breeding for maize crops

1. Place of Origin: Mexico.
Origin of Cultivated Maize:
The genus Zea was previously considered as monotypic.
Later on teosinte has been included Euchlaena mexicana
has been changed as Zea Mexicana.
Another wild relative is Tripsacum (gamma grass). All the
three are inter crossable.
Maize
Zea mays (2n = 20)

2. Three Views About Origin
1.From Teosinte it arose. Teosinte is having cob
and tassel and easily crossable. This theory
was not accepted based on cytological
studies.
2.Maize arose from pod corn Zea mays var.
tunicata through natural mutation. This view
is the most accepted one. But origin of pod
corn is not known.
3.All the three came from common ancestor but
this common ancestor lost during evolution.

3. Ideal Plant Type in Maize
i. Plant with up right leaves which will increase
photosynthesis.
ii. Extended grain filling period to have uniform
well matured grains.
iii. Cob with increased row no. > 15.
iv. Multi cob plant
Floral Biology
The inflorescence is unisexual and monoecious.
Staminate (male)inflorescence is terminal are
known as tassel.
pistilate (female) is axillary are called as cob.

5. Tassel
It is a terminal lax panicle with spikelets arranged in rows in central axis and
lateral branches. Spikelets occur in pairs. One is pedicelled and the other sessile
but identical; the glumes G1, and G2 are long and membranous; with in the glumes
there are two florets, both staminate. The florets posses lemma and palea and two
fleshy lodicules, stamens are three in number, versatile, and pistil is rudimentary.
Cob
Maize is an example for protoandry. Pollen shedding begins three days before the
silk emerge from the cob. It is estimated that normal plant produces 2,50,00,000
pollen grains. Under normal conditions pollen is viable for 12-18 hours. Fertilization
occurs within 12-18 hours after the silk have been pollinated. The entire silk is
receptive.

6. Breeding Objectives
1.Yield
Complex character controlled by polygenes. Attention is to be paid to have ideal
plant type. Varietial hybridization as a maize breeding method did not gain
popularity. The main reason for this is difficulty in getting superior segregants.
2. Breeding for Pest and Disease Resistance
Shoot fly, Stem borer, Heliothis are major pests. Mexican varieties are resistant.
Downy mildews, leaf blight and helminthosporium are major diseases. Co1, CoH2
are resistant. Taiwan lines are resistant to downy mildew.
3. Breeding for High Protein
Composed of two fractions.
a) Protein in endosperm known as Zein which is nutritionally not balanced since
it is lesser in lysine and tryptophan. 80% protein found in endosperm.
b) Protein in germ (embryo) 20% balanced one. By increasing the embryo size we
can increase protein content.

7. 4. Breeding for Increased Oil Content
12–15% in germ.(By increasing the embryo size we can increase oil content.)
5. Alternate Sources of Cytoplasm
CMS - T. susceptible to Helminthosporium, C and S Resistant.
6. High Yielding Baby Corn
Z.mays. var. sachharata, Sweet corn. The green cobs can be eaten as salad.
The cobs can be harvested 45 days after sowing. CoBc 1 is latest variety of baby
corn.

8. Breeding Methods
1.Introduction
Initially the varieties were all introduced one. Sikkim primitive
1.Sikkim primitive 2. Mexican line
2.Mass Selection
Prior to 1945 mass selection was the only method used for maize improvement.
KT 1 - U. P. RAS 1 - Rajasthan. By adopting mass selection technique it is
possible to get yield increase by 19% per cycle.
3. Ear to Row Selection
This method involves selection of a number of phenotypically desirable ears out
of a population grown in isolation. The selected cobs are harvested on single
plant basis and keeping part of the seeds & remaining sown in rows. Based on
the best performing rows during next season the reserve seeds are sown.
This method is suitable for characters having high heritability like oil content
and protein content. But it was not helpful to get increased yield.

9. 4.Modified Ear to Row Method
Proposed by Lonquist
i) Best ear heads from population selected (100 No.) and harvested on single
plant basis and threshed individually.
ii) The single heads harvested are raised in progeny rows in more than one
location representing different environment with local checks.
iii) In the main station the progeny rows are used as crossing block. Pollen
from best plants are collected, mixed and used for crossing the rows.
Select best five plants from each rows and harvest them separately record the
yield. On the basis of performance of over all locations only top 20% progenies
are selected. These 20% will include the five plants selected.
iv) The seeds from 5 plants selected are sown in progeny rows and cycle is
repeated.
5. Hybridization and Selection
Not popular since isolation of superior recombinants was not made.

10. 6. Heterosis Breeding
Instead of using CGMS lines, detasseling the female inbred line is followed in
India.
Crossing the inbreds of indigenous x exotic origin resulted in release of best
hybrids.
Indian × Indian - 24 to 43% yield increase.
Indian × U.S. dent 58 %
Indian dent × Caribbean Flint 47 to 54 %
i.Single cross hybrid - CoH 1, CoH 2.
ii.Three way cross hybrids - Ganga -5
iii .Double cross hybrids - CoH 3
iv. Double top crop hybrid - White kernel hybrids - Ganga safed 2, Histarch,
Ganga 4.
7. Population Improvement
Recurrent selection technique was initiated by Dhawan in 1963. The initial
synthesis of composites were done from high yielding inter varietal crosses
which exhibited minimum inbreeding depression.
Kisan, Jawahar, Vikram, Sona, Vijay, Amber.Co 1 K. 1

11. Tool Employed for Seed Production
In maize, hybrid seed production is achieved through detasseling, which is the
physical removal of male part from the female plants and thereby allowing the
plant to act as female which is in turn crossed with selected male plant and
effect seed setting. This is possible in maize alone due to the monoecious and
protandry nature of the flowers.
Types of Hybrids
In maize, single, double and three way cross hybrids are available.
(i) Single Cross Hybrid: It is the cross between 2 inbreds, where one
serve as female and other as male.
(e.g.) COH1 : UMI 29 × UMI 51
COH2 : UMI 810 × UMI 90
(ii) Three way cross Hybrid: It is the cross between a single cross hybrid
(A×B) which serve as female with another inbred (C) which serve as male parent.
(e.g.) Ganga 5 : (CM 202 × CM 111) × CM 500
(iii) Double Cross Hybrid: It is a cross between 2 single crosses (A×B) and
(C×D) involving 4 inbreds (A,B,C,D) (e.g.). Deccan hybrid -(CM 104 × CM 105) ×
(CM 202 × CM 201) COH3 -(UMI 101 × UMI 130) × (UMI 90 × UMI 285)

12. Steps in Hybrid Seed Production
Seed Production Stages
Class of Seed
Breeder seed Foundation seed Cirtified seed
1.Varieties/Inbreds
A A+ A++
(Multiplied at Different Stages)
2.Single Cross Hybrid
A, B A, B AXB
(A and B Multiplied Separately under Isolation)
3.Three ways Cross Hybrid
A, B, C AxB, C (AxB)xC
4. Double Cross Hybrid
A, B,C, D (AXB), (CXD) (AXB)X(CXD)

13. Detasselling
The tool employed in hybrid seed production of maize is known as detasselling. Tassel is the
male inflorescence of maize. Detasselling is removal of tassel/male flowers from the plant.
Detasselling should be done in the female parent of hybrid alone. It should be removed before
anthesis and immediately after emergence. Detasselling should be completed when the tassel
is well out of the boot leaf but before the anthers shed the pollen. It is done everyday from
anthesis, upto 14 days.

15. THANK YOU
SO MUCH…….