Transcript PPT - GCP21

Swedish University of Agricultural Sciences
www.slu.se
Nutrients regulate formation of
tuberous storage roots in cassava
Per-Olof Lundquist1, Monika Kähr1, Elizabeth Balyejusa Kizito1,2 and
Anna Westerbergh1
1Dept
of Plant Biology and Forest Genetics, Swedish University of Agricultural
Sciences, Uppsala, Sweden
2Med Biotech Laboratories, Kampala, Uganda
Swedish University of Agricultural Sciences
www.slu.se
Dept of Plant Biology and Forest Genetics
Swedish University of Agricultural Sciences
Uppsala, Sweden
Funding from The Swedish Agency for
International Development Cooperation (Sida).
Collaborations with CIAT, Colombia, and
researchers in Uganda.
Cassava research groups:
Anna Westerbergh
- genetic diversity, quantitative genetics, QTL mapping
Christer Jansson, Chuanxin Sun - starch metabolism and gene regulation
Linley Karltun
- food security
earlier Urban Gullberg
- genetic diversity, quantitative genetics
4 PhDs, students from Uganda and Malawi, BIO/EARN project
Swedish University of Agricultural Sciences
www.slu.se
Nutrients regulate formation of
tuberous storage roots in cassava
The experiments were done for two reasons:
• Evaluate how plant cultivation techniques affect
plant growth and storage root formation in
greenhouse conditions.
• Learn about how storage root formation is regulated
in relation to availability of mineral nutrients.
.
Hypothesis excess mineral nutrients (e.g. NPK)
prevents formation of storage roots.
Swedish University of Agricultural Sciences
www.slu.se
Our growth conditions and treatments in short
Computer-controlled growth unit
Rooted cuttings
of cassava
(one clone of offspring of the
selfed accession MTAI 8)
Small pot (0.25 l) Big pot (9.5 l)
Nutrient solution highly diluted and
continuously sprayed to create a mist.
Substrate: mineral wool
Nutrient solution added at
regular intervals.
Nutrients available for the plant
determined by the water-holding
capacity of the substrate.
Nutrient content in the solution
determined as conductivity and pH every
10 min and adjusted immediately to give
essentially free access to nutrients.
Nutrient added at a programmed rate.
Swedish University of Agricultural Sciences
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Theory about plant growth
Plants will grow exponentially if
they have free access to nutrients.
Growth rate limited by genetic
capacity in the given environment.
Relative growth rate (RGR) =
increase in biomass per unit biomass per unit of time
Expressed as “mg g-1 d-1“ or as “% per day”.
Swedish University of Agricultural Sciences
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Nutrient addition and plant growth
Relative addition rate (RAR)
Control plant growth at a specified rate, by adding
nutrients frequently and at a defined rate.
For example, if nutrients are added at a relative
addition rate of 10 % increase per day, the plants can
be controlled to grow at the same relative growth
rate (RGR).
Swedish University of Agricultural Sciences
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Nutrient additions in our experiments
400
Relative addition of nutrient
350
Nutrient addition
400
Big pots
350
Relative addition of nutrient
Pots:
Every 3rd day, constant
amount every
Addition of nutrients
time (100 ppm N, 20 P, 86 K).
Difference in added amounts of
nutrients between big and small pots is
due to different water-holding capacity.
Small pots
300
Becomes nutrient-limited
Free access
at some point in time.
250
200
150
100
50
Growth units:
Programmed to be:
• Free access (FA) to nutrients
• FA - 10 % exponential increase
• FA - 10 – 5 % exponential increase
300
250
200
0
1
8
15
22
29
36
43
50
Time (days)
Nutrient limitation, RAR 10%
150
100
Nutrient limitation, RAR 10%- 5%
50
0
1
8
15
22
29
Time (days)
36
43
50
Swedish University of Agricultural Sciences
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Results: Nutrient availability
Growth rate
The response of the
plants in the growth
units was as expected
for nutrient-limited
plants.
Allocation to
total root
biomass
Swedish University of Agricultural Sciences
www.slu.se
Results: Shoot growth
200
Shoot
weight
(g(g
FW)
Shoot
weight
FW)
Shoot weight at harvest
150
150
100
100
50
50
0
0
Big pots
Small
Free
Big pots
pots
Small
access
0.10-
pots
(FA)
0.05
Time: 49 days
FA-0.10
FA-
34 d 19+34 d 19+12+22 d
= 52 d
= 52 d
Swedish University of Agricultural Sciences
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Storage roots
FA
expressed per shoot weight
FA-10-5
Decreasing nutrient
availability
Storage roots
Swedish University of Agricultural Sciences
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Conclusions
• Production of storage roots is variable depending on nutrient
availability. Storage roots are formed when mineral nutrients become
limiting for overall plant growth.
Hypothesis that there could be an optimum fertilizer level and/or pot
size that would allow good shoot growth with high photosynthetic
capacity that when the fertilizer is used up would allow a high
production of storage roots and starch loading of storage roots.
• Vegetative shoot and root growth has higher sink-strength for the
carbon produced through photosynthesis compared to storage roots
when mineral nutrients are freely available.
• Overall, the findings are consistent with cassava being cultivated in
the field in soils with low nutrient contents.
Swedish University of Agricultural Sciences
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Conclusions, continued
• For controlled studies of storage root traits and other cassava traits,
defined model cultivation systems are useful.
- Relevant for any kind of phenotype characterization (biochemical
analyses, gene expression, development, morphology etc).
Swedish University of Agricultural Sciences
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Acknowledgements
Technical help from Mr Jan Parsby, SLU.
Funding from The Swedish Agency for International
Development Cooperation (Sida).
Swedish University of Agricultural Sciences
www.slu.se
Thank You!
Swedish University of Agricultural Sciences
www.slu.se