Modelling floral induction for different apple tree cultivars: an innovative approach to disentangle the intertwined effects of hormonal signals, carbohydrate status and plant architecture

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Modelling floral induction for different apple tree cultivars: an innovative approach to disentangle the intertwined effects of hormonal signals, carbohydrate

status and plant architecture Benoit Pallas

To cite this version:

Benoit Pallas. Modelling floral induction for different apple tree cultivars: an innovative approach to disentangle the intertwined effects of hormonal signals, carbohydrate status and plant architecture. AgreenSkills Annual Meeting, Oct 2014, Toulouse, France. 2014. �hal-02794925�

Modelling floral induction for different apple tree cultivars: an innovative approach to disentangle

the intertwined effects of hormonal signals, carbohydrate status and plant architecture

Benoît Pallas

(Outgoing Fellow, INRA, UMR AGAP)

Host institution : University of QueensLand

Supervisor : Jim Hanan

Dates of mobility : February 2015 – March 2016

Context and state of art

• Alternate bearing is of key importance for apple tree production and is

characterised by a low production in

OFF years and a high production of too

many fruits of poor quality in ON years.

• The use of chemical products reducing

fruit set during ON years is going to be gradually forbidden.

• Growers are looking for alternative solutions to reduce alternate bearing.

• Preliminary analyses on a bi-parental population showed a large genetic variability in

tree production pattern (irregular, biennial,

regular bearing) (Durand et al., 2012)

• QTLs related to these production and flowering

patterns were indentified (Guitton et al., 2012)

A

B

A

B

Main hypothesis and scientific questions

•

The variability in production patterns is mainly related to the variability in floral

induction occuring one year before flowering in apical and lateral meristems.

• Physiological determinants of floral induction variability are still largely unknown.

• 2 Hypotheses are proposed based on experimental results :

- trophic competition for carbohydrate between growing fruits and meristems

could decrease floral induction during ‘ON’ years (Nielsen and Denis, 2000)

- gibberelins produced by fruit seeds could also lead to a decrease in floral

induction (Bangerth. 2009)

… but production patterns are also strongly correlated with plant architecture (Lauri

and Trottier, 2004) (e.g. genotypes with long shoots display more regular bearing patterns)

• The respective effects of hormones, carbohydrate balance and architecture are difficult to disentagle using experimental approaches.

Using a

modelling approach

to better analyze the

interactions

between these different aspects of plant development and

functionning.

Objectives and description of the project

• The main objective is to include in the Functional Structural Plant Model MAppleT

(Costes et al. 2008) simulating plant architecture over years a sub model to simulate hormonal and carbohydrate fluxes between leaves, fruits and meristems.

•

This sub model will be developped in

University of QueensLand.

• A first model based on models developped at UQ (C-TRAM for carbohydrate fluxes (Cieslak et al., 2011); models for translocation of hormones (Renton et al., 2013)) will be implemented for the sub-unit composed of a

bourse and a bourse shoot in which floral

induction occurs.

•

The model will be built in L-Systems with the plant modelling environment L-Studio

(Karwowski and Prunsinkiewicz, 2004) and will then be integrated in MAppleT to capture the variability in floral induction within plant structure and analyze the impact of plant architecture.

• The model will be calibrated and validated with experiments carried out in Montpellier

First activities and results

• A first experiment was carried out in

summer 2014 in Montpellier on a segregating population (X3263 x Belrène)

• The objectives of the experiment were to :

- define a sub-population displaying large

variability in production patterns. (biennial, irregular, regular) based on floral sequence analysis (Fig. 7).

- quantify hormonal contents in organs

and plant trophic status (photosynthesis

activity (Fig.8), non structural hormonals

contents) for the genotypes with

contrasting production patterns.

• A first dataset useful for modelling

activities is available. This dataset will be complemented in 2015.

References

Bangerth. 2009. Sci. Hort. 122: 153-163; Cieslak et al. 2011. Ann. Bot. 107: 747-764; Costes et al. 2008. Funct. Plant Biol. 35: 936-950; Guitton et al. 2012. J Exp Bot. 63: 131-149; Durand et al. 2013. J Exp Bot 64: 5099-5113. Karwowski and Prusinkiewicz. 2004. FSPM Proceedings. 403-405; Lauri and Trottier. 2004. New Phytol. 163: 533-546; Nielsen and Denis. 2000. Act. Hort. 527: 137-146; Renton et al. 2012. New Phytol. 194: 704-715.

Fig 1. Trees in ON and OFF years (A, B, respectively)

Fig 2. QTLs detected for BBI (index of

alternance) on chromosom 4, for a segregating population (Starkinson x Granny) (Guitton et al., 2012)

Fig 3. Example of two contrasted production

patterns (number of fruits) of two genotypes of a segregating population (Belrène x X3263)

Fig 4. Output of MappleT (Costes et al. ,2008)

Fig 5. The L-Studio modelling environment

(algorithmicbotany.org/lstudio/whatis.html)

Fig 6. A bourse/ shoot

bourse structure.

M: apical meristem (in which floral induction occurs); BS : bourse shoot; LS : bourse shoot leaf; B : bourse; LB: leaf bourse ;F: fruit F B BS LS M LB

Fig 8. Leaf net assimilation for the genotypes with different

production patterns (BvsB & Desynch : regular genotypes, ON & OFF: biennial genotypes in ON or OFF years)

Production type

BvsB Desync V Desyn F ON OFF

Ne t as s imi lation ( molC0 2 m -2 s -1 ) 0 2 4 6 8 10 12 14 b _b b a b Type effect **

Fig 7. PCA analysis on production variables on the

genotypes of the X3263xBelrène population. (bi-prod, biennial genotypes, in ON or OFF years. Reg: regular genotypes. Prod – and Prod + refer to genotypes with low or high production).