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Submitted on 22 Jul 2019
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Study of tolerance to natural chilling stress in triploid citrus
Radia Lourkisti, Yann Froelicher, Liliane Berti, Jérémie Santini
To cite this version:
Radia Lourkisti, Yann Froelicher, Liliane Berti, Jérémie Santini. Study of tolerance to natural chilling stress in triploid citrus: Monitoring of photosynthetic and antioxidant performances. 2nd Global conference on Plant Science and Molecular Biology, Sep 2018, Rome, Italy. �hal-02190417�
Selection of diploid (2X) and triploid (3X) hybrid citrus varieties
CONTEXT
Thanks to favorable pedoclimatic conditions, citrus production is extensively developed in Mediteranean area and mostly focused on fresh-fruit market. Nevertheless, it is well established that abiotic stresses, like low temperatures, reduce plant growth, disrupt photosynthesis and the fluidity of membrane cell.
Seedlessness is one of the most consumer expectation on the fresh-fruit market. Polyploidy is an alternative developed to improve tolerance to abiotic stresses.
However, little is known about the response of triploid citrus to low temperatures. The creation of triploid hybrid citrus is an alternative to develop innovative seedless commercial varieties, which present a greater abiotic stress tolerance.
MATERIALS AND METHODS
Rootstock: C35 Citrange (Citrus sinensis ‘Ruby Blood’ x Poncirus
trifoliata)
Hybrid citrus: Fortune mandarin
(Citrus reticulata Blanco) x Ellendale
tangor (Citrus reticulata Blanco x Citrus sinensis (L.) Osb)
Determination of physiological and biochemical parameters
Leaf gas exchange: Net photosynthesis (Pnet) and stomatal conductance (Gs)
Chlorophyll fluorescence: Fv/Fm ratio and Electron Transport Rate (ETR)
Oxidative stress marker and antioxidant enzyme: malondialdehyde (MDA) content and catalase (CAT) specific activity.
2
RESULTS AND DISCUSSION
• The significant decrease of Pnet and Gs was observed during the cold period for all the hybrid varieties (2X and 3X) and their parents.
• In the cold period:
Triploid varieties (h13 and h16) exhibited the highest Pnet and Gs with the lowest decrease.
The largest drop of Pnet and Gs was observed in diploid varieties (d18 and f4)
Low Pnet may be attributed to stomatal closure (low Gs) induced by cold temperatures.
Triploid varieties exhibit an enhanced photosynthetic system during cold stress.
Figure 1. Changes in net photosynthetic rate (Pnet) (A), stomatal conductance (Gs) (B)
• The decline of Fv/Fm was observed for all the varieties during the cold period:
Triploid varieties (h13 and h16) showed a slightest decrease and a higher values of Fv/Fm.
• Different behaviour of electron transport rate (ETR) was observed:
Higher values were found in cold period for diploid varieties and the
'Fortune' mandarin parent.
Triploid hybrid citrus show the lowest photoinhibition with a slight decline of ETR
during the cold period which implies an efficient protection or repair of PSII.
The results are consistent with the enhanced Pnet and Gs in triploid varieties. Cold stress can increase ETR in diploid varietiesalternative electron acceptors
(likeO2) might be available (Mehler reaction).
Figure 2. Changes in chlorophyll fluorescence (Fv/Fm) (A) and electron transport rate (ETR) (B)
• Significant increase of MDA content was observed for all the varieties between warm period and cold period:
The lowest MDA content was found in triploid hybrid (h13)
• Contrasting results were observed in CAT specific activity in cold period:
The highest rise of CAT specific activity was found in triploid hybrid
(h16)
Diploid varieties showed the lowest CAT specific activity
The lower MDA accumulation and higher specific activity of CAT in triploid varieties
suggest an efficient scavenging of reactive oxygen species.
The high activity of CAT is not sufficient to limit oxidative damage in diploid varieties. The results in diploid varieties are consistent with their higher sensitivity of
photochemical performances.
Figure3. Changes in MDA content (A) and in CAT specific activity (B)
CONCLUSION
1
A contrasting response to oxidative stress induced by natural cold temperatures was observed between diploid and triploid varieties:
Triploid varieties showed the lowest drop of photosynthesis and the highest performances of PSII, the slight accumulation of oxidative stress indicators and
the highest specific activity. These parameters suggest an effective response of triploid varieties to natural chilling stress.
Radia LOURKISTI
1, Yann FROELICHER
2, Liliane BERTI
1, Jérémie SANTINI
11CNRS UMR 6134 SPE, Laboratoire de Biochimie et Biologie Moléculaire du Végétal, 20250 Corte, France; 2CIRAD, UPR Amélioration des Plantes à Multiplication Végétative, 20230 San Giuliano, FRANCE
Study of tolerance to natural chilling stress in triploid citrus
Temperature minimum: - Warm period: 18.9°C
- Cold period: 0.1°C
Monitoring of photosynthetic and antioxidant performances
Determine whether the triploidy can enhance tolerance to natural chilling temperatures of hybrid citrus
OBJECTIVES:
The evolution of physiological and biochemical parameters between diploid (2X) and triploid (3X) varieties and their parents in the warm period (black bars) and cold period (white bars) are presented in the following figures:
-82% (A) -630% -29% -34% (B) -36% -20% -88% -69% (A) -38% -30% -8% -13% 43% (B) -18% (A) 54% 33% (B) 64% -66%
Parents: ‘Fortune’ mandarin; ‘Ellendale’ tangor
3X: h13; h16 2X: d18; f4
