growth cycle of yam development evaluation protocol for tuber earliness/growth period

1. Yam physiology
Key word: growth cycle, growth period varietal difference, senescence
Increasing the capacity of research
technicians in breeding
28th July 2015
Ryo Matsumoto (visiting scientist from JIRCAS, Japan )

2. 1. Growth cycle of yam
2. Development evaluation protocol for tuber
earliness/growth period
3. Evaluation of tuber earliness characteristic
4. Summary
Today’s topic

3. Growth cycle of Yam
General
During the growth cycle, there are five distinct phases,

4. Changing in dry weight of aerial and tuber part during growth cycle
Growth cycle of Yam
0
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Jun Jul Aug Sep Oct Nov Dec
Dryweight(g)
Tuber weight
Aerial part weight

5. 0
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Jun Jul Aug Sep Oct Nov Dec
Dryweight(g)
Tuber weight
Aerial part weight
Growth cycle of Yam
Phase 1: Tuber germination • The stem is still devoid of expanded leaves,
reducing the transpiring surface as much as
possible to optimize the reserves for root
development.

6. Growth cycle of Yam
Phase 2: Foliage Development • Characterized by a very rapid and massive
increase in leaf area and ends the
dependence of the yam plant on the tuber
sett.
• The plant reaches self-sufficiency
(autotrophy)
0
100
200
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Jun Jul Aug Sep Oct Nov Dec
Dryweight(g)
Tuber weight
Aerial part weight

7. Growth cycle of Yam
Phase 3: Rapid Tuber bulking • Nutrient are translocated from canopy to
tuber
• The more rapid is tuber development and
the greater its final size.
0
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Jun Jul Aug Sep Oct Nov Dec
Dryweight(g)
Tuber weight
Aerial part weight

8. Growth cycle of Yam
Phase 4: Foliage senescence, tuber mature
0
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Jun Jul Aug Sep Oct Nov Dec
Dryweight(g)
Tuber weight
Aerial part weight

9. Development evaluation protocol for tuber earliness
Phase 5: Dormancy • Mature, freshly harvested tubers cannot
sprout and they enter a dormancy phase
which can last for leads than a month to up
to 5 months.
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Jun Jul Aug Sep Oct Nov Dec
Dryweight(g)
Tuber weight
Aerial part weight

10. 0
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Jun Jul Aug Sep Oct Nov Dec
Dryweight(g)
Five growth phase
Growth cycle of Yam
Phase 1 Phase 2 Phase 3 Phase 4 Phase 5

11. Growth cycle of Yam
General
During the growth cycle, there are five distinct phases, which can vary
according to growing condition, spices and genotype.
Phase 1: Tuber germination
Phase 2: Foliage development
Phase 3: Tuber bulking
Phase 4: Foliage senescence, tuber mature
Phase 5: Dormancy

12. Late mature variety
Early mature variety
Varietal deference in tuber growth pattern of yam (White yam: D. rotundata)
Growth cycle of Yam
Days after planting
Tubermaturityrate(%)
 3 plants x 3 rep. x 6 times x 3 year rep.
 Aerial part:
• Dry weight
• Sprouting date
• Senescence date
 Tuber part:
• Dry tuber weight
Early mature variety:
 Tuber growth stop earlier

13. • Dispersion of risk at famer field (dry stress, insect attack at….)
• Extension of period to provide fresh yam tuber at the materket
• Expand yam growing area for food security
Growth cycle of Yam
Why do we need to get different growth period variety for famer and customer ??
What is advantage point that farmer has different maturity variety ??

14. • Rice 20 cm x 20 cm
• Yam 100 cm x 100 cm
If you have to plan 100 seeds / seed tubers for
experiment, how big field do you need ??
Rice: 400 cm2 (4 m2)
Yam: 10000 cm2 (100m2)
New protocol which is
simple and non-distractive
for earliness evaluation
were required
Questions !!!

15. **Senescence index
Senescence index of aerial part is weekly recorded till surveyed plants each
variety had completely been senescence. Senescence level is classified into
the five levels and quantified.
Level 1 No senescence leaf・・・ a
Level 2 25% senescence・・・・・・ b
Level 3 50% senescence・・・・・・ c
Level 4 70% senescence・・・・・・ d
Level 5 100%senescence・・・・・ e
Senescence index=
{(1 ×No. of level 1 plant)+(2×No. of level 2 plant) + (3×No. of level 3 plant) +
(4×No. of level 4 plant) + (5 ×No. of level 5 plant) / 9}
a b c d e
Development evaluation protocol for tuber earliness
Focus point: Senescence index

16. After planting days
Senescenceindex
Late mature variety
Early mature variety
Development evaluation protocol for tuber earliness
Start senescence aerial part,
Early mature variety：160 DAP
Late mature variety：１80 DAP
Changing in senescence index during growth period in early and late mature variety

17. Days after planting
Senescenceindex
Relationship between tuber growth and senescence of aerial
part
Tuber growth
Senescence index
• Tuber growth finish
• Photosynthesis finish
• Start senescence of aerial part
Start senescence starting
time was confirmed to be
index parameter for earliness
of tuber growth by plant
physiologically staudy
Early mature variety:
 Tuber growth stop earlier
 Senescence of aerial part
also earlier
Development evaluation protocol for tuber earliness
Late mature variety
Early mature variety
→ Non-distractive evaluation
Tubermaturityrate(%)

18. Evaluation of tuber earliness characteristic
Genetic resources (D. rotundata)
Genetic resources
(447 lines as core collection) Diversity research set
(DRS-EDITS: 100 lines)
Smaller,
But retain diversity
 Experimental design
• 3 plants
• Randomized block design with 2 rep.
 Characterization
• Morphological traits
• Growth period

19. No.ofaccessions
Days from sprouting day to
foliage senescence start day
Evaluation of tuber earliness characteristic
Days from sprouting day to foliage senescence start day in DRS

20. No.ofaccessions
Days from sprouting day to
foliage senescence start day
Evaluation of tuber earliness characteristic
Days from sprouting day to foliage senescence start day in DRS
New acc. will be selected for
parental material to develop
new variety !!!!!
Early mature variety
Late mature variety

21. Summary
Plant Physiology is very important for understanding the plant growth
Whole genome sequence of D. rotundata had
already done by IBRC under collaboration
research program between JIRCAS, IITA and
IBRC.
High quality phenotyping will be key factor for
further improvement of yam cultivation
To conduct high quality phenotyping,
plant physiology knowledge is very
important

23. FemaleMale Monoecious
Evaluation of sex / Flowering characteristic