This document discusses hybrid seed production in Brassica napus (canola). It begins with an introduction to B. napus and heterosis. It then discusses the development of inbred lines, combining ability testing, inducing male sterility, hybrid seed production steps, selection criteria for hybrids, and maintaining hybrid purity. Key advantages of hybrids over open-pollinated varieties are also summarized, such as higher yield potential and better stress tolerance in hybrids. The document provides references for further reading on the topics covered.
4. Introduction
Brassica genus consists of approximately
100 species, including Brassica napus L.,
commonly known as oilseed rape. It is
originated in either the Mediterranean
area or Northern Europe. It is thought to
have originated from a cross from two
closely related diploid species, Brassica
oleracea and Brassica rapa.
(Jessop & Toelken 1986)
4
5. Conti…
An important phenomenon in biology, the
hybrids show better growth and fertility
over their parents (Darwin, 1876). Such
hybrid vigour or heterosis was
rediscovered nearly a century ago as an
amazing agricultural fact that has been
found to occur in many crop species
(Shull, 1908).
5
6. Conti……
Sprague and Tatum (1942) discovered the
concepts of general combining ability
(GCA) and specific combining ability
(SCA). General combining ability and
Specific combining ability are associated
to additive and non additive genetic
effects respectively (Rojas and Sprague,
1952).
6
7. Conti…
The importance of heterosis in agriculture
is clear from the impressive increases in
yield calculated follow the entry of hybrids
to crop production over past 50 years
(Duvick, 1999). Heterosis enhances crop
production by at least fifteen percent
which in combination with modern, higher
seed yielding (Fu, 2007).
7
8. Conti…..
Inbred lines and better agronomic
techniques have resulted in constant
increase in performance (Duvick, 2001).
Additive gene effects mainly contributed
to hybrid performance because the mean
squares of GCA were higher as compared
to SCA {Qian et al. (2007)}
8
10. 10
Hybrid Seed
“A seed developed after crossing two
selected homozygous pure lines (Self
pollinated crops) or inbred lines (Cross
pollinated crops)”.
11. 11
ROLE / IMPORTANCE OF HYBRIDS
High yield {Sincik et. al. (2011)}
Price stability
Extension in Canola oil availability
{Sing et. al. (2010)}
12. 12
Characteristics of Hybrid Seed
High yielded
Larger hybrid seed size boosts early vigor
for quicker ground cover {Turi et. al. (2011)}
Uniform maturity and excellent
standability makes harvest easier {Prat et
al. (2002)}
13. 13
Hybrid heterosis increases yield and oil
content to maximize profitability{Hu
(1999)}
Improved stress tolerance reduces the
seasonal variability
Unique hybridization system optimizes
hybrid seed quality
14. 14
Uses of Hybrid Seed
Used only to raise F1 crop
Not useful as F2 crop because of
segregation
Useful under high and precise input
system
15. 15
Breeding Objectives
High yield (Malek et al. (2012)
Earliness {Vaghela et. al. (2011)}
More Seed weight {Prat et al. (2002)}
More No. of seeds/pod
More No. of pods/plant
Disease/insect pest resistance
17. 17
Steps involved in Hybrid Breeding
Development of inbred lines
(07 Generations of selfing)
Combining ability testing{Grant, W. D.
Beversdorf. 1985}
Induction of male sterility and fertility
restoration systems in selected lines
(Pathania A. et al.
Hybrid seed production
18. 18
STEPS INVOLVED IN INBRED LINE
DEVELOPMENT
Selfing up to F7
e.g. Brassica napus (canola)
Controlled selfing
Identification of flower
Flower bagging
19. 19
STEPS INVOLVED IN COMBINING
ABILITY TESTING
No. of combinations: n (n – 1)/2
n : 12 (12 – 1)/2 = 66
(Only direct crosses are required)
Synthesis of F1 {Saha,. S. C. 2011}
Emasculation
Pollination
Evaluation of F1hybrids
20. 20
EXPLANATION OF SPECIFIC COMBING
ABILITY
Inbred line development {Etedali and
Khandan,2012}
Combining ability testing (Chapi et al. (2008))
Male sterility induction(Renard,M. et al. 1993)
Genetic
Cytoplasmic
Chemical e.g EMS,Mustred gas (Inhibition of
male flowers) (Sumie et al. 2003)
Manual
Emasculation
Clipping of male flowers
21. 21
SELECTION CRITERIA OF HYBRIDS
Indeterminate (Continuous
growth/tall)
Determinate (Dwarf)
Disease resistance
Insect pest resistance
26. 26
Pollination
Cross pollination requires pollen
movement from the male to the
female inbred plants.
Placement of bees in the field
during flowering assists pollen
flow to maximize cross pollination.
29. 29
Differences between hybrid and
open-pollinated Variety
Hybrid canola generally has a higher yield
potential(45 mon/acre) than in-bred OP
varieties(27 mon/acre). This improved yield is
achieved through a combination of superior
traits, such as larger seeds assisting with early
vigor and better stress tolerance.
The early vigor of hybrids provides competition
with weeds (Lakshmi et al. (2001) ).
Hybrids can produce more biomass, making them
a better choice for grazing when grown as a dual
purpose crop.
Seeds of hybrid is around two and a half times
more expensive than OP canola seed.
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