A,B,R line , hybrid production, plant breeding

1. A,B & R LINES DEVELOPMENT OF SELF AND
CROSS POLLINATED CROPS AND THEIR
MAINTENANCE BREEDING FOR HYBRID
SEED PRODUCTION

2. Lines defined as a group of genetically similar plants or Crops having
common parents or ancestors.
WHAT IS LINE DEVELOPEMENT ???
● Production or developement of particular type of desired lines.
● When we talk about development of lines in hybrid seed production then there
are three types of lines 1-A line
2-B line
3- R line
And two types of line system i.e. THREE LINE & TWO LINE SYSTEM

3. WHAT IS A, B & R LINES ???
A LINE
● Male sterile
● Use as
female
parent.
● Desired
characteristic
s
B LINE
● Maintainer
line
● Male fertile so
use as Male
parent
R LINE
● Restorer line
● Male fertile
● Desired
characteristic
s

4. WHAT IS THREE LINE
DEVELOPEMENT ???
● Based on CGMS
● A,B & R lines used
● Cytoplasm is main controller of sterility
● Nucleus contain R gene for restoration of fertility
● R: Male fertile ,r : inactive allele
● RR - Male fertility
● Rr- Male fertility
● rr- Favour cytoplasmic effects

5. CGMS SYSTEM : –
Male fertile Male fertile Male
fertile
Male fertile Male fertile Male sterile
● This is the case of cytoplasmic Male sterility
where dominant nuclear gene restores fertility.
● Discovered by Jones and Davis in 1944 in
onion.
● Now CGMS has been reported in several
Crops like onion , rice , maize ..etc.
● Cytoplasmic Male sterile line can be
maintained by crossing the Male sterile
cytoplasmic line with Male fertile cytoplasmic
line as given below..
(ms/ms) S × ( ms/ ms) F —----> (
ms/ms) S
Male sterile Male fertile Male
sterile

6. FUNCTION OF A , B & R LINE :-
Function of B lines:-
B line ( Male fertile) is use to maintain A line ( Male sterile/
female line)
Sterile
cytoplas
m
Sterile
cytoplasm
Characters of A line
similar with B line, so
progeny will be similar
A LINE B LINE
A LINE

7. MAINTENANCE OF A LINE IN FIELD:-
● A line is cross with B line
● Planting ratio should be 4 : 2 ( A : B )
A line (4)
B line ( 2)

8. HYBRID SEED PRODUCTION:-
Hybrid seed production using A & R lines
● A line cross with R line for hybrid ssed production ( F1 progeny)
● In hybrid seed production field the plantation ratio is 4 : 2 and seed must be collected from A line.
A line rows( 4 ) R
line rows (2)

9. THREE LINE SYSTEM AT A GLANCE…
A line B line
A line R line
Hybrid seed
( Male sterile) ( Male
fertile)
( Male sterile) (
Male fertile)
F 1 fertile hybrid seed

10. TWO LINE SYSTEM :
Why two line system ???
● Difficult to maintain CGMS system.
● Problems in maintenance of A line
● High seed production cost
Generally there are two approaches
1.Environment sensitive Male sterility ( EGMS)
2. Chemically induced Male sterility ( CIMS)

11. ENVIRONMENT SENSITIVE MALE STERILITY (
EGMS)
Types of EGMS
1.PGMS ( PHOTOPERIOD SENSITIVE GENETIC MALE STERILITY)
2. TGMS ( TEMPERATURE SENSITIVE GENETIC MALE STERILITY)
3. PTGMS ( PHOTOTHERMO SENSITIVE GENETIC MALE STERILITY)
Interaction between nuclear genes and environmental factors . It is more popularly termed
as Two line hybrid breeding as against Three line hybrid breeding in case of CMS system

12. PGMS ( PHOTOPERIOD SENSITIVE GENETIC MALE
STERILITY)
Use in temprate countries having large changes in day length, usually practised in paddy
Crops.
Conditions :
Less Than 13 hours photo periods leads to complete Male fertile plant , and more than 14 Hours photo
period leads to complete Male sterile plant.
Maintenance of PGMS line: Photo period Less than 13 hours
PGMS LINE ( Male fertile)
Selfing in isolation
PGMS LINE ( fertile)

13. Hybrid seed production using PGMS line with normal Male fertile
line
Photo period more than 14 hours
PGMS line × Normal Male fertile
( Male sterile) ( Male fertile)
Hybrid seed

14. TGMS ( TEMPERATURE SENSITIVE GENETIC
MALE STERILITY
Use in tropical countries in case rice like Crops
Conditions :
Less than 28 * C temperature cause complete Male fertile plant, and more than 30 * C temperature leads to
complete Male sterile plant
Maintenance of TGMS line
Temperature Less than 28 * C
TGMS line
TGMS line ( fertile)
Selfing in isolation

15. Hybrid seed production using TGMS line and Normal Male fertile line
Temperature more than 30 * C
TGMS line × Normal fertile line
( Male sterile) ( Male fertile)
Hybrid seed

16. CIMS ( CHEMICAL INDUCED MALE STERILITY)
1. This non - genetic method including Male sterility involves the use of chemicals called
hybridizing agents or gametocides like GA3 , NAA, MH ,sodium/Zinc methyl arsonate.
2. This method is useful for plants with bisexual flowers in which it is difficult to obtain genetic or
cytoplasmic genetic Male sterility ( GMS or CGMS )
3. The ideal gametocides are
● Selectively induced Male sterility without adversely affecting the female sterility.
● Must not be mutagenic.
● Should consistently produce complete ( more than 95 % ) Male sterility.
● Should not be hazards to the environment.

17. For developing hybrids using gametocides
➢ The female line should have a synchronous flowering habit.
➢ The should response to chemical treatment
➢ The parent should possess good out crossing trait.
Important factors that's decide the efficiency of chemical gametocides
➢ The correct doses of chemicals.
➢ Appropriate stage of treatment.

18. Advantages :
➢ Simplified procedure of hybrid seed production.
➢ Multiple and diverse germplasm available as parent .
➢ Any line could be taken as female .
➢ Increase Chance of developing desirable and heterotic hybrid.
➢ Multiple cytoplasm occurs as female parent .
Disadvantages :
➢ Environmental effect on sterility could cause seed purity problem .
➢ Incomplete Male sterility and not heritable.
➢ Multiple treatment required.

19. 😊Thank You 😊