Citrus Nursery Industry in China
: Houjiu Wu, Taisheng Li
: Citrus Research Institute,Chinese Academy of Agricultural Sciences (SW University)，Bei Bei, Chongqing, China 400712
Biocontrol in the Citrus Nursery
: Roger Smith
: General Manager of TreeSource Citrus Nursery
New Cultivars and the Challenge on the Obtention, Distribution and Commercialization.
: Luis Fernandez, Verena Müller, Veronica Herrera*
: ANA (Andes New Varieties Administration & Estación Experimental La Palma – Pontificia Universidad Católica de Valparaiso).
The Effects of Using a ‘Midnight Valencia’ Interstock on the Vigour of ‘Nadorcott Mandarin’, at Nursery Level
: Scott McKenzie1, Jade North2 and Paul Cronje3
: 1Cederberg Tree Nursery, Citrusdal, South Africa 2Department of Horticulture, Agricultural Sciences, University of Stellenbosch, South Africa. 3Citrus Research International, Department of Horticulture, Agricultural Sciences, University of Stellenbosch, South Africa
Nursery and field evaluation techniques for new citrus varieties in Australia
: Sanderson GP1, Monks DP1, Witte, TD1, Herrmann T2
: 1Dareton Primary Industries Institute, New South Wales Department of Primary Industries, Dareton NSW, Australia; Auscitrus, Dareton NSW, Australia
The Australian citrus industry, Horticulture Innovation Australia and New South Wales Department of Primary Industries (NSW DPI) has supported an independent citrus variety evaluation program since 2001. The aim of the program is to rapidly evaluate new citrus varieties introduced to Australia from overseas breeding and selection programs along with locally identified natural mutations.
The majority of new varieties now entering Australia have some form of Plant Breeders Rights protection and are controlled by variety managers. The majority of these managed varieties are evaluated at the NSW government core site of Dareton Primary Industries Institute. When a new variety leaves Australian Post Entry Quarantine it is held at the NSW DPI facility of Elizabeth Macarthur Agricultural Institute, Camden, NSW. The variety then goes to an insect proof facility at Auscitrus for budwood multiplication with a limited number of buds also supplied to NSW DPI for evaluation purposes.
The first part of the evaluation pathway is to propagate trees on a range of rootstocks to create enough budwood for top working onto mature Valencia trees. The potted nursery trees are also encouraged to set fruit for assessment of ‘trueness to type’. The top worked trees are established by bag enclosed bark grafting, Buddy-Tape wrapped bark grafting and chip budding Valencia regrowth.
Often a combination of all 3 is used on the one tree to ensure that at least one of the top working techniques is successful. The first assessable field grown fruit is usually available 3 years from top working. Information collected includes fruit quality, phenology, maturity period, fruit yield per tree and potential production issues.
Fruit is presented to citrus growers, variety managers, marketers and field walks conducted for approved groups to view top worked and young trees.
Citrus nursery management and production practices in Pakistan
: Khurshid T1, Donovan NJ2, Bowes J3
: 1Dareton Primary Industries Institute, New South Wales Department of Primary Industries, Dareton, NSW, Australia; 2Elizabeth Macarthur Agricultural Institute, New South Wales Department of Primary Industries, Camden, NSW, Australia; 3Victorian Citrus Farms, Red Cliffs Vic, Australia
Pakistan is an important global producer of mandarin fruit. Most citrus nurseries use traditional production practices.
There is a lack of healthy nursery stock available to industry, poor survival of nursery trees when transferred to the field, and a skill shortage in Pakistan’s nursery sector for developing best practice production systems.
The improvement of citrus nursery practices was identified as important for future development of the citrus industry in Pakistan. From 2007 to 2015, citrus work was funded by Australian Aid under the Australia-Pakistan Agriculture Sector Linkages Program (ASLP) managed by the Australian Centre for International Agricultural Research (ACIAR).
Australian and Pakistani collaborators established model screen houses for the production of high health status and true to type citrus germplasm of existing citrus cultivars, and new cultivars introduced from Australia.
Practical nursery management training was delivered to Pakistani nurserymen, service providers and researchers in Pakistan, Thailand and Australia. The team collaborated with Pakistani Hoslamand Khawateen Network (PHKN); a non-government humanitarian agency focussed on providing opportunities for women. Nurserywomen from the Khyber-Pakhtunkhwa province were trained in citrus propagation enabling them expand their existing, home-based, nursery business. A nursery training package was specifically developed for citrus nurseries in Pakistan but could be adapted for other developing countries.
Adoption of practical, low-cost changes has led to improved production and economic gains in selected nurseries and improved survival of trees during orchard establishment.
“The Inter American Citrus Network: 26 years at the Service of Citriculture in the Américas”
: Dr. María del Carmen Pérez Hernández1 Lic. Horacio Mederos Acosta2 Dra. Lochy Batista Le Riverend2
: 1. General IACNET Coordinator 2. Secretariat of Information and Communication
The Inter American Citrus Network (IACNET) is a technical collaboration network from the FAO, founded on April 18th, 1991, based on the importance citrus production had on world production. Its first General Coordination rested upon Brazil; in 1994, it was decided that Cuba took up that responsibility, function that has held so far. This presentation summarizes the activities of the Network since its creation highlighting its mission, general objectives, composition and current structure. Emphasis is done on the Course-Workshop the Production of Citrus Certified Budwood Material and the Project Improving production of citrus planting material in the Caribbean Basin (2007-2011) submitted through the Intergovernmental Group on Citrus Fruits from the FAO and financed by the United Nations Program for Development (UNDP) and the Common Fund for Commodities, respectively. Reference is made on their impact on the citricultures of some member countries, particularly Cuba’s. A summary of the impact other training actions on high-impact pests and diseases have had on continental citriculture, is provided. Finally, the collaboration of world reputed scientists is acknowledged.
The Identification Technology of Citrus Seedling
: D. Z. LI1,3 , Z. J.LIU2 , L.CHEN2,Y.YI2 , Y.T.ZHENG1 and Z. N. DENG1,3
: 1 National Center for Citrus Improvement, Hunan Agricultural University, Changsha, Hunan 410128, P. R. China; 2 Hunan Tenon Technology Service Co.,Ltd, Changsha, Hunan 410128, P. R. China; 3 Corresponding author
The production process of citrus seedling is complex, long period, and the species marker is unclear. Its disorderly production led to market chaos, unable to guarantee the quality to the buyer, and bring a series of problems to the administration. Our team developed identification technology of citrus virus-free container seedling by using RF radio frequency technology. The technology includes three parts: 1. electronic chip receive and feedback signal; 2.the development of implantation tool; 3.Code sweep device accept the feedback of the information. The chips were implanted into the citrus container seedlings, during a year and a half of testing, chips work smoothly,and the growth has no significant difference between implant seedlings and CK. The technology can be applied to the certification of original virus-free seedling and traceability of seed quality safety.
Successful Propagation of Rootstocks with Stem Cuttings
: Bowman KD1, Albrecht U2, Niedz RP1
: 1US Horticultural Research Laboratory, USDA, ARS, Fort Pierce, FL, USA; 2Southwest Florida Research and Education Center, University of Florida/IFAS, Immokalee, FL, USA.
Citrus rootstocks can be propagated effectively using stem cuttings in a greenhouse mist-bed system. We have worked with methods for rooting of stem cuttings over several years, and have refined a system to reliably provide efficient propagation for a wide range of common rootstock genotypes. Greenhouse studies demonstrated that a key factor in the rooting of citrus cuttings, and early growth of those cuttings, is the leaf area on the initial explant. This effect appeared consistent across genotypes, with a larger explant leaf area providing the combination of highest proportion of cuttings that rooted and the best growth from the resultant plants. Studies also indicated that explants from juvenile (non-fruiting) clones rooted much better than explants from mature (fruiting) plants of the same cones. Efficiency of rooting shoot explants of seven important Florida rootstock cultivars, Swingle (Citrus paradisi × Poncirus trifoliata), Cleopatra (C. reticulata), US-802 (C. grandis × P. trifoliata), US-812 (C. reticulata × P. trifoliata), US-897 (C. reticulata × P. trifoliata), and US-942 (C. reticulata × P. trifoliata) was compared in a repeated study using the described mist-bed system. Shoot and root development of the resultant plants produced from stem cuttings was examined at 20 weeks of age and observed to be of good quality for continued nursery growth and budding.
Citrus Nursery Scene in Australia
: Herrmann T
: Auscitrus, Dareton NSW, Australia.
The Australian nursery industry is small by international standards but faces similar threats and opportunities as other developed countries. The increasing cost of labour is universal, and minimum wage standards and workplace legislation impose considerable cost pressures on Australian nursery trees. This is forcing the adoption of more modern and efficient production methods as nurseries endeavour to reign in input costs, with the majority of production containerised. With its affluent society and favourable weather there is a strong market in Australia for garden plants and backyard citrus is a significant component of the nursery industry, which also poses additional biosecurity risks. While Australia is free of devastating diseases such as HLB/ACP and Canker the pressure on our borders is increasing, and biosecurity awareness is a strong focus for both the citrus and nursery industries combined. This is hampered by the lack of a legislated mandatory nursery tree certification program, with the Australian seed and budwood scheme being widely utilised purely on a voluntary basis. The citrus industry, nursery industry, state and federal governments all work together to form a unified system to protect our healthy industry.
The Australian Citrus Industry
: Nathan Hancock
: Citrus Quality and Market Information Manager for Citrus Australia
There are around 1,500 citrus businesses operating across Australia’s mainland states and the Northern Territory. The industry produces approximately 620,000 tonnes annually on 25,000 hectares, with a gross production value of over $500 million. Of the 620 000 tonnes produced, between 200,000 and 250,000 tonnes are processed into juice, with the remainder being sold for fresh consumption on domestic and overseas markets. The production trend is increasing over the past 5 years as new plantings of mandarin come in to bearing.
Orange is the dominant citrus type, navel orange (9,200ha) being the larger category followed by Valencia and other juicing types (6,591). Valencia production has been in decline for several years as the profitability of the processing varieties declined. Navel production is dominated by mid-season (2,600ha) and late navel (4,500ha) varieties. Orange production is predominantly through the ‘tristate area’ comprising the Riverina region in New South Wales (7,300ha), the Sunraysia region in northern Victoria and southern New South Wales (4,859ha) and the Riverland region in South Australia (5,344ha).
There has been a significant increase in mandarin production in Australia. Total area is 6,200ha up from 5,310ha in 2014. The mandarin category is dominated by three main varieties, they being Imperial (1,648ha), Murcott (1,849ha) and Afourer (1,454ha) with approximately 30 other varieties making up the 1,247ha balance. Imperial mandarin is a willow leaf type mandarin that is popular with the domestic market but has very little export potential due to the soft characteristics of the fruit. Afourer is known in other countries as W. Murcott and Nadorcott. Mandarin production is predominately in the central part of Queensland (3,249ha) followed by the Riverland (1,200ha) and the Sunraysia region (1,000ha).
Production forecast trends indicate a significant increase in mandarin and lemon volumes based on current planting rates whilst navel production forecast has plateaued and juicing oranges are in significant decline.
Australia exports citrus to over 30 countries worldwide. The United States was once the leading market for Australian citrus exports. Since peaking at $60 million in 2007, Australian exports to the United States have been in decline, largely due to increased competition from other southern hemisphere suppliers and unfavourable exchange rates. However, with Australia’s close proximity and an expanding middle class in Asia, there has been a strong shift in focus in exports to Japan, China, Hong Kong, Indonesia, Malaysia, Singapore, Thailand and the Philippines. Exports to the subcontinent, the Middle East and the Pacific (including New Zealand) are also significant.
Value of Australian citrus exports averaged AU$198 million over the previous 10 years, with a new high achieved of AU$328 million in 2016. Value of citrus exports have doubled since 2006 (AU$163 million) and have been particularly strong in the 2015 and 2016 seasons. The average 10 year citrus export volume is 160,000 tonnes with a record volume of 220,000 tonne in 2016.
Citrus variety development: From experimental to commercial
: Graham H. Barry
: XLnT Citrus company, Somerset West, South Africa
Variety Development entails the direct or indirect (via third party) breeding and creation of new varieties in conjunction with their evaluation until release. Variety Management entails the administration and coordination of the various functions involved with the sourcing and introduction, further evaluation, and commercialisation of new varieties.
Variety Development and Variety Management are specialised fields requiring a thorough knowledge of varieties, their characteristics, climatic adaptability, specific production requirements, as well as the processes involved in the development and management of varieties (breeding, evaluation, commercialisation), and intellectual property (IP) management. Variety Management is typically not a public function (except in cases of managing their own varieties), but is driven and directed by private enterprise.
Variety Development, however, has historically been a public function, e.g. USDA, UC-Riverside, University of Florida, IVIA-Spain, Volcani-Israel, University of Catania-Italy, CSIRO, QDPI, etc. More recently, however, citrus variety development has started to shift towards private entities. In other fruit crops, e.g. table grapes and stone fruit, breeding and variety development is conducted by more and more private enterprises, e.g. SunWorld, International Fruit Genetics, Bradford Genetics, Kingsburg Orchards, etc. Citrus variety development and management is moving in the same direction – certainly citrus variety management is already largely, if not exclusively, in private hands, e.g. Biogold, Future Fruit, Citrus Genesis, etc., while breeding and variety development has remained a public function in the USA, but not so in Spain where nursery groupings or grower-packers, e.g. AVASA, GCM, Citrus Genesis and others, are directly involved in mandarin breeding. Note that “access to” new varieties is the crucial element and may be implemented under different scenarios: i) exclusive access, ii) preferential access, or iii) open access (open to all interested parties). The key focus areas of the operational side of variety management are: i) to identify the specific fruit characteristics to pursue, ii) to breed new varieties, iii) to import or introduce new varieties, iv) to evaluate (production and market) new varieties, v) to commercialise new varieties, and vi) to manage IP related to variety development.
Global trends in citrus varieties
: Graham H. Barry
: XLnT Citrus company, Somerset West, South Africa
Whereas global citrus production increased at a very slow rate [1.7 % per annum over 6 years; 121.3 million tons in 2014 (FAO, 2016)], mandarins have shown tremendous annual growth of 5.9%, grapefruit/pummelos production had 2.6% annual growth mainly due to 67% increase in pummelo production from China, whereas Florida’s grapefruit declined by almost 30% (2008 to 2014), lemons/limes had a 1.5% annual growth in production, and oranges showed only 0.25% annual growth in volumes although oranges continue to dominate global production (57%) and exports (44%), followed by mandarins (26% and 31%) which has gained market share at the cost of grapefruit/pummelos (6.4% of exports). Overall, the mandarin category has enjoyed the most growth, particularly in China, Morocco, Turkey, California, Egypt, Peru and South Africa, with a decrease for Argentina; growth in mandarin volumes is largely attributed to +60% increase in China, as well as significant plantings of Nadorcott and its derivatives in the afore-mentioned countries.
New mandarin cultivars continue to be developed and released from citrus breeding programmes on every continent and will gradually make an impact on global citrus trends, but adaptability to climatic conditions remains a challenge. Grapefruit production in the different production regions of the world is typically dominated by specific varieties, e.g. Star Ruby in South Africa and Israel, Rio Red in Turkey and Texas, and although new variety development can be seen in Florida (FL-904 grapefruit-pummelo hybrid with low FCs) and Texas (Texas Red grapefruit), there has been relatively little recent innovation in new grapefruit cultivars. Lemons and limes continue to be dominated by the established cultivars, although seedless lemons (Eureka Seedless) from South Africa and Australia have started to make in-roads.
Since oranges cannot be bred by conventional breeding techniques, new orange variety development is driven by the selection of natural mutations and is thus a slow, step-wise process; among the Navel oranges the ultra-early M7 from Australia has recently seen increases in plantings, as well as various late-maturing Navel orange selections; similarly for Valencia types, local selections largely predominate.
Light and Chemical Treatments to Improve Shoot Growth of Newly Budded Citrus Nursery Plants
: Bowman KD, Niedz RP
: US Horticultural Research Laboratory, USDA, ARS, Fort Pierce, FL, USA
In nursery production of citrus trees, uniform and rapid growth of the scion on newly budded rootstock liners is critical for efficiency of management and the timely availability of field ready trees. Some rootstocks have been noted to be especially difficult to obtain good shoot growth of newly budded plants, and recalcitrant shoot emergence and growth is especially common during the short days of winter. We have conducted a multifactorial experiment to evaluate the influence of several factors on bud survival, emergence and early growth of budded plants, with a goal of determining what treatments will be most useful to improve these characteristics in the nursery system. The study made use of the rootstock US-802 (Citrus grandis × Poncirus trifoliata), a rootstock with considerable commercial importance in Florida (USA), but which has been observed to often yield delayed or erratic bud emergence from recently budded plants. The study was also conducted during the period of the year when daylight was not optimum for citrus growth. Factors studied for their effects of shoot growth and emergence were compass orientation of the budded plant, use of supplemental light-emitting diode (LED) or metal halide lighting, and bud treatment with ethanol or water-based solutions containing 6-benzyladenine (BA), Tween 20, and/or dimethyl sulfoxide (DMSO) at various concentrations. Significant differences were noted in the effects of these treatments on scion bud survival and emergence, scion shoot elongation, node length, and leaf area, and the number of sprouts on the rootstock. The relative importance of each of the manipulated factors on nursery performance of the budded trees will be described and discussed
INNOVATION STRATEGY OF CULTIVARS AND ROOTSTOCKS FOR THE CHILEAN CITRUS INDUSTRY
: Ortúzar, J.E.
: Valenzuela M. Chilean Citrus Committee
The Chilean Citrus Industry has experienced a deep transformation over the last 20 years. Export orientation shifts on the main Citrus categories have led to a whole new variety and rootstock scenario. Export yields and Although the change of varieties has been a key factor to support the success of Citrus exports during this period, the innovation trend seems to have slowed down as the dominant varieties and rootstocks have consolidated.
The Chilean Citrus Committee is an industry board created to help the development of exports by coordinating promotion efforts, market access and research activities. With regard to the introduction and development of new varieties, the Committee has maintained a degree of neutrality, in the assumption that breeders and their representatives are working directly with the exporting companies, addressing the development of new varieties at their own pace.
With regard to new rootstocks, there are many challenges that the industry agents seem less motivated to do on their own. New rootstock research seems less urgent when no serious pest or disease emergency at stake and needs many years of experience before demonstrating consistently the performance under different soil and climatic conditions. For this reason, the Citrus Committee is funding and promoting research efforts on new rootstocks to address some of the challenges that have been identified.
Nematode susceptibility and replant problems of Citrus macrophylla remain as the most critical problem of lemons, for which there is no replacement for C. macrophylla. Fruit quality and productivity per m3 of canopy are key to new rootstocks for Navels and Mandarins to match Poncirus trifoliata traits.
Nursery industry can play a key role supporting the innovation of both varieties and rootstocks and the cooperation and enthusiastic input of nurseries with the growers and the Citrus Committee can help speed up the identification and study of new promising rootstocks that are needed to improve the competitiveness of the industry.
Citrus Nursery Trees Certification System in Brazil, ISO 9001-2008.
: Christiano Cesar Dibbern Graf1, Rafael Augusto Fadel Bordignon2
: 1Citrograf Mudas, Vivecitrus 2Citrograf Mudas, Quality Manager
The Brazilian citriculture growing requirement for high-quality citrus trees with phytosanitary control and a known genetic source led Citrograf Mudas, together with Vivecitrus, to develop an ISO 9001-2008 Citrus Nursery Trees Certification System for the whole citrus trees production chain, including production of seeds, rootstocks, budwoods and trees, in order to produce and market healthy citrus trees, following strictly the phytosanitary legislation for the production of citrus trees in Brazil, in the State of São Paulo, and also in accordance with ISO 9001-2008 standards.
The production practices used in the composition of this ISO 9001-2008 Citrus Nursery Trees System Certification were based on the pertinent legislation, associated with production practices used in several production sectors, mainly in the food industry, where prevention of food contamination in the production process is a critical factor to ensure product quality. Processes were set to ensure the phytosanitary quality of the trees produced, which involve pest and disease monitoring and strict control, as well as disinfestation of any and all material entering the production system, control of people’s entry, including employees, where they all wear uniforms provided for the company. Based on all these factors, Citrograf Mudas has opted for ISO 9001 Certification for its production process, which began based on ISO 9001:2008 standard, being in transition to ISO 9001:2015. To ensure the Certification System is maintained, and therefore the high quality of its trees, Citrograf Mudas has always sought to achieve its Quality Goals, which are to secure its clients’ satisfaction, meeting their requirements, keeping all staff trained to develop their activities, establish and continuously improve the production process of citrus trees, and participate in events of information and technology diffusion, and this way, following its Quality Policy, supporting the production of citrus trees of high genetic and phytosanitary quality, and the future of the Brazilian citriculture.
The Eternal Tale of the Dragon and the Phoenix: Current Chapter on Citrus Greening Disease in Florida
: Fred G. Gmitter Jr.
: Citrus Research and Education Center University of Florida-IFAS
Huanglongbing (yellow dragon disease) has wreaked havoc on the Florida citrus industry since the first symptomatic trees were found in 2005. Production has been decreased by nearly 70%, many citrus farms have been abandoned, packing houses have closed sometimes after nearly 100 years in existence, and juice plants are operating at far below capacity.
The Dragon, indeed, has visited Florida, and unlike the Asian perspective of good fortune associated with the beast, there is not much good to be seen; devastation and ruin color the Florida citrus landscape. In Western mythology, the Phoenix arises from the ashes of destruction, and a new time comes to pass; Eastern philosophy views the Phoenix as immortal, associated with times of peace and prosperity.
The Florida industry is looking for hope, and perhaps genetic improvement strategies will lead to the return of the Phoenix. An overview of recent history in Florida citrus, and progress made in research and on citrus farms, will be presented to fill in the details of this current chapter of the story.
The University of Florida-CREC Breeding Program: New Scion and Rootstock Cultivars
: Fred G. Gmitter, Jr., Jude W. Grosser, and William S. Castle
: Citrus Research and Education Center University of Florida-IFAS
In the last ten years, the breeding team at UF-Citrus Research and Education Center has released several dozen new scion and rootstock cultivars for the Florida citrus industry. Some of the cultivars are being made available internationally, as well.
The UF program is one of only a few breeding citrus in subtropical conditions and under extreme disease pressure. The wide range of breeding approaches available (sexual and somatic hybridization, cybridization, somaclonal variant selection, etc.) has been utilized to create new rootstocks, oranges, mandarins, grapefruit, acid fruit, and some novelty types.
The characteristics of some of the more interesting cultivars, particularly those being commercialized now, will be highlighted.
Soil substrates for certified organic citrus nursery trees.
: Klaus Bederski
: Vivero Topara
The Topara Fruit Tree Nursery in Peru, part of a larger farming operation, ventured into organically grown trees because of economic necessity and not because of romantic reasons. The world-wide El Niño Weather event of 1997-98 had destroyed the farm, nursery included.
Ability to honour post-disaster financial obligations forced the company to search for added value in its export products. This was successfully done but challenged the nursery to also convert to organic. An adequate soil mix for good root systems in container grown plants is the starting point for grade ¨A nursery trees in all species. This paper describes the concepts and procedures that, under the specific conditions of the location of the Topara Nursery, have allowed it to produce trees with excellent root systems .
Topara Trees have received organic certification for over 15 years. Procedures to prepare organic composts, humus and liquid plant nutrients are described. Soil mixes for seed beds and for final container grown plants are indicated and root systems of citrus rootstocks and of other fruit tree species are shown at different stages of growth : seedlings out of seed-beds , rootstocks prior to budding, trees ready for sale.
Profits = high % of grade ¨A ¨ trees produced in the shortest time
: Klaus Bederski
: Vivero Topara
There are technical and administrative challenges associated with the profit making objective of all nurseries world-wide. The technical challenges are well known by all nurserymen and briefly described: good seed, seedbeds, nursery rows. Early planting and budding. Good nutrition and phytosanitary control. Early staking of the developing trunk to be ready to sell the tree as a ¨whip ¨ or, a few months later, as a fully grown tree with 2,3, or 4 mature branches.The administrative challenge is to obtain the desired technical results with the lowest possible loss of trees along the way, and in the shortest time. It includes climatic and phytosanitary infrastructure that is required in many locations of the world, in a few not yet.
Above all, it includes good record keeping at all stages and permanent inventory control at all stages of the growing process of nursery trees. This paper aims at initiating an open exchange of ideas on how this is being done by representatives of assisting nurserymen.
Supply of healthy propagating material to Australian citrus nurseries
: Donovan NJ1, Herrmann T2, Jelinek SM1, Chambers GA1, Englezou A1
: 1Elizabeth Macarthur Agricultural Institute, New South Wales Department of Primary Industries, Menangle NSW, Australia; 2Auscitrus, Dareton NSW, Australia.
The foundation of a productive orchard is the use of high quality propagation material that is true-to-type and has a high health status. Many citrus diseases are graft-transmissible; they can cause stunting, yield loss and even death in some scion and rootstock combinations, yet other citrus varieties may be symptomless carriers. For most graft-transmissible diseases, symptoms will not be seen in nursery trees, the signs will appear a few years later in the orchard. By that time, the disease may have spread to surrounding trees through root grafting or on cutting tools. Nothing can be done to save infected trees; you need to pull the trees out and replant.
In Australia, the Auscitrus propagation scheme supplies budwood and rootstock seed to industry from trees that have been tested for graft-transmissible diseases by the citrus pathology team at the New South Wales Department of Primary Industries (NSW DPI). The NSW DPI testing service is supported by research to ensure the most efficient and sensitive diagnostic tests are used. Auscitrus also checks budwood source trees for trueness to type and maintains budwood source trees in a secure facility where all pest and disease issues are managed to the highest standard.
Budwood shipments can be traced beyond the source trees, back to the original mother tree held in the National Citrus Repository. New variety imports and local selections are maintained as ‘foundation trees’ in insect-proof repository houses (matching houses in 2 locations) and tested regularly to ensure their high health status. The widespread use of good quality propagation material of a high health status has helped to reduce the incidence of graft-transmissible diseases in Australia. When combined with improved cultural practices and the use of disease-tolerant rootstocks, citrus orchards have the ability to achieve their full productive potential.
Seedling and cultivar selection.
: Ian S. Tolley OAM
: Horticultural Consultant
Two areas of citrus nursery tree production that requires special attention.
Failure to adopt positive steps to incorporate both as important standards, have long term consequences and a potential to shred reputations.
A segment of the history of ISCN, created in 1980, and of Albert Newcomb’s fundamental effect on the current citrus nursery industry.
The potential role of ISCN members looking at wider implications of involvement and participation in the citrus industry.