Rapid Generation Advance (RGA) is a breeding technique used by IRRI to speed up the rice breeding cycle. It involves growing segregating populations in close spacing under conditions of high temperature and short days to minimize growth duration and produce several generations per year. This allows advancing crosses from F2 to F5 or F6 in one year. RGA faces challenges from insects and heat stress but IRRI has implemented solutions like pest monitoring, sanitation practices, and adjusting fertilizer. Currently IRRI uses RGA to advance around 30,000 breeding lines annually in a high-throughput manner. Future activities include implementing molecular marker-assisted selection in RGA and conducting experiments to further optimize the system.

1. Rapid Generation AdvanceRapid Generation Advance
(RGA)(RGA)
Joseph C. Beredo, R.N.
Assistant Scientist
Irrigated Breeding Team for South East Asia
Plant Breeding Division

2. What is RGA?What is RGA?
• Breeding approach/aspect/technique
• Used in conjunction with SSD
• Production tool for breeding
• Faster production of fixed lines
• Breeding procedure where segregating
populations are raised in an environment
using close spacing, high temperature,
and short days to minimize growth
duration and make several generations
per year. (Vergara et al., 1982)
Low N input
( )
Stress factors
that hasten FLW
and set seed
earlier than field

3. What is Single Seed DescentWhat is Single Seed Descent
• The classic procedure of having a single
seed from each plant, bulking the
individual seeds, and planting out the next
generation
• Seeks to advance crosses to
homozygosity as rapidly as possible while
maintaining maximum genetic diversity for
future selection (Brim, 1966)

4. Why RGA?Why RGA?
• It speeds up the breeding cycle (F2 - F5
or F6 in one year)
• High throughput (40,000+ lines in an
area of 400 m2
)
• It can increase plant protection effects
• Labor distribution can be controlled
• Reduces breeding costs
• Faster variety release

5. DisadvantagesDisadvantages
• Lack of information on potential of
individual or population during RGA
processing
• Possible genetic drifts
• Decreased population size per
generation – needs seed
multiplication at end of target gen!

6. Some highlights (past & present)Some highlights (past & present)
• RGA was first used at IRRI in 1977 by Dr.
Ikehashi (Heu et al., 1982)
• Nippon-bare (released in 1963) was the first
variety bred by RGA with SSD (Maruyama,
1987)
• Since late 2012, IRRI’s irrigated breeding
pipeline was redesigned by using RGA as
the main driver for line development.
• From 2013 to end of 2015, around 50,000+
lines comprising of 100+ crosses were
advanced by the current system
- Collard (2014)
1. Budget constraints (FCR)
2. Changes in PBGB
3. Change of philosophy
4. High demands on IRRI breeders
5. Rate of genetic gain <1%/year

7. F2
F3
F4
F5
F6
F7
FIELD TRIALS
Visual selection
BB, blast, BPH, GLH, quality
>20,000 lines per season
Quality
BB, blast, BPH, GLH, quality
BB, blast, BPH, GLH, quality
Pedigree methodPedigree method
Blast nursery
F8
YEAR1YEAR2YEAR3YEAR4 (Collard, 2014)

8. Rapid generation advanceRapid generation advance
F2
F3
F4
F5
F6
FIELD TRIALS
YEAR1
YEAR2YEAR1
• Plants grown at high
density
• Low fertilizer
YEAR2
NO TRAIT
SELECTION
(Collard, 2014)
Selection is
delayed until F6!

9. The RGA cycleThe RGA cycle
- average 90-105 days (or 3-3.5 months)- average 90-105 days (or 3-3.5 months)

10. PreparationPreparation
• Soil sterilization
• Minuro tray preparation
• Mixing of basal fertilizer to soil
• Soil to minuro trays

12. SeedingSeeding
• One seed is placed on each cell in
principle following SSD, but in
practice 2-3 seeds are seeded to
ensure 95-100% germination and line
survival
• Thinning to 1 plant is done 10 DAS
• Seeding is currently done in
staggered manner (in smaller
batches) to reduce bottlenecks

14. MaintenanceMaintenance
• Topdressing application (21 & 42 DAS)
• Water level monitoring
• Integrated pest management
• Recording of days to flowering (FLW)
and days to maturity (MAT)
• Tiller pruning (main tiller is retained)

16. HarvestHarvest
• 2 types of RGA harvest:
– bulk (standard breeding) and
– plant specific (for genotyping: RILs dev’t)
• Panicles are taken from each plant
• Panicles are carefully stored in a
plastic box or paper bag
• In case of plant specific harvest,
each panicle is stored in a separate
container

18. Seed ProcessingSeed Processing
• Sorting of panicles/seeds per population
• Breaking of dormancy
• Preparation of seeds for next RGA cycle
• If target generation is reached: the
panicles are either stored in the cold room
or threshed to be returned to the customer
for seed multiplication
• For Irrigated-SEA, populations from RGA
are planted in the field for LST, OYT, PYT,
AYT and MET trials.

20. What about the remnant seeds?What about the remnant seeds?
• F3, F4, F5 seeds
• Temporarily stored in cold room
• Storage depends on customers
requests
• Backups seeds in cases of severe pest
pressure
• Usually disposed when the F6
population goes out of RGA  Line
Stage Testing

21. Customers
Preparation phase
Seeding phase
Maintenance
phase
Harvest phase
Seed processing
phase RGA
cycle
(90-105
days)
Breeding4Rice
Advanced materials
CCRD/FCR
Cross prediction/HB
IRSEA Core Breeding
RGA data
1. LST 2. OYT 3. PYT 4. AYT 5. MET
Targetgenerationreached
Seed increase step
(panicle rows)
End generation?
YES
End generation?
NO
Materials and data
flow in RGA

22. Short Day treatmentsShort Day treatments
• Not yet done for current RGA system
• Almost all of the current materials are
photo-period INsensitive
• There are plans for photo-period sensitive
materials in the future
• Prototype for temporary darkroom (use of
black cloth)
• Impractical to do for a large number of
breeding lines – logistics!

23. Molecular-assisted selection (MAS)Molecular-assisted selection (MAS)
in RGAin RGA
• Starting to being implemented to
reduce populations sizes before
going to the field
• Would serve as the main selection
• Plant specific harvest

25. Problems encountered andProblems encountered and
solutions madesolutions made
Sensitive to
biotic and
abiotic stress
RGA  SGA

26. InsectsInsects
• Common greenhouse insects: Ricebugs,
whiteflies, thrips, cutworms, GLH & BPH (nasty!).
• Weekly to monthly pest monitoring
• Basic sanitation (low humidity)
• Sticky traps (yellow sticky cards and tapes)
• Tiller pruning and removal of dry leaves
(eliminates microenvironment)
• UV light traps (use with caution!)
• Spot spraying (non-pyrethroid sprays)
• Use of organic pesticides
• Blanket spraying (if population is high)
• Shutdown period of at least once a year
• Greenhouse should be RGA exclusive! (no field
materials)

27. Hopperburn
in RGA
Cutworm damage

28. Currently in use!
Pending
evaluation and
upcoming
experiment by the
Entom group (Dr.
Buyung Hadi)

29. Panicle sterilityPanicle sterility
• Caused by heat stress at 35˚C and beyond
during reproductive stage
• Heat induces early flowering (good) but too
much of the heat – no harvest
• Use of shading curtains (not enough)
• Use of ventilator turbines so hot air could
escape
• Use of blower fans to circulate the air and
reduce hot spots in the greenhouse
• Fertilizer is also adjusted to compensate
during hot days

31. Vertebrates:Vertebrates:
Birds and RodentsBirds and Rodents
• Immediate action on the earliest sign of
damage
• Completely sealed greenhouse /
screenhouse – any possible entry points
should be covered ASAP!
• Use cover nets on matured populations
• Use of rodent baits and snap traps
• Ask assistance from the rodent experts

33. Developed operation protocolsDeveloped operation protocols
Still optimizing for
Still optimizing for
future publications!
future publications!
NO privateNO private
companies please!companies please!
Not yet final!Not yet final!

34. Demo posterDemo poster

35. IRRI officials, NARS partners, and visitorsIRRI officials, NARS partners, and visitors

36. Current status and future activitiesCurrent status and future activities
• Currently around approximately 30,000 lines for irrigated
materials + some customers (seeded at BG-09 Annex)
• On-going: 4-generation experiment with different
treatments (RCBD, 2 reps)
• Will be implementing 1 week+ shutdown period (CS-08B)
to break pest cycle (late July to early August 2016)
• Will soon be announcing RGA as FCR service (internal
clients only!) after the shutdown
• Currently seeding new batch of irrigated materials (from
LxT) for 2017WS LST
• More experiments to further improve the system (for
discussion)
• Fully implement MAS and GS in RGA (in coordination
with GSL)
• THINK FACTORY! – Continuous improvement

37. THANK YOU FORTHANK YOU FOR
LISTENING!LISTENING!
Rapid Generation Advance

38. Dr. Bert
Dr. Rafiq
Rhulyx
Herman
Edwin
Mark
Joseph