A presentation on the production technology of Citrus fruits

1. Presentation

2. Submitted to:
Dr Muhammad Nafees
Submitted by:
Mohsin Ashfaq
Roll no:
C007
Subject:
Horti-402
UCA&ES

4. Swingle (1943) divided the genus Citrus into three
independent genera: Citrus, Poncirus, and Fortunella.
He put 16 species under Citrus, four under Fortunella,
and only one species under Poncirus. Hodgson (1961)
divided Citrus into 36 species. Swingle’s classification
is usually followed, with some modifications as
suggested by Hodgson.
 All three genera belong to the sub—family
Aurantioideae of the family Rutaceae. The sub—family
consists of two tribes, Clausenae and Citreae4 Citreae
has 33 genera including Citrus, Poncirus, and
Fortunella.

5.  Seeds are produced in the
plant kingdom, generally, as
a result of pollination. Many
of the commercial species in
the citrus genus, are self-
fertile, meaning that the
pollination of a pistil
(female flower part) may
occur by pollen from
stamens (male flower part)
on the same
plant.Additionally, most
citrus varieties express
some level of parthenocarpy.
Parthenocarpy is the ability
of plants to develop fruit
without pollination
 (which means no or very few
seeds if trees with fertile
pollen are not located
nearby). Most varieties of
navel oranges, such as Parent
Washington, Frost Nucellar,
Atwood, Fisher, Bonanza or
Lane Late, produce mostly
parthenocarpic fruit. These
navels rarely produce seeds
because they are male sterile
(i.e. they produce no pollen)
and even if pollinated the
mother cells will tend to
abort. Occasionally a seed
may develop but the seed is
usually produced asexually.

6.  Pollination of fruit trees
is required to produce
seeds with surrounding
fruit. It is the process of
moving pollen from the
anther to the stigma,
either in the same flower
or in another flower.
Some tree species,
including many fruit
trees, do not produce
fruit from self-
pollination, so pollinizer
trees are planted in
orchards.
 The pollination process requires a
carrier for the pollen, which can be
animal, wind, or human
intervention (by hand-pollination
or by using a pollen sprayer). Cross
pollination produces seeds with a
different genetic makeup from the
parent plants; such seeds may be
created deliberately as part of a
selective breeding program for
fruit trees with desired attributes.
Trees that are cross-pollinated or
pollinated via an insect pollinator
produce more fruit than trees with
flowers that just self-pollinate.[1]
In fruit trees, bees are an essential
part of the pollination process for
the formation of fruit.[2]

8.  family Rutaceae
 subfamily Aurantioideae
 tribe Citreae
genus Citrus (sweet orange,
mandarin, grapefruit, lime, and lemon)
 Fortunella (kumquat)
 Poncirus (trifoliate orange)

9. GENUS PONCIRUS.
 . The genus Poncirus has
only one species, P.
trifoliate Raf., which has
compound leaves with
three leaflets and is
deciduous. The tree is
small and spiny
THE GENUS FORTUNELLA
 has four species, of which
the commercially
important ones are F.
margarita Swing. (oval
kumquat) and F. japonica
Swing. (round kumquat).

10.  Citrus cultivars are grown in varying quantities in
countries with tropical or subtropical climates.
Cultivation in each country is determined by the
minimum temperature occurring in the region, the
temperature tolerance of the specific cultivar,
latitude, altitude, proximity to large bodies of water,
ocean currents, air drainage, and local conditions.
Citrus stands first in area and production among the
world’s tree fruits. A world production target for
1990 was fixed at 17 million metric tons (MMT)
(Wardowski et al. 1986).

12.  CLIMATE
requirements.
 Citrus fruits are grown
in tropical and
subtropical climates. In
these regions citrus
groves are found from
sea level to 45O75O m
elevation. In Pakistan,
the central divisions of
Punjab -‘--- Sargodha,
Faisalabad, Lahore, and
Multan produce
excellent citrus. In
NWFP, Peshawar, DI.
Khan, and Dir are
important citrus—
producing areas
 Raising of rootstocks
 Most citrus seeds are polyembryonic and
produce seedlings true to type. Citrus
rootstock species are therefore propagated
through seeds in the nursery. The fruit for
seed extraction is taken from healthy,
vigorous trees by the first week of September.
The fruit is cut into halves and twisted to
squeeze out the contents. The seeds are then
separated from the pulp and juice and
washed to remove the gelatinous material.
They are dried by placing them in partial
shade. It is best to grow the seeds fresh as
they cannot be stored for long. Seeds stored
in charcoal under dry storage condit ions lose
nearly 50% of their viability after 45 days,
therefore storage of rootstock seeds is not
generally advisable; but if it is necessary to
ship them far, storage in ground charcoal or
packed in vacuum tins at a temperature of
3—10°C is recommended.
 Seeds are sown either in September or in
February—March

13.  . Citrus trees are evergreen and need appropriate
irrigation all year round. Successful citrus culture thus
requires a permanent source of water. However,
over—irrigation is generally more harmful for citrus
fruits than under-irrigation, and this principle should
guide the irrigation schedule for citrus orchards. The
frequency and amount of irrigation depend upon
climatic conditions, soil type, kind and age of trees,
number of trees per hec tare, and rootstock used.
Citrus orchards should be given restricted watering
during winter, with one heavy irrigation about two
weeks before blooming

14.  Hydrogen, oxygen, and carbon are
available from water and air, while
the other 13 are mainly absorbed by
the roots from the soil. Among the
major elements absorbed from the
soil are nitrogen, phosphorus,
potassium, magnesium, and calcium.
N, P, and K are repeatedly applied in
the form of fertilizer, while the rest
are taken up from the soil resources.
If such soil conditions cannot be
corrected, foliar sprays of these
elements are used. Foliar spray,
particue laxly of trace elements like
zinc, manganese, iron, copper, and
boron is frequently applied to
orchard trees grown in alkaline soil
conditions to overcome the effects of
malnutrition.
 Early experiments conducted on
sweet oranges and grapefruit in the
Punjab had found that continuous
use of chemical nitrogenous
fertilizers like amrnonium sulphate
and sodium nitrate enhanced yield
over control but also induced
mottling. This situation was
remedied by the addition of FYM
 A common finding of all these
experiments is that the use of FYM as
a part of the fertilizer programme for
citrus is immensely important.
Besides increasing yield, it noticeably
im proves fruit quality. The results of
experiments on three—year—old
Valencia late orange budded on sour
orange stock at Peshawar (Said and
lnayatullah 1962) indicated a good
response to nitrogen and FYM, while
application of phosphorus and
potash alone did not affect the yield
of sweet oranges.

18.  Alternate bearing in
fruit trees is the habit of
bear- ing heavily in one
year called the on—year
and very little or not at all
in the second year called
the off—year. This
characteristic is
manifested by several
citrus cultivars like the
mandarins Kinnow and
Wilking, the sweet
oranges Valencia Late and
Washington Navel, and
Marsh seedless
grapefruit.
 Unfruitfulness . Sometimes
citrus cultivars do not
produce a commercial crop
for years. This situation may
be attributed to genetic or
physiological causes like
incompatibility, heterostyly,
and ovule abortion.
Physiological causes involve
hormonal or nutritional
imbalances which result in
general weakness or
excessive vegetative growth,
preventing the trees from
bloomihg and bearing fruit.

19. YOUNG FRUIT DROP
 Drop of young fruit occurs
in May- June. This is
another natural load—
shedding by the trees. This
drop consists of poorly
developing fruits or those
which cannot survive dry
conditions and high
temperatures. Under these
unfavorable conditions
embryo abortion occurs,
PRE-HARVEST DROP
 This drop of fruit is during
the mature stage and is of
great concern to growers. It
is a loss of full—grown fruit,
and therefore a lot of
research has been conducted
to overèome this problem.
The drop occurs when a
premature abscission layer
develops, which is presumed
to be due to the failure of
auxin synthesis within the
tree

22.  Citrus withertip. This
disease is caused by
Colletotrichum
gloeosporioi des. The
pathogen attacks all
the aerial parts of the
plant ‘— branches,
leaves, and fruit.
Withering of branches
from tip towards base
is the most
characteristic
symptom
 Citrus leaf miner This
is a small silvery-white
insect with black eyes
and wings fringed with
hairs. The larvae make
silvery-white galleries
on the young leaves and
tender shoots. Infested
leaves curl up and
finally wither and dry
up. Young nursery
plants suffer the most,
althougi full-grown
trees are not immune.