Citrus
Nasir Ayub
Group Members
Department:
Food Science UOS

Introduction
• Origin: South East Asia
• Family: Rutaceae
• A prized fruit of Pakistan
• Ranks 1st among all fruits
• Shares 34% in total fruit production
• Shares one-third of total value of fruit’s exports
• 95 % kinnow Produced in Punjab

Classification
• Swingle (1943) divided the genus citrus into 3
independent genera:
1. Citrus included 16 species
2. Poncirus include 1 species
3. Fortunella include 4 species
• Hodgson (1961) divided citrus into 36 species.
• Mostly Swingle classification is followed with some
modifications suggested by Hodgson.

• Family: Rutaceae
• Sub Family: Aurantioideae
• Sub family consists of 2 tribes:
• Clausenae and Citreae
• Citreae has 33 genera including
• Citrus (Sweet orange, mandarin, grapefruit, lime and lemons)
• Poncirus (kumquat)
• Fortunella (trifoliate orange)

Distinguishing features of 3 genera
Genus Citrus:
• Unifoliate
• Ovary has 8 or more cells
• Evergreen trees and shrubs
• Spiny with thick, leathery leaves and winged petioles
• Flowers are white or in some species pink on the outside, Pentamerous, axillary
and scented.
• They have small calyxes, hard sepals and thick petals with densely spaced oil
cells.
• The stamens are numerous (15-60) and the ovary superior with 8-15 carpels
containing few to several ovules
• Fruit has thick leathery rind, botanically it is a special type of berry called a
hesperidium.
• Fruit is globose, sub-globose or elliptical filled with juice sacs or vesicles.
• Fruit contain few to many white or light green seeds, which are generally
polyembryonic.

Distinguishing features of 3 genera
Genus Citrus: is divided into two sub-genera
1. Eucitrus: all edible citrus species
2. Papeda: contain acrid oil droplets in the juice vesicles
and are inedible

Distinguishing features of 3 genera
Few important commercial citrus species are:
Citrus sinensis (L) Osbeck----Sweet Orange
Citrus reticulate Blance----Mandarin
Citrus paradisi Macf. Grapefruit----(Pomelo)
Citrus grandis (L) Osbeck Chakotra---(Pummelo)
Citrus limettioides Tan.----Sweet lime
Citrus aurantifolia Swing----Kaghzi Lime
Citrus limonia (L)----Lemon
Citrus medica (L)----Citron
Citrus aurantium (L)----Sour orange
Citrus jambheri Lush----Rough Lemon

Distinguishing features of 3 genera
Genus Poncirus:
• It has only one species P. trifoliate Raf.,
• Compound leaves with three leaflets
• Deciduous
• Tree is small and spiny
• Flowers are sessile, and borne on previous-year wood in
the axils of spines. They open wide and flat and are creamy
white.
• The inedible, pubescent fruit has 6-8 segments, is filled
with smooth seeds and is orange-yellow at maturity.
• Poncirus is generally used as a rootstock in colder regions
and for growing dwarf trees.

Distinguishing features of 3 genera
Genus Fortunella:
• It has four species, of which the commercially important
ones are F. margarita Swing. (oval kumquat) and F. japonica
Swing. (round kumquat).
• The trees are small with small green leaves paler on the
other side.
• The flowers are white and smaller than those of citrus
• Fruit is small, orange colored, 3-6 celled, acidic and juicy but
with a sweet and edible rind. The other species are F.
crassifolia Swing and F. hindsii Swing.

Hybrids
Hybrids Parents
Citranges Poncirus × sweet orange
Citrangesquats Citranges× fortunella
Tangelos Mandarins × grapefruit
Limequats Lime × fortunella
Citrumellos Poncirus × grapefruit
Citrandrins Poncirus × mandarins
Kinnow Nobilis ×deliciosa

Soil
• Deep sandy loam, loam and clay loam
• pH: 5.5-8.5
• Subsoil should be free from hard pan, sticky clay and
water logged conditions
• Poor soils with high pH are not suitable
• Soil requirements depend upon the type of rootstock
used for various species and varieties.
• Rough lemon is a good rootstock for dry, sandy loam
soils of Punjab, whereas sour orange performs better
on the moist and heavy soil of NWFP.

Climate
• Tropical and Sub Tropical
• Up to 450-750m elevation
• Temperature is an important factor. In cool regions,
vegetative growth is less, fruit growth is slow, ripening is
delayed and fruit is acidic. In colder regions, pigmented
cultivars like Red Blood sweet orange develop excellent
quality.
• Temperature range: 13-40°C
• Can endure 0-2°C without injury, depending on the cultivar
and duration of cold period.
• Grapefruit is the high temperature resistant citrus sp.
• Extreme cold and frost can burn flowers and young twigs.

Climate
• Species appear to resist frost in the following
descending manner
• Mandarin, sour orange, sweet orange, chakotra, grape
fruit, sweet lime, lemon, kaghzi lime and citron.
• In hotter regions, trees produce more growth and fruit
grows faster and ripens earlier but fruit may suffer
from sunburn
• In Pakistan, the central divisions of Punjab– Sargodha,
Faisalabad, Lahore and Multan---produce excellent
citrus.
• In NWFP, Peshawar, D.I. Khan and Dir are important
citrus producing areas.

Temperature Requirement
• Seed Germination:
15-30°C
• Vegetative Growth:
Optimum shoot growth: 25-31°C
Optimum root growth: 25-26 °C

Flowering
• Season:
February- March
• Lemon:
Throughout year, when growing in coastal
regions with mild winter
Spring, when growing in dry areas with hot
summer and cold winter

Fruit Set
• Optimum Temperature for pollen viability:
15-20°C
• Pollen tube growth is temperature dependent
• High temperature causes poor fruit set

Propagation
• Sexual:
Seeds
• Asexual:
Budding
Layering
Grafting

Planting Seasons
• Spring
February- March
• Autumn
September-October

Citrus Nursery
• Extraction of seeds
• August- September
• Storage of seeds
• Preparation of seed bed
Length 5-6 ft
Width 3 ft
Height 6-9 inch
Distance from seed to seed 4-6 inch
Use fungicides and depth of seed should be 1 cm

• Transplantation of seedling:
• Seedling should be transplanted after 6-12 month
• Plant to plant distance 6-9 inch
• Row to row distance same as plant to plant distance
• Please left some space empty after four lines
• Care of seedlings
• Budding and grafting of seedlings
• Selection of scion wood, preparation of rootstock
• Aftercare of budded/grafted plants

Recommended Propagation
Techniques
Fruits Recommended Methods
Sweet Orange, Mandarin T-Budding, T-Grafting
Grapefruit and Eureka Lemon T-Budding
Sweet Lime Stem cutting
Khaghzi Lime Layering

Time of Fertilizer Application
Nutrients and Doses Time of Application
FYM Dec-January
1/3 N + P + K (full dose) Before flowering (Feb)
1/3 N At pea stage
1/3 N In August
Micronutrients Foliar application in Feb

Planting Geometry
• Square System
Planting distance: 22´ to 25´
64-90 plants/acre
• High Density Plantation
R×R: 10 ft
P×P: 10 ft

Intercropping
• From 1-6 yrs of age: short stature crops with
shallow root system are allowed to grow
Mung, Mash, Masoor, Peas
• Exhaustive crops with deep root system are
not allowed to grow
Sugarcane, Cotton, Wheat
• Afterwards clean cultivation is recommended
• No hoeing or cultivation except once in a year
to kill the weeds.

Irrigation
Over irrigation is more injurious than under
irrigation in citrus
• Surface irrigation
1. Basin system
2. Modified basin system
3. Flood irrigation
• Sprinkler irrigation
• Drip irrigation

Irrigation Schedule
Season/Month Irrigation Frequency
Spring (Feb-March) Once a month
Summer (April-July) Twice a month
Monsoon (August) Subject to rainfall
Autumn (Sept-Oct) No irrigation
Winter (Nov-Jan) Once a month

Precautions in Applying Irrigation
• Irrigation water may not be allowed to touch
directly to the stem of citrus tree
• Field and water channels should be precisely
leveled
• Stop irrigation at flowering time
• Stop irrigation two weeks before harvesting
• Restrict irrigation in Oct-Nov
• Light irrigation during frosty nights

Determination of irrigation
• Fruit growth
• Wilting symptoms
• Tensiometer

Tensiometer

Pruning
• For establishment of strong well balanced framework
• Facilitate management practices like spraying, picking
etc.
• To ensure balance between vegetative vigor and
fruitfulness
• To improve penetration and increase the set of inferior
fruit
• Increase soluble solids and improve rind color
• To produce new and productive wood
• Tree age 70-100 years California due to pruning

Physiological Disorders
• Alternate Bearing
• Unfruitfulness
• Fruit Drop
• Granulation

For disease there is some specific causal
organism and which can be corrected
It is very hard and difficult to correct/control
the physiological disorder

Alternate Bearing
Nutritional imbalance
Varietal character
Mandarin
Sweet orange
Grape fruti
Kinnow , Wilking
V.late, W. Navel
Mardh seedless,
1. Heavy manuring during off year
2. Fruit thinning during on year
3. Delayed harvesting during off year
4. Early harvesting during on year

Unfruitfulness
 Physiological or genetic causes
 Involve hormonal or nutritional imbalances
 Climatic factors
• Genetic or physiological
• Incompatibility
• Heterostyly
• Ovule abortion

Involve hormonal or nutritional imbalances
• General weakness may be removed by an
appropriate fertilizer program
• While excessive vegetative growth
• Withholding nutrition
• Root pruning or ringing of main branches
• Climatic factors
• Certain varieties refused to produce in particular
environments e.g Washington navel

Fruit Drop
Start from blooming and continue up to harvest
1 Flower drop
Bloom heavily---- thousand of flowers
Usually 95% drop and 5% set fruit
Fruit set % range form 1-4%
Reasons:
1. Climatic conditions
2. Weak plant, deficiency of nutrients
3. Mutual flower competition
4. Heavy winds, or rain fall

Fruit Drop
2- Initial fruit drop
Fruit drop after fruit set
Due to nutritional imbalance
Weak trees
3- June drop
1. Occurs in month of May and June
2. Natural load sharing
3. Drop of poorly developing fruits
4. Around 96% young fruit drop occurs in Pineapple
orange
5. Around 75% drop ----- in Kinnow

Fruit Drop
4- Pre-harvest drop
1. This drop is at mature stage
2. It is a commercial loss to the grower
3. Failure in auxins synthesis due to abscission
layer
4. Attack of insects and disease
5. Controlled with application of hormones
6. GA and 2,4-D, NAA etc

Granulation/Raciness
•The condition is characterised by large, hardened and
apparently dry juice vesicles
•The stem end of fruit is more effected as compared to
styler end
•Some time one half, one third or under extreme cases
whole fruit is affected
•It cannot be identified externally, because there is no
external abnormality
1. The cell wall of granulated vesicles are thick
2. Sugar contents are reduced then normal
3. Mineral content are increased then the normal

Granulation/Raciness
•Due to thick walls of fruit vesicles more minerals,
less sugar content it seems to be dry
•Granulation increase of harvesting is delayed
•Frequent irrigation or water standing in the root
zone for longer period of time may also increase
the incidence of granulation
Corrective measure
•Spot picking of larger fruits at earlier stage
•Large interval of irrigation
•Spraying of growth regulators

Granulation/Raciness

Major Diseases
• Phytophthora Gummosis or Foot rot
• Trunk Gummosis
• Damping off/ Root rot
• Wither tip
• Citrus Canker
• Citrus Greening
• Citrus Quick Decline
• Citrus Slow Decline

Citrus Canker
1- Citrus Canker (Xanthomonas compestris)
Bacterial disease
Appear on leaves, branches, fruit
a- Symptoms
1. Small yellow spots are formed on upper epidermis, then on lower
epidermis
2. Later, spots become bigger, brown, raised
3. Diseased area die and leaving hole
4. Spots also appear on twigs and fruit drop
Example: K lime, Lemon, Grapefruit, Sweet lime, Sweet orange
b- Corrective measure
1. Selection of healthy nursery plants
2. Prune the affected part and spray with bacteriaside

Citrus Canker
Citrus Canker on fruit
Citrus Canker on leaves

Citrus Withertip
2- Citrus wither tip (Colletotricum gloeosporioids)
Fungal disease
a- Symptoms
1. All aerial part, leaves, braches and fruit are affected
2. Wilting from braches from top to bottom
3. Branches looks silvery grey leafless
4. Leaf fall is common
5. Pathogen kill the plant
b- Corrective measure
1. Improve growing conditions of the orchard
2. Spraying with cu based fungicides

Citrus Withertip
Citrus withertip

Citrus Greening
• Causal organism was first considered as virus. Later evidenced as
mycoplasmal diseases and now classified as Ricketisa like organisms (RLO)
• Yellowing of veins and adjacent tissue
• Mottling of entire leaf
• Premature defoliation
• Die back of twigs and have shorter internodes
• Decay of feeder rootlets and lateral roots
• Decline and ultimate death of entire tree.
• Transmitted by grafting and Citrus psylla
• This disease is more severe on sweet oranges than on mandarin, acid lime
and grapefruit.
Control:
• Application of tetracycline-antibiotic
• Control of Citrus psylla

Citrus Tristeza Virus
• Vein clearing in lime
• Bronzing of leaves
• Stem pitting
• Twig and root die back
• Leaf drop
• Foliage wilt
• Sudden death
• Tree debilitation
• Reduced fruit size
• Necrosis of cambial tissue

Citrus Tristeza Virus
Control:
• Aphid contol
• Use of tristeza tolerant rootstock
• Eradication of all infected trees
• Use of virus free buds employed for budding

Insect Pests of Citrus
• Citrus psylla
• Citrus leaf miner
• Citrus fruit fly
• Lemon butterfly
• Citrus mealy bug
• Citrus thrips

Citrus Psylla Leaf Miner
Mealy Bug
Lemon Butterfly Weevil citrus leaf miner

Citrus Psylla
1- Citrus Psylla
Sucking types insect,
Adult are brown in colour, black antena,
Insect attack at the time of blooming
Attacked the fresh growth, which is important for fruiting in citrus
Corrective measure
Pre-bloom prophylactic spray of insecticides during January and February

Adult; Citrus Psylla
Nymph; Citrus Psylla

Citrus Leaf Miner
1- Citrus leaf miner
Chewing types insect,
Small silvery white insect with black eyes and wings fringed with hairs,
It make the tunnels in the leaves, which looks silvery white, Attack on young
nursery plants more
Corrective measure
Spray with insecticides during leaf emerging
Avoid using citrus hedges around citrus orchards or nurseries

Damage caused by citrus leaf
miner
Citrus leaf miner

Causes of Low Production
• High pH
• Low organic matter
• Saline soils
• Uncertain weather conditions during flowering (fog, frost,
rains)
• Use of unfit tube well water
• Faulty intercropping
• Inadequate and imbalance fertilizer application
• Poor plant protection measures
• Non judicious irrigation
• Low grade nursery plants
• Mechanical injury to the plants during hoeing and
ploughing

Suggestions (short and long terms)
1. Surveys
• Periodical assessment of disease status
• New areas
• New diseases
• Identification of priorities
• Characterization of viruses
2. Nursery Improvement
• Registration
• Phyto-sanitation, production of virus free stock
• Adoption of recommended horticultural practices

3. Production / Maintenance of High Quality
Nursery Plants
• Quarantine area
• Clean stock (mother trees, virus testing,
thermotherapy, indexing)
• Certification
• Economic evaluation
4. Improvement of Orchards
• Eradication of infected trees
• Horticultural practices

5. Insect- Vector Relationships
• Identification of vectors
• Transmission of viruses
• Population dynamics of vectors
• Search for predators and parasites of citrus
psyllids
• Sound, viable IPM

Promising Varieties of Citrus
SWEET ORANGE
• Musambi
• Pineapple
• Jaffa
• Blood Red
• Hamlin
• Washington Navel
• Valencia Late
• Salustiana
• Torocco
• Moro

Mandarins
• Kinnow
• Feutrell’s Early
• Honey Mandarin
• Fair Child
• Fremont
• Minneola
• Orlando

Grapefruit
• Marsh seedless
• Foster
• Duncan
• Shamber
• Red Blush
• Star Ruby
• Frost Marsh

Lemon and kumquat
• Eureka lemon
• Meiwa
• Naghmi

Research Centers/Inst.
• University of Agriculture, Faisalabad,
• Horticultural Research Center, Sahiwal,
• Orange Research Insitute Sargodha,
• Ayyub Agricultural Research Institute, Faisalabad,
• Barani Agricultural Research Institute, Chakwal,
• National Agriculture Research Center (NARC),
Isalamabad,
• Zarai Taraqati Bank Limited (ZTBL) Farm, Islamabad,
• Tarnab Agricultural Research Station, Peshawar
• Federal Seed Certification, Germplasm unit, Sherkhana,
Peshawar

Germplasm at Different Places in Pakistan
Total No. of Cultivars Scion Rootstock
210 156 56
Province Citrus Cultivars
Punjab 170
Federal Area 80
Khyber PK 46
Baluchistan 11

This number is a handsome to be used in our
citrus diversification program but still we have
failed to properly use this gene pool
information.

Citrus Cultivars at Different
Centers/Inst.
Centre/Institute Citrus Cultivars
Hort. Res. Station (Sahiwal) 170
U.A. Faisalabad 89
ZTBL Farm (Islamabad) 80
FSC Germplasm Unit Sher Khana, Peshawar 46
CRI (Sargodha) 43
AARI (FSD) 34
BARI (Chakwal) 23
Tarnab (Peshawar)
NARC, Islamabad
16
12

Genotypes Available at Different Inst.
Islamabad
Name of
Station
Mandarin&
Tangerine
Sweet
Oranges
Grapefruit Lemon&
Limes
Rootstocks Hybrids Fortunella
HRS, Sahiwal 24 46 16 26 46 10 2
UAF,
Faisalaba
d
9 30 10 9 24 5 2
ZTBL Farm,
Islamabad
21 28 8 23 - - -
FSC, Peshawar 6 20 5 4 11 - -
ORI, Sargodha 5 31 2 3 2 - 2
AARI,
Faisalaba
d
5 13 - 7 - 9 -
BARI, Chakwal 7 9 4 3 - -
TARS, Pehawar 4 8 - 3 1 - -
NARC, 2 4 - 3 3 - -

Citrus Gene Pool of Pakistan
Sweet Oranges
1. Atwood Early Navel 2. Ruby Blood
3. Olinda Valencia 4. Mediterranean
5. Boquet-De-Fleura 6. Pineapple
7. Hamlin 8. Moro Blood
9. Frost Valencia 10. Campbell Valencia
11.Torocco 12. Chinotto
13.Casa Grande 14. Marrs Early
15.Cutter Valencia 16. Salustiana
17.Kozan 18. Trabulus
19.Frost Navel 20. Hinkley
21.Joppa 22. Parson Brown
23.Sanguinello 24. Shamoute
25.Jaffa 26. Washington Navel
27.Musambi 28. Succari
29.Washington Navel-3033 30. Washington Navel-315

31. Sanguinello Mos. 4955 32. Tarocco Nuc.
33. Moro Nucellar 34. Navelate Orange
35. New Hall Orange 36. Navelina Orange
37. Valencia Late 38. Blood Red
39. Ruby Red Seedling 40. Midsweet Seedling
41. Amber Sweet Seedling 42. Valencia Seedling
43. Navel Seedling 44. Cara Cara Navel
45. Siamese Sweet Orange 46. Rhode Red Valencia
47. Venille 48. Sweet Seville
49. Lue-Gim-Roi-King 50. Mars Early
51. Dweet 52. Frost Navel
53. 7.U.A.F 54. 8.U.A.F

Mandarins
1. Kinnow 2. Willow Leaf
3. Wilking 4. Pixie
5. Ponkan 6. Murcott
7. Honey Mandarin 8. Sunket Sunkey
9. Nova 10. Oscila
11.Shamel 12. Clausellino
13.Satsuma 14. Clemenules
15.Clementine 16. Clementina
17.Fair Child 18. Freemont
19.Frost Dancy Tangerine 20. Algerian
21.Fortune 22. Sunbrust
23.Natal Nartjee 24. Mangal Singh
25.USDF Dancy 26. Kinnow Tetraploid
27.Kinnow Seedless 28. Feutrells Early

Grapefruit
Reed
Frost Marsh
Red Blush
2.
4.
6.
O. P
. Davis Seedling 8.
1.
3.
5.
7.
9. Ruby Red
11. Marsh Seedless
13. Rio Red
15. Frost Fresh
Shamber
Marsh Jbc-430
Red Mexican Foster
Little River
10. Foster
12. Star Ruby
14. Flame Seedling
16. Duncan

Hybrids
1. Seminola 2. Minneola Tangelo
3. Orlando Tangelo 4. Pearl
5. Mepo Tangelo 6. Kinnow (4x) X Kinnow (2x)
7. Kinnow (2x) X Kinnow (4x) 8. Succari (2x) X Kinnow (4x)
9. Kinnow (4x) X Succari (2x) 10. Mosambi X Kinnow
11. Kinnow X Mosambi 12. Feutrell’s Early X Valencia Late
13. Washington Navel X Duncan 14. Valencia Late X Duncan
15. Valencia Late X Jaffa 16. Jaffa X Valencia Late
17. Kinnow X Ferutrell’s Early 18. Ferutrell’s Early X Kinnow
19. Valencia Late X Feutrell’s Early 20. Mosambi X Shamber
21. Shamber X Mosambi 22. AARI Pride(PineappleX Mosambi)
23. Hamlin X Kinnow 24. Orlando X Kinnow
25. Fair Child X Kinnow 26. Kinnow X Orlando
27. Orlando X Fair Child

Lemon& Limes
Sweet Lime
1. Palestine 2. Peshawari Lime
3. Local Mitha
Acid Lime
4. Kaghzi Lime 5. Tahiti Lime
6. Eustis Lime 7. Lakeland
8. Bearss
Lemons
9. Allen Eureka 10. Corona Foothill Eureka
11. Prior Lisbon 12. Caver’s Lisbon
13. Cook Eureka-N 14. Frost Eureka-N
15. Limoneria 16. Foothill Lisbon
17. CaseCade Eureka 18. Frost Lisbon
19. Caver’s Lisbon O.L 20. Verna
21. Corpaci 22. Feminelo
23. Promofiori 24. Santa Teresa
25. U.C.L.A 26. Monachello
27. Mesero Lemon 28. Coock Eureka

Root Stocks
1. Rouh Lemon/Jatti Khatti 2. Citron/Mokari
3. Kharna Khatta 4. Khatta Taru Jabba
5. Sweet Lime 6. Jullundri Khatti
7. Jambheri Ceylon 8. Jambheri Lyallpur
9. Shaddock 10. Galgal
11. Dewana Khatti 12. Seville Kimb
13. Gada Dehi 14. Nasnaran
15. Sour Orange 16. Sylhet Lime
17. Mithi 18. Citrus Hystrix
19. Cleoptra 20. Mayer’s Lemon
21. Carrizo Citrange 22. Troyer Citrange
23. Savage Citrange 24. Citrumello-1452
25. Citrumello-4475 26. Sachton Citrumello
27. Milam 28. Red Rough Lemon
29. Keen Sour Orange 30. Brazillian Sour Orange

31. Bassie 32. Koethan Sweet Orange
33. Taiwanica 34. Rubidoux Trifoliate
35. Volkamariana 36. Yuzu
37. Macrophylla 38. Calpi
39. Pomercy 40. Bearss
41. Rangpur Lime 42. Etrog-6013
43. Etrog-861 44. Bitter Sweet Orange
45. Yuma Citrange 46. Sun Chu Shah
47. Smooth Flat Seville 48. Citrus Obvoid
49. Rangpur limeX Troyer Citrange 50. Benton Citrange
51. Trifoliate Orange 52. Sunki X Benecke
53. Algerian 54. Hirodo Bunton Pummello
55. Flying Dragon 56. Bigrade Australian
Kumquats
2. Mewa
1. Nagmi
Others
1. Bara Masi 2. Bunton Pummello

Establishment of Modern citrus Nursery

Common Nursery Management
Practices
• No scientific/technical basis
• No phytosanitory measures
• Selection of low quality seed, rootstock, bud
wood (Not certified)
• Problem of to have a true to type plant
• No disinfection of tools
• Budding/grafting at low height

• Proper site selection (No one is taking care)
• Lack of growing Structures
• Suitability and propagation methods are the
other problems
• Faulty cultural practices
• Unregistered nurseries
• Lack of indexing facilities

Citrus Certification Programme
• A virus-Free citrus bud wood program for Texas in 1948 (Roistacher
and Graca 1996).
• Certification of citrus in Turkey in 1950 (Balogu 1998)
• Certification and registration program in Florida in 1953 (Youtsey
1992)
• Virus and virus-like diseases of citrus in Greece and certification in
1970 (Kyriakopoulou 1998).
• The citrus bud wood improvement program for Argentina in 1992
(Anderson 2001)

• National program for the production of certified citrus
plants in Tunisia in 1993 (Cherifmattson 1998)
• Texas virus-free citrus bud wood program development
in 1993 (Kahlke et al 2000)
• Sanitary status and certification of citrus in Egypt in
1998 (Abdel-Salam 1998)
• In Pakistan certification program was started in 2001 at
U.A.F.

Detection
• Biological indexing (Mexican lime in the green
house at 18oC - 25oC )
• Lab. indexing (ELISA, PCR, Electron
Microscopy)

Virus Indexing
• Indicator Host
• Graft Inoculations
• Symptomology
• Greenhouse Requirements
• Serology and Molecular detection methods

Multiplication
• Foundation Trees (Indoor/outdoor)
• Seed Orchards (indoor/outdoor)
• Budwood increase (Preferred as a shadehouse
operation)
• Distribution/marketing of budwood
• Follow-up action by certification agency

Disease Free Nursery System
Followings are the main steps keeping in view the
successful establishment of certification model (Su,
1998):
• Micrografting for obtaining pathogen free citrus
foundation stocks.
• Scion- Propagation Parent Trees.
• Pathogen-free Citrus Seedlings.
• Citrus Growers.

FLOW CHART OF CITRUS BUDWOOD CERTIFICATION PROGRAMME
OVERSEAS IMPORTS
LOCAL SELECTIONS
BREEDING PROGRAMME
CANDIDATETREES
THERMOHERAPY
32C0
SHOOT TIP GRAFTING
INDEXING
SOURCE TREE GREEN HOUSE
FOUNDATIONBLOCK
INDEXAND ANNUALINSPECTION HORTICULTURAL EVALUATION
BUD & SEED
MULTIPLICATION
COMMERCIAL NURSERIES
CERTRIFIEDTREES
COMMERCIAL PLANTINGS

Activities in Certification Program
• Survey for the incidence of CTV (Punjab, Khyber.
PK, Sindh and Baluchistan)
• Lab indexing followed by biological indexing
• Grafting of citrus plant from virus free budwood
• Establishment of foundation block
• Production of virus free plants through shoot tip
grafting
• Production of disease free (nematodes) through
container grown citrus nursery.
• Marketing of virus free budwood and plants for
the nurserymen

Future Strategies
• Quarantine
• Certification
• (Establishment of sanitated citrus germplasm)

Suggestions
• Legislation in nursery industry should be made
• Govt. and private sector should be involved for
raising the certified plants on commercial level
• To make the disease free true to type progeny
plants, testing training should be extended from
government institutions
• Only certified plants should be recommended for
plantation and restrictions should be done for
such nurseries those do not follow it
• Quarantine measures should be observed strictly
• Enhancement and conservation of existed
Germplasm on more scientific basis

Citrus
Not Native
Typically Grafted
Long Harvest Season
Easy

Oranges

Navel Orange
October - January
3 - 3/12
0 - 6 Seeds
Small Crops

‘Cara Cara’ Navel
October - January
3 - 3 1/2
0 - 6 Seeds
Red Colored Flesh
Compact Growth
Habit

‘Hamlin’
October - January
2 3/4 - 3
0 - 6 Seeds
Most productive
Poor juice color

‘Valencia’
March - June
2 3/4 - 3
0 - 6 Seeds
Best Juice Orange
Excellent juice color

Grapefruit

‘Duncan’ Grapefruit
Dec. - May
3 1/2 - 5
30 - 70 seeds
Good Flavor
White Flesh

‘Marsh’
November - May
3 1/2 - 4 1/2
0 - 6 Seeds
Number 1 for
processing

‘Thompson’ (Pink Marsh)
December -May
3 3/4 - 4 1/2
0 - 6 Seeds
No blush to peel

Red Grapefruit
December - May

Tangerines and Hybrids

‘Minneola’
December -
February
3 - 3 1/2
7 - 12 seeds
Very Cold Hardy
Prominent neck at
stem end

‘Sunburst’
November -
December
2 1/2 - 3
1 - 20 seeds
Most widely planted

‘Murcott’ (Honey Tangerine)
January - March
2 3/4
10 - 20 seeds
Thin Skin
High sugar content

‘Temple’
January - March
2 3/4 - 3
15 - 20 seeds
peels easily
Pebbly rind texture
Cold sensitive

Satsuma
Sept. - November
2 1/4 - 2 1/2
0 - 6 seeds
Earliest of mandarin
types
Cold hardy
Loose skin

Acid Fruit

Persian Lime
June - September
1 3/4 - 2 1/2
0 - 1 seed
Thorny Trees
Cold sensitive
Susceptible to styler
end rot

Key Lime
Everbearing
1 1/4 - 1 3/4
3 - 8 seeds
Cold susceptible
Thorny or thornless

‘Meyer’ Lemon
November - March
2 1/2 - 3
10 seeds
Bush growth habit
Most cold hardy
lemon
Smooth skin
High juice content

‘Nagami’ Kumquat
Nov. - April
1 1/2 X 1
0 - 3 seeds
Very cold hardy
More acid than
meiwa

‘Meiwa’ Kumquat
Nov. - April
1 - 1 1/2
3 - 5 seeds
Large round
kumquat
Spicy, sweet pulp
Cold hardy

‘Tavares’ Limequat
November - March
1 3/4- 2 X 1 1/4 - 1
1/2
2 - 5 seeds
Good substitute for
limes
Cold hardy

Calamondin
Harvest all year
1 - 1 ½”
3 - 5 seeds
Great for containers
Flavors drinks,
marmalades and
jellies
Cold hardy