Alternate bearing causal factors and remedial measures in Citrus

1. Alternate Bearing in Citrus
Presenter
Ashmita Bajagain
HRT-04M-2018
M.Sc. Ag. (Horticulture)
Department of Horticulture
Rampur, Chitwan

2. Outline of Presentation
 Introduction
 Rationale of the study
 Objectives
 Methodology
 Results and discussion
 Conclusion

3. Introduction
 Citrus is the most important evergreen fruit crop
 Citrus one of the major fruits of Nepal
 Climatic range of 800-1400 masl is favorable
 Cultivated in 62 districts of Nepal with 8.79 mt/ha
(MoAD, 2017)
 Alternate bearing is one of the major problem
 It is different from irregular/periodicity of cropping
(Verreynne, 2009)

4. Rationale of the study
 Many marketing problems associated with
alternate bearing (Verreynne, 2009)
 Orchard management is very problematic
(American Society for Horticultural Science, 2009)
 Fluctuation of price arises which is undesirable to
growers (Adouli et al., 2018)
 Compromises on quality and consistency of
production (Stander, Berry, & Cronj, 2018a)
 Not quantitatively measured in Nepalese orchard

5. Objectives
 To know about factors causing alternate bearing
in citrus
 To study about remedial measures of alternate
bearing in citrus

6. Methodology
 To fulfill requirement of term paper for internal
assessment
 Various books, journal articles and research
papers were consulted
 Information collected is mentioned on results
section
 Referencing was done in APA style (6th edition)

7. Results and Discussion
 Alternate Bearing in Fruit trees
 Alternate Bearing in Citrus
 Causes of alternate bearing
 Control of alternate bearing

8. Alternate bearing in fruit trees
 Process by which cycles of heavy yield (on
crop) one year are followed by a light yield (off
crop) the next (Singh, 2005)
 Prominent in Anacardiaceae (Mango,
Pistachionut), Carlyaceae (Hazelnut), Oleaceae
(Olives), Rosaceae (Apple, Pear, Plum, Apricot),
Rutaceae (Orange, Tangor, Satsuma), tamarind
and jamun (Sharma et al., 2017)

9. Alternate bearing in Citrus
 Synchronized tendency of a shoot, branch, or tree
to flower profusely and produce an excessive
number of fruit in one season followed by a few
flowers and fruit in the following season (Stander,
Barry, & Cronj, 2018b)
 Fruit-induced inhibition of flowering is the primary
cause of alternate bearing (Martinez-Alcantara et
al., 2015)

10. Causes of alternate bearing
1.Environmental factors
 Extreme environmental
condition caused an immediate
strong alternation for the whole
orchard and it tend to continue
the cycle (Lavee, 1989)
Fig. Alternate bearing in half of
a tree initiated originally by
wind on the right side of the
tree, causing abscission of
flowers and fruitlets(Verreynne,

11. Endogenous factors
Alternate
Bearing
High level of
ABA and t-
ABA arrest the
bud growth
GA3 synthesized by
developing embryo
inhibits shoot
emergence flower
fruit induction near
fruits
Roots- source of
cytokinin synthesis
Vegetative growing
points- strongest
sink
Limitation of
cytokinin will
result in lower
flower bud
development

12. Carbohydrate effect
On year
• Fruit overload
• (CHOH)n stress
• Mineral deficiencies
• Hormonal imbalance
Inhibition of
FBD
Creates off
year
• Repair and
recovery
On year
Fruit load
•Spring flush, floral development, anthesis, fruit set
demand large energy that cannot be furnished by current
photosynthesis and must be obtained from tree reserves
(Butsan & Goldschmidt, 1998)

13. Cultivar and age of tree
 Range of susceptibility to AB; Mandarin >
Pineapple, Grapefruit> Valencia and Hamlin >
Navel cultivars; Seedy varieties > Seedless varieties
( Verreynne, 2009; Wheaton,1989)
 Alternation is stronger with easy-peeling cultivars,
early and maturing cultivars to late maturing
 Young trees with normally high vegetative vigor
shows low alternation than the old trees (Verreynne,
2009)

14. Crop load
Fig. Effect of fruit on the return bloom (Verreynne, 2009)
•The presence of a large number of fruit appears to have
negative correlation with floral shoot production as well as
vegetative growth and also alters source-sink relationship
(Martinez-Alcantara et al., 2015; Moss, 1971)

15. Late harvest
 Length of the time the crop
remains on the tree after
maturity increases the
degree of alternate bearing
Fig. Flush growth (g) and carbon
consumed by fruit (g) in ‘Moncada’
mandarin. The nonlinear regression
is significant at p ≤ 0.05 (Martinez-
Alcantara et al., 2015)
(Verreynne, 2009)

16. Rootstock
Rootstock
Photosynthates
translocated
into roots parts
If supply is
less,
reduces
feeder roots
•Tree vigor induced by rootstocks is not related to
alternate bearing, as vigorous stocks like Rangpur
lime have similar alternate bearing characteristics to
size-limiting stocks like trifoliate orange (El-Zeftawi
& Thornton, 1975)

17. Control Measures
1.Fruit thinning
2.Use of growth retardant
3.Girdling of branch
4.Reducing crop influence by early harvest
5.Pruning

18. Fruit thinning
 Hand and chemical
thinning are in practice to
achieve this objective
(Wheaton, 1989)
 In Japan by thinning
larger fruit was obtained
in the same year and more
number of flowers and
yields in the subsequent
year (Mazhar et al., 2007)
Purpose of
fruit thinning
Increases leaf
fruit ratio (20-40
leaves required
per fruit)
Remaining fruits
become larger
Reduce crop load
(Westwood, 1988)

19. Use of growth retardant
 Effectiveness of PBZ in promoting flowering in
Citrus depends on the fruit load (Martinez-
Fuentes et al., 2013)
 Chemicals effective on grapefruit:
Chemicals Dose
Triiodobenzoic acid 500 mg/ltr
Benzothiazol-2-oxyacetate (BTOA) 50 mg/ltr
Trimethyl ammonium chloride (CCC) 100 mg/ltr
(Kessler et al., 1977)

20. Fig. Effect of paclobutrazol (PBZ 1 g tree−1) and
gibberellic acid (GA3 50 mg l−1) applied in floral
bud inductive period (November 25) on flowering
intensity of 'Hernandina' Clementine mandarin

21. Girdling of branch
 Girdling is known to cause accumulation of
Carbohydrates within the girdled branch
 Girdling and fruit removal dramatically increased
flower production in ‘Murcott’ (Goldschmidt, 1999)
 Girdling in October of small or large fruitless
branches increased 2-3 folds both starch content of
leaves and flower number (Goldschmidt et al., 1985)

22. Table: Effects of girdling on starch and flowering of
fruitless branches of different sizes of 'Murcott' mandarin
(Girdling on 26 October, sampling after 1 month)
Branch size Girdled
Leaves starch Flowers (10 April)
mg/g Ratio Number Ratio
Small + 159.0 a 3.7 70 c 2.8
Small _ 42.7 b 25 d
Large + 153.7 a 2.8 810 a 2.9
Large _ 54.9 b 280 b
(Goldschmidt et al., 1985)

23. Early harvest
 Fruits that may be kept on the tree for months after
they have attained ripeness can be harvested early
(Monselise & Goldschmidt, 2015)
 Since, late hanging of fruit to meet color or internal
fruit quality standards increases the severity of
alternate bearing (Verreynne, 2009)
 Early harvest is of prime importance

24. Pruning
 Pruning or mechanical removal of fruit is the most
common method of reducing crop load
 Scheduling topping and hedging can reduce the crop
load during the heavy crop years is beneficial
 It's advantageous to be done if crop loads can be
estimated (Mazhar et al., 2007)
 It acts by modifying the distribution of
carbohydrates between shoot elongation and flower
differentiation (Gomathinayagam et al., 2007)

25. Conclusion
 Number of fruit on a tree is the main factor influencing
the floral intensity of the return bloom
 Major components are gibberellins and carbohydrates,
however, other components involvement also cannot be
excluded
 Carbohydrates concentration should be maintained in tree
so that source-sink relation can always be maintained
 Balance between vegetative and reproductive growth to
ensure moderate crop year after year

26. THANK YOU