeling. In citrus, her research revolved around fruit quality e.g. fruit size and fruit internal quality. Prof. Linus Opara is Full Research Professor in the Department of Horticultural Science and holds the South African Research Chair in Postharvest Technology at the University of Stellenbosch. His current research focuses on innovative technologies for cold chain management, quality measurement systems, and mapping postharvest food losses. Prior to his current job, he worked at Sultan Qaboos University in Oman where he developed research programs and courses in postharvest technology and was the Principal Investigator of the Strategic Research Project on “Postharvest technology of fresh Omani produce”, which applied an integrative and multidisciplinary approach linking fruit production, postharvest management, and human health. Dr. Paul Fourie is the Programme Manager for Disease Management of Citrus Research International, the research and technology service provider to the southern African citrus industry. He is seconded to Stellenbosch University as senior researcher in Plant Pathology and his research portfolio focuses on fungicide application technology in citrus orchards

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and packhouses. Prior to his current job, he worked at Stellenbosch University as senior lecturer and researched the aetiology, epidemiology and management of grapevine trunk diseases. Dr. Elmi Lötze is a senior researcher at the Department of Horticultural Science at Stellenbosch University. Initially she was involved in the private sector. She started her research career at the Agricultural Research Council (ARC) investigating climatic factors involved in determining fruit size of apples, and predicting the yield of apple orchards. Her current research focuses on improving quality of deciduous fruit crops. Ongoing projects include the influence of climate and nutrition on pre-harvest and postharvest condition of fruit, postharvest quality problems such as lenticel break down and internal break down of apples. Dr. Majeed Al-Ani is an Associate Professor of Human and Clinical Nutrition and Director of the Dietetic Internship Program at the Department of Food Science and Human Nutrition at Sultan Qaboos University, Sultanate of Oman. He has participated in several research projects and is the Principal Investigator of the project on “Antiatherogenic characteristics of consumption of fruit and vegetables grown in Oman”, focusing on the effects of pomegranate intake on human health. Prior to his current job, he was a Professor at Jordan University of Science and Technology, College of Medicine at the University of Baghdad, and also worked at the University of London. He has developed and taught many courses and supervised many MSc and PhD students in clinical nutrition and biochemistry. Dr. Rashid Al-Yahyai is an Assistant Professor of Horticultural Sciences, specializing in Fruit Production, at the Department of

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SPEAKER PROFILES

Crop Sciences, College of Agricultural & Marine Sciences, SQU. Dr. Al-Yahyai has been investigating the effects of water stress and irrigation deficit on physiological processes, water relations, growth and yield of deciduous and tropical fruit trees. His research interest is to study the effects of biotic and abiotic stress factors on physiology, growth and productivity of horticultural crops with emphasis on heat, drought and salinity effects. Dr. Al-Yahyai is the principle investigator of the Strategic Research Project ‘Rejuvenating lime production in Oman: Resolving current challenges’ that was awarded in 2008. He worked on several other projects including ‘the physiological responses of date palm to water stress’, ‘integrated management of soil and water salinity’, and ‘postharvest technology of fresh Omani produce’, among others. Dr. Ali Al-Wahaibi is an Assistant Professor in the field of Entomology at the Department of Crop Sciences, College of Agricultural & Marine Sciences, SQU. His specialization is biological control of insect pests. He is also interested in the biology and systematics of leafhoppers and planthoppers and their parasitoids. His research focus in the past has been searching/oviposition behavior and other facets of the biology and ecology of egg parasitoids of leafhoppers. He has also been interested since 1997 in the biology, ecology, and management of the dubas bug, a major pest of date palms in Oman. He has been involved in other projects dealing with the management of fruit flies, the insect fauna of mangroves, aphid-plant associations and population dynamics, and vectors of witches’ broom disease of lime. He teaches general entomology, beekeeping, IPM/IDM, and biological control at the undergraduate and postgraduate levels. Dr. Abdullah Al-Sadi is an Assistant Professor of Plant Pathology at the Department of Crop Sciences, College of

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Agricultural & Marine Sciences, SQU. His research focuses on population genetics of fungal and oomycete pathogens and characterization and management of soil-borne pathogens of vegetables, viral, prokaryotic and fungal diseases of citrus and fungal diseases of date palms and native Omani plants. Dr AlSadi is the principle investigator of the strategic project "potential sources of plant pathogenic fungi and bacteria into farms in Oman; 2010-2013" and the project "characterization of gummosis and foot/root rot diseases of citrus in Oman; 2009-2011". He is also a co-investigator in a number of projects including the strategic project on lime. Eng. Abdullah Al-Hosni is a Fruit Production Researcher, formerly at the Ministry of Agriculture and Fisheries Wealth. He worked on several research projects on major fruit crops of Oman including citrus, banana and pomegranates. His main research area was focused on enhancing yield and quality of fruit crops through introduction and evaluation of new cultivars and rootstocks as well as the application of various preharvest treatments. Eng. Al-Hosni has recently completed his Masters of Science at SQU. His thesis topic was “Postharvest Characteristics and Quality Attributes of Selected Exotic Banana Genotypes in Oman”. He is currently working at the Oman Botanic Garden, a national project of the Diwan of Royal Court. Eng. Nafla Al-Waili is a postgraduate student at the Department of Soil, Water & Agricultural Engineering, SQU. She is co-advised by a thesis committee compromised of faculty from Stellenbosch University and SQU. Her M.Sc. thesis topic is “physiological responses and postharvest quality of banana as affected by storage conditions”. Her research interest is the postharvest physiology and technology of crops.

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FULL-LENGTH PAPERS

Fruit production in the Sultanate of Oman, pp 2-15. © 2011 Sultan Qaboos University.

FRUIT PRODUCTION IN THE SULTANATE OF OMAN Rashid Al-Yahyai* Department of Crop Sciences, College of Agricultural & Marine Sciences, Sultan Qaboos University, P.O. Box 34, Al-Khod 123, Oman. The Sultanate of Oman is located in the South-eastern part of the Arabian Peninsula, an area that is considered semi-arid to arid. The average annual rainfall in Oman is approximately 100 mm. However, great variations in geographic and climatic conditions in the country exist which allow for the cultivation of various crops including temperate, subtropical and tropical fruits. The majority of the agricultural production in the Sultanate is located in the coastal regions and interior plains. In these areas, fruit crops dominated by date palm, but also banana, mango, citrus, and other tropical fruit trees are cultivated. In the southern part of the country, the annual monsoon rain falls from May to August. These conditions are suitable for commercial production of several types of tropical fruit crops, primarily coconut and banana, as well as other minor tropical trees such as papaya, Annonas, and sapodilla. In northern Oman, a mountain range, called the Hajar Mountains, peaks at 3,000 m above sea level and receives an average annual precipitation of about 350 mm, the highest in the country. High precipitation coupled with low winter temperatures provide a suitable environment for the cultivation of subtropical and temperate fruit crops. Ancient settlers of these mountains have created terraces where crops such as pomegranate, walnut, apple, pear and stone fruits are grown. Major limitations of fruit production in Oman are biotoc factors including major pests, such as the Dubas bug and Red Palm Weevil of the date palm, and

* Corresponding Author: [email protected]

AL-YAHYAI, R.

FRUIT PRODUCTION IN THE SULTANATE OF OMAN

diseases, such as Which’s Broom Diseases of Lime and Mango Sudden Wilt. Abiotic factors that limit the expansion of fruit crops in Oman are soil and water salinity, poor soil fertility, desertification, and lack of renewable water resources. INTRODUCTION The Sultanate of Oman is located between 26o-16 o N and 51 o-59 o E in the South-Eastern part of the Arabian Peninsula. The total area of Oman is approximately 309,500 km2 with a total coast line of 1700 km bordering the Sea of Oman and the Indian Ocean. Due to the low average annual precipitation (< 100 mm) which is lower than average evapo-transpiration year-round, Oman is referred to as an ‘Arid’ country. Geographically, Oman is predominantly a desert which covers 75% of the total area with little or no vegetation. Nonetheless, the remaining area varies greatly in topographic and climatic characteristics, which allows for the cultivation of various types of fruit crops including tropical, subtropical and temperate fruit crops. Biodiversity of Oman’s fruit crops are influenced by the large variations in topography and climatic conditions. The country’s altitude ranges from sea-level in coastal regions and central Oman to over 2400 m in the mountains located in the northern and southern parts of the country. Climate variations including the amount of rainfall (Fig. 1&2) , relative humidity, and temperature have also been a principle factor that divides Oman into distinct fruit producing agro-climatic zones. OMAN AGRO-CLIMATIC FRUIT PRODUCTION REGIONS Fruit crops are grown throughout the country where water can be supplied. Based on the amount of rainfall, relative humidity, and temperate, Oman agro-climate with regard to fruit production can be grouped into five main categories: 1- The Coastal Plains of Batinah and Sharqiah. The climate is characterized by low rainfall, high relative humidity

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2-

3-

4-

5-


particularly during the summer months, and high temperature during most of the year. This climate allows for the cultivation of mainly subtropical, but to a lesser extent tropical fruit crops. The Interior Region of Buraimi, Dakhlia and Dhahira. Characterized by low relative humidity throughout most of the year. Temperature is cool during winter months that extend from November to February but hot and dry weather prevails during the summer months. Major fruit crops in this region are similar to the coastal plains that include date palm, lime and mango. However, great diversity in cultivars exists among these two distinct regions, for example ‘Um Sella’ is the most cultivated date cultivar in Batinah but ‘Fardh’ and ‘Khalas’ are the most common in the interior of Oman (Dakhlia). The Hajar mountain range that separates the coastal regions from the interior, receives the highest amount of rainfall with an annual average of 350 mm. This mountain chain peaks at approximately 3000 m altitude with subzero temperatures during the winter months. Chill units (i.e. cumulative hours below 7oC) are adequate for the cultivation of various deciduous fruit crops including pome and stone fruits but most significantly pomegranate. The monsoon region of Oman (Dhofar province) is located in most southern part of the country. Unique to this region, the annual monsoon from the Indian Ocean leads to continuous low-intensity rainfall that ranges from 200260 mm annually mainly between May and August. This monsoon climate coupled with moderate temperatures throughout the year allows for the cultivation of tropical and subtropical fruit crops. Coconut, banana, and papaya are the most economical fruit crops in this zone. The central desert region of Oman (Wusta) does not receive adequate rainfall to sustain agricultural

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AL-YAHYAI, R.


production. A scattered oasis system of cultivation, dominated by date palm, characterizes this climatic zone. This region is the least cultivated in the country due to lack of adequate irrigation water and extreme summer heat.

1200.00

Rainfall (mm)

1000.00 800.00 600.00

Average

400.00

Max. Min.

200.00 0.00

Figure 1. Average, maximum, and minimum annual rainfall in various wilayats of Oman (1980-2004).

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50

Rainfall

Temp (Max)


Temp (Min)

300

45 250

35

200

30 25

150

20 100

15 10

Rainfall (mm)

Temperature (oC)

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5 0

0 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 Year

Figure 2. Average annual maximum and minimum temperatures (lines) and rainfall (bars) in the Sultanate of Oman (1980-2004).

MAJOR FRUIT CROPS OF OMAN Fruit production is of significant economic importance in Oman. Fruit crops occupy 58% (42,372 ha) of the total area cultivated in Oman but production constitute a quarter (303,551 MT) of all commodities produced in the country (Fig. 3). Date palm (Phoenix dactylifera) is by far the most important fruit crop in terms of production and value (Table 1) although its cultivation is restricted to the northern part of the country. Banana, on the other hand, is cultivated throughout Oman and is the second most important fruit crop. Banana is another crop that is particularly important for export to countries in the Middle East. Lime and mangoes are major crops grown in various parts of the country.

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AL-YAHYAI, R.


Figure 3. Percentages of fruit crop area and production quantities relative to other agricultural commodities in Oman (MoA, 2005). Table 1. Top commodities produced in Oman [in metric tons (MT)] and their equivalent value in international markets (FAO, 2010). Commodity Dates Tomatoes Bananas Chilies and peppers, green Okra Watermelons Onions, dry Other melons Limes Mangoes Potatoes Sorghum Cabbages and other brassicas Eggplants (aubergines)

Production (Int $1000) 77,574 9,815 4,117 2,535 1,955 1,796 1,672 1,647 1,563 1,551 1,315 1,273 1,089 764

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Production (MT) 255,871 41,426 28,892 7,348 4,736 17,233 9,078 9,289 5,983 6,373 9,067 10,439 7,416 4,753



Area (ha) Others

308.7

Papaya

130.2

Coconut

430.5

Mango

1,508.64

Lime

1,691.34

Banana

2,740.50

Date Palm

35,562.24

Figure 4. Area of major fruit crops grown in Oman in 2008 (FAO,2010). Production (MT) Others

5,745.00

Papaya

2,515.00

Coconut

4,470.00

Mango

Lime Banana

10,910.00 8,385.00 32,915.00

Date Palm

238,611.00

Figure 5. Production of major fruit crops grown in Oman in 2008 (FAO, 2010).

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AL-YAHYAI, R.


Date Palm. The date palm (Phoenix dactylifera) is the predominant fruit crop in Oman and occupies 50% of all crops cultivated and 82% of the total fruit trees in the country (AlYahyai, 2007; Al-Yahyai, 2010). There are currently 7.8 million date palm trees with an estimated production of approximately 239 thousand tons (Fig. 5), which makes Oman one of the top 10 date producing countries in the world. Furthermore, there are large numbers of date palm cultivars in the country that vary among regions in yield and fruit quality. An estimated 180 female and 48 male cultivars are in cultivation in Oman (Al-Yahyai and AlKhanjary, 2008). However, the majority of dates (>75%) are produced from only ten cultivars (Al-Yahyai, 2007; Al-Yahyai, 2010). Numerous challenges are facing date palm cultivation in Oman including biotic factors such as the Dubas Bug (Ommatissus lybicus Bergevin, Hemiptera: Tropiduchidae) and the Red Palm Weevil (Rhynchophorus ferrugineus Olivier, Coleoptera: Curculionidae), two of the most damaging pests of date palm. Moreover, abiotic factors contribute to low yield and fruit quality of dates including adverse climatic conditions such as extreme temperatures, high relative humidity in coastal regions, occurrences of cyclones and severe rain and hail storms, as well as soil and water salinity and traditional outdated methods of cultivation (Al-Yahyai, 2010). Banana. The second largest fruit crop in Oman in area and production is banana (Musa spp.) (Fig. 4 and 5). Banana is cultivated throughout Oman but commercial plantations are concentrated in al-Batinah Region and Dhofar Governorate. There are 2,740 hactares of banana producing approximately 33,000 MT annually (MoA, 2005) from an estimated 30 local and imported cultivars, the most common of which is Dwarf Cavendish (e.g. Malindi and Williams). There is little information on the genetic and phenotypic diversity of banana in Oman and further research

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is needed to address the challenges that face banana production in the country. Mango. Mango (Mangifera indica) is a major fruit crop in Oman with an estimated 390,760 trees grown throughout the Sultanate (MoA, 2005). However, the majority of mangoes (71%) are grown in al-Batinah Region, followed by al-Sharqia and al-Dhahira (about 9% each). Mangoes occupy 1508 hectares that produced 11 MT in 2008 (Fig. 4 and 5). There are numerous seedling cultivars in the country including mono-embryonic and poly-embryonic types. Being mostly cultivated in coastal regions, mango cultivation is threatened by increased salinity levels in these regions. A recent outbreak of mango sudden decline caused by Ceratocystis fungi devastated much of the mangoes in Oman (Al-Adawi et al., 2006; Deadman et al., 2007). Citrus. Due to its geographic location, Oman played a role in the spread of citrus from its origin in Asia to Africa and Europe and subsequently to the New World (Davies and Albrigo, 1994). Among citrus species, Lime (Citrus aurantifolia), locally known as ‘lomi’, is the most traditionally cultivated crop in the country, where it is third in terms of area (1691 ha) after date palm and banana (Fig. 4). More than two decades ago, Oman was famous for its high-quality lime that was exported fresh and dried to many countries around the world. However, since late 1980s with the discovery of Witch’s broom disease of lime caused by a phytoplasma (Garnier et al., 1991), lime production has sharply declined to a quarter of the former yield. Currently lime is imported from the Indian subcontinent to meet local demand. Tahiti lime (C. latifolia) has been introduced to replace the Omani lime but its distribution is limited due to incidence of wood pocket affecting trees older than five years. Other citrus species that have been cultivated in Oman for centuries are safarjal (sweet lime, C. limittoides), balenj (sweet lemon, C. limetta), narenj (sour

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orange, C. aurantium) and atraj, trinj, shamom, or Shkhak (citron, C. medica). Newly introduced oranges (C. sinensis), pomelo (C. grandis), grapefruit (C. paradisi), and mandarins (C. reticulata) have done remarkably well in Oman. However, no data is available about the distribution, area and production of these newly introduced citrus species. Coconut. There are 430 hectares of Coconut (Cocos nucifera) in Oman that produced 4,470 MT in 2008. Coconut is the dominating crop in the southern region where 84% of the 138,803 palms are cultivated (MoA, 2005). The majority of the crop is consumed in local markets, largely by street vendors, for its milk or meat, while a portion of the produce is marketed in northern Oman. Despite the suitable climate for coconut cultivation, lack of processing facilities and markets for this crop is a major limitation to its widespread cultivation in Oman. Pomegranate. The pomegranate (Punica granatum) grows on a commercial scale in the northern mountainous region of Jabal Akhdar of Oman (23o 04' N, 57o 38' E, and approximately 3000 m altitude). Due to its high altitude, the Jabal Akhdar is ideal for the cultivation of pomegranates and other deciduous fruit crops. The minimum temperature during the winter months (December to February) reaches below 0 oC, which allows for the cultivation of various low-chill deciduous fruit crops (Al-Yahyai et al., 2009). This is the single most important crop in this region where a single fruit can be sold at $ 2.56. Several local cultivars of pomegranates are cultivated in Jabal Akhdar, four of which have been studied to determine their fruit development (Al-Yahyai et al., 2009) and postharvest quality (Al-Said et al. 2009). Further research is needed to improve the fruit yield and quality of pomegranates in Oman.

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MINOR TROPICAL FRUIT CROPS Papaya. Papaya (Carica papaya) has been traditionally grown in various parts of Oman. However, papaya cultivation is still limited to household consumption and little large scale cultivation is currently present. In southern Oman, various varieties of papaya have been introduced including ‘Solo’ and ‘Sunrise’ that were found successful with satisfactory yield and fruit quality. Guava. Guava (Psidium guajava) has also been traditionally cultivated for household consumption throughout Oman. However, Guava is highly susceptible to fruit fly and this has limited the commercial production of Guava on a large scale in the country. Annonas. Sugar apple (Annona squamosa) and soursop (A. muricata) have been recently introduced and successfully grown in southern Oman and to a limited extent in al-Batinah region. Annonas can be found scattered in local farms where fruits are consumed fresh, mostly for family consumption. Sapodilla. Sapodilla or Chico sapote (Manilkara zapota) is a commonly grown tree in Oman due to its low pest infestation and disease infection. The fruit is consumed fresh and has been grown on a limited scale in northern and southern Oman. However, due to the low popularity of the fruit for fresh consumption, most trees are grown as windbreaks or on the farm perimeter and fruits are consumed locally. MINOR TEMPERATE FRUIT CROPS Pome fruits such as apple (Malus domestica) and pear (Pyrus communis) have been successfully cultivated in the high-altitude mountains in northern Oman. Similarly, stone fruits including

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peach (Prunus persica), apricot (Prunus armeniaca), and nut crops such as walnut (Juglans regia), almond (Prunus dulcis), and cashew (Anacardium occidentale) are currently cultivated in local small-holder farms in these mountains. Information on these crops remains limited as little research has been done to study cultivation practices and factors that influence yield and fruit quality. WILD FRUITS Several wild plants produce fruits that are traditionally consumed fresh or in various preparations. Monotheca buxifolia (Boot) is a shrub that is commonly found in the northern mountains of Oman, producing small, sweet-tasting fruits (Al-Yahyai and AlNabhani, 2008). Other wild plants that produce edible fruits include nimt (Sageretia spiciflora), utom (wild olive, Olea europaea) , Ziziphus spina-christi (Sidr), and sawqam (Ficus sycomorus). There have been no horticultural studies on these wild plants and information regarding their potential use as cultivated fruit crops in Oman is limited. CONCLUSIONS Fruit crops constitute a major part of agricultural food crops in Oman. Due to its diverse climate and geography, many fruit crops can be successfully cultivated in the Sultanate. However, major challenges and limitations need further research, particularly the limiting biotic and abiotic factors that influence fruit yield and postharvest quality. Preservation of the country’s fruit crop biodiversity is essential as there are numerous date palm, banana, mango and citrus cultivars throughout the country. Economic factors such as labor and market also influence the spread and distribution of fruits. Further research on the limiting factors to fruit production in Oman is essential to ensure the continued availability of locally-produced fruits.

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References Al-Adawi, A., M. Deadman, A. Al-Rawahi, Y. Al-Maqbali, A. AlJahwari, A. Al-Saadi, I. Amri, and M. Wingfield. 2006. Aetiology and causal agents of mango sudden decline disease in the Sultanate of Oman. Eur. J. Plant Path. DOI: 10.1007/s10658-006-9056-x. Al-Said, F., L. Opara, and R. Al-Yahyai. 2009. Physico-chemical and textural quality attributes of pomegranate cultivars (Punica granatum L.) grown in the Sultanate of Oman. J. Food Eng. 90(1): 129-134. Al-Yahyai, R. 2007. Improvement of Date Palm Production in the Sultanate of Oman. Acta Hort. 736:337-343. Al-Yahyai, R. 2010. Current Status of Daye Palm in the Sultanate of Oman. In: H. A. Esechie (ed), Proceedings of the International Conference on Date Palm Production and Processing Technology, Muscat, Oman. pp. 1-6. Al-Yahyai, R., F. Al-Said, and L. Opara. 2009. Fruit growth characteristics of four pomegranate cultivars from northern Oman. Fruits 64(6): 335-341. Al-Yahyai, R. and H. Al-Nabhani. 2008. Botanical description and phenological cycles of Monotheca buxifolia. Acta Hort. 769:247-253. Al-Yahyai, R. and S. Al-Khanjary. 2008. Biodiversity of Date Palm in the Sultanate of Oman. Afr. J. Agr. Res. 3:389-395. Davies, F.S. and L.G. Albrigo. 1994. Citrus. CAB International. Wallingford, UK. Pp. 1-11. Deadman M.L., A. Al Adawi, R. Al Yahyai, and M.J. Wingfield. 2007. Ceratocystis Wilt of Mango in Oman. Proceedings: International Symposium on Prospects of Horticultural Industry in Pakistan, 28-30 March 2007. Institute of Horticultural Sciences, University of Agriculture, Faisalabad, Pakistan. FAO. 2010. Food & Agriculture Organization of the United Nations. http://www.faostat.fao.org). 19 May 2010.

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Garnier, M., L. Zreik, and J. M. Bove. 1991. Witches' broom, a lethal mycoplasmal disease of lime trees in the Sultanate of Oman and the United Arab Emirates. Plant Dis. 75: 546551. MoA. 2005. Agricultural Census 2004/2005. Ministry of Agriculture and Fisheries Wealth, Sultanate of Oman.

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Citrus production in semi-arid climates: the South African experience, pp 16-29. © 2011 Sultan Qaboos University.

CITRUS PRODUCTION IN SEMI-ARID CLIMATES: THE SOUTH AFRICAN EXPERIENCE Graham H. Barry1, Stephan Verreynne2, Etienne Rabe2 and Karen I. Theron2* 1

Citrus Consultant, P.O. Box 5349, Helderberg, 7135, South Africa Department of Horticultural Science, Stellenbosch University, Private Bag X1, 7602 Matieland, South Africa 2

South Africa currently ranks 12th in world citrus production, producing approximately 2.3 million tons of citrus in 2007/08. Yet, South Africa is the second largest exporter of fresh citrus in the world after Spain with 1.3 million tons exported in 2007/08. The latter clearly indicates the importance of the fresh export market as the principal component of the South African citrus industry. Citrus is produced in a wide range of climatic conditions in South Africa, from semi-tropical to semi-desert, resulting in a wide range of citrus cultivars being produced. The semi-desert region is relatively new in terms of citrus production and is characterised by extremes: hot summers and cold winters with the occurrence of frost due to advective conditions. In the cooler, semi-arid Vaalharts area, Navel and Valencia oranges are produced, whereas grapefruit and Valencia oranges are produced in the hotter, semi-arid lower Orange River area. Until the late 1970’s the citrus industry used rough lemon as the principal rootstock, but since the 1980’s the trend has shifted to Carrizo and Troyer citrange and Swingle citrumelo. This aspect is important for the competitiveness of the South African citrus industry to produce high quality fruit and compete with Argentina, Uruguay and Australia where trifoliate rootstock is preferred due to the cold tolerance it imparts on the scion. Nursery trees are commonly headed at 60 to 70 cm height to

* Corresponding Author: [email protected]

BARRY, ET AL.

CITRUS PRODUCTION IN SEMI-ARID CLIMATES

allow scaffold development at a height of 40 to 60 cm. Only in cooler production areas is trellising considered. In hotter areas where Valencia oranges and grapefruit are produced, spacings of 7 x 3 meters or 6 x 3 meters are commonly used, whereas in cooler areas where Navel oranges, Clementines and Satsumas are produced spacings are 6 x 3 meters or as close as 4.5 x 2 meters. Virtually all citrus orchards in South Africa have windbreaks, with Casuarina cunninghamiana Miq. most commonly used. Undertree microsprinkler irrigation systems are the most commonly used method of irrigation, while some orchards still use overhead sprinkler irrigation. More recently however, drip irrigation systems have become increasingly common with an increased use of drip fertigation where pH and electrical conductivity are controlled in a balanced nutrient solution is provided daily to restrict root system development in a bid to control tree phenology. The hotter, more humid regions of South Africa are cursed by a spring and summer pest complex which can ruin an otherwise blemish-free crop in a relatively short time. The main problem is citrus thrips on young fruitlets necessitating the use of chemical control, thereby upsetting the natural enemy balance and causing repercussions of other pests, e.g. mites, later in the season. Organophosphate resistant red scale is a problem throughout. Mealybugs pose particular problems, whereas fruit fly (Mediterranean and Natal) and false codling moth can be problematic in many regions in specific years. There is a concerted move towards IPM programs, introduction of predators and minimum chemical intervention. Soil-borne diseases are principally due to Phytophthora root rot and citrus nematode, and citrus black spot and Alternaria brown spot are the foliar diseases of commercial importance in the sub-tropical regions. INTRODUCTION South Africa currently ranks 12th in world citrus production, producing approximately 2.3 million tons of citrus in 2007/08.

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Yet, South Africa is the second largest exporter of fresh citrus in the world after Spain with 1.3 million tons exported in 2007/08 comprising 61% of the total marketable citrus crop (CGA, 2009). The latter clearly indicates the importance of the fresh export market as the principal component of the South African citrus industry. The Southern African citrus-producing region comprises four countries, viz. South Africa (±95% of total production in the region), Swaziland (