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 )
1. Growth cycle of yam2. Development evaluation protocol for tuber
earliness/growth period3. Evaluation of tuber earliness characteristic4. Summary
Today’s topic
Growth cycle of Yam
General
During the growth cycle, there are five distinct phases,
Changing in dry weight of aerial and tuber part during growth cycle
Growth cycle of Yam
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Tuber weightAerial part weight
Dry
wei
ght (
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Tuber weightAerial part weight
Dry
wei
ght (
g)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.
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)
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Tuber weightAerial part weight
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ght (
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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.
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Growth cycle of Yam
Phase 4: Foliage senescence, tuber mature
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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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Tuber weightAerial part weight
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ght (
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Dry
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ght (
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Growth cycle of Yam
Phase 1 Phase 2 Phase 3 Phase 4 Phase 5
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 germinationPhase 2: Foliage developmentPhase 3: Tuber bulkingPhase 4: Foliage senescence, tuber maturePhase 5: Dormancy
Late mature varietyEarly mature variety
Varietal deference in tuber growth pattern of yam (White yam: D. rotundata)
Growth cycle of Yam
Days after planting
Tube
r mat
urity
rate
(%)
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
• 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 ??
• 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 !!!
**Senescence indexSenescence 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 ・・・ aLevel 2 25% senescence ・・・・・・ bLevel 3 50% senescence ・・・・・・ cLevel 4 70% senescence ・・・・・・ dLevel 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
After planting days
Sene
scen
ce in
dex
Late mature varietyEarly mature variety
Development evaluation protocol for tuber earliness
Start senescence aerial part,Early mature variety : 160 DAPLate mature variety :1 80 DAP
Changing in senescence index during growth period in early and late mature variety
Days after planting
Senescence index
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 varietyEarly mature variety
→ Non-distractive evaluation
Tube
r mat
urity
rate
(%)
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
No.
of a
cces
sions
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
No.
of a
cces
sions
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 varietyLate mature variety
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
FemaleMale Monoecious
Evaluation of sex / Flowering characteristic