1. Inbred lines are developed through repeated self-pollination or inbreeding of plants over multiple generations to produce genotypes that are homozygous and genetically uniform. 2. The pedigree method is most commonly used to develop maize inbred lines, involving self-pollination over 6-7 generations with selection of desirable plants each generation. 3. Doubled haploid lines can also be used, in which haploid cells are induced and then chromosome doubled to instantly produce completely homozygous lines.

1. Breeding Methods in cross pollinated
crops:
Inbred Line Development
Dr. NAVEENKUMAR K.L
Assistant Professor
Dept. of GPB
UAHS Shivamogga

4.  Single cross: when two inbreds , say A & B, are crossed the
hybrid/ F1 (A x B) is known as single cross hybrid.
 When two single crosses, say A x B & CXD, are crossed the
resulting hybrid population, (A x B) X (CXD) is known as
double cross hybrid.

6. What is inbred line?
In allogamous species, a true breeding line obtained by
continuous inbreeding/selfing is called inbred line.
or
Inbred lines are homozygous genotypes produced by
repeated selfing with selection over several generations.
 An inbred line consists of individuals with the same
genotype.
 It is developed and maintained by repeated selfing of
selected plants.

7.  Inbred lines are developed from a variable source
population.
 The source population is generally an open-pollinated
variety (First cycle inbreds) or it may be synthetic, a
single cross or a double cross (Second, third or fourth
cycle inbreds).
 Inbreds are usually developed through a suitable
system of close inbreeding (6-7 generation of selfing).

8. Main features of inbred line are given below:
1. It is relevant to cross pollinated species
2. It is true breeding
3. It is homozygous and homogeneous

9. Inbred Line Development in Cross Pollinated Crops
 The pedigree method of breeding is the most widely used
method to develop inbred lines & it is referred to as “standard
method” when an open pollinated population is sampled.
 After each selfing desirable plants are selected and self
pollinated or sib pollinated.
 Usually it takes 6-7 generations to attain near homozygosity.
 The purpose of inbreeding is to fix the desirable characters in
homozygous condition in order to maintain them without any
genetic change.
 Inbred lines are developed for the production of Hybrid
seeds.

10. There are three operations involved in the
production of hybrid varieties-
1. Development of inbred lines
2. Evaluation of inbreds
3. Production of hybrid seed

11. Development of inbred lines
There are two methods of developing inbred lines-
1. Selfing of heterozygous populations
(Pedigree method, Bulk method, Single seed
descent method, Back cross method)
2. Doubling of haploids

12.  Pedigree method is generally practiced in the
development of inbreds.
PROCEDURE
Development of inbred lines:

15. 15
Strategies for the development of inbred lines
Director of Maize Research 2010

16. 16
A×B C×D G×H
F3 ID advanced
Y
X×Y
Select productive
hybrids
F4 to F7
F2 Inbreeding
depression study
Evaluation in combination
breeding biotic and Abiotic
stresses
X
Categorisation
seed
Pollen parent
Maize scheme UAS Dharwad
Multiple parent inbred development

17. Doubled Haploid (DH) lines – What are they?
 Haploid: an individuals with the gametic
chromosome number (n) in its somatic cells.
 A Doubled Haploid: is a genotype formed when
haploid cells (n), i.e. egg or sperm cell undergo
chromosome doubling (2n).
 The resulting individual is completely homozygous.
DOUBLED HAPLOID LINES IN HYBRID BREEDING

19. DOUBLED HAPLOID LINES IN HYBRID BREEDING
19
 First Haploid maize - Stadler and Randolph (1929)
 Spontaneous haploid induction rate in maize of 0.1%
and suggested that haploids could be used for line
development in hybrid breeding Chase (1947, 1951)
 COE (1959) - 2.3%, crosses with inbred line stock6.
Lashermes and Beckert (1988)- WS14 (W23ig X Stock6)
Geiger and Gordillo, 2009 - inducing lines display high
induction rates of 8 -10% .

20. 20
Maize Genetics Cooperation 2010
Stock 6 MHI PHI-1
PHI-2
PHI-3
PHI-4
12.8
14.5
13.0
12.1
7.2
1.2
PHI – Procera Haploid Inducer

21. 21
Haploid identification method
Haploid embryos can be selected based on
morphological and physiological markers
Identification marker is the ‘red crown’ or
‘navajo’ kernel trait encoded by the
dominant mutant allele R1-nj of the ‘red
color’ gene R1 Geiger and Gordillo,
2009
kernels with a haploid embryo have a
significantly lower oil concentration than
those with a diploid F1 embryo
Rotarenko et al (2007),

22. 22
CIMMYT

28. Achievements
 In India inbred lines are developed and released
through co-ordinate maize improvement scheme
and are designated as CM (Co-ordinate maize),
 CS (Co-ordinate sorghum)
 CM-100-199 - Yellow flint
 CM-200-299 - Yellow Dent
 CM-300-399 - White Flint
 CM-400-499 - White Dent
 CM-500-599 - Yellow
 CM-600-699 - White 2

29.  In India, Hybrid varieties were first to exploit heterosis in
maize.
 The first hybrid varieties in maize were released in 1961, when
four double cross hybrids, viz., Ganga1, Ganga101, Ranjit &
Deccan, were released for cultivation.
 In sorghum, first hybrid CSH1 was released in 1964.
 In pearl millet, first hybrid HB1 was released in 1964.
 Castor- GCH3 (1968)
 Cotton - H4 (1970)
 Sunflower- BSH1 (1980)
 Pigeon pea - ICPH-8 (1991)
 Rapeseed - PGSH51 (1994)
 Rice -PRH10 (2001)
 Tobacco- GTH1 (1996) were first released hybrid varieties