Wheat breeding for stress tolerance: use of chlorophyll fluorescence parameters as selection criterion

Plant Science + Breeding

Hello I am working on exploring mechanism of stress tolerance (drought and salt) in different crops such as wheat, canola, maize sunflower etc. Since photosynthesis is central to biomass (growth and yield) production under stress conditions, it is assumed it can be used as selection criteria in breeding and selection. My experience is genetic variability in gas exchange characters of cultivars are more related with degree of their stress tolerance as compared to chlorophyll fluorescence parameters particularly under salt stress (as Chl Fluorescence parameters changed after 18-24 days after stress and differences in cultivars appeared after 32-36 days). However, under flooding stress, N stress, drought stress, crude oil contaminated soil toxicity etc it rapidly appears. I would like to know the experiences of others in this connection to further proceed it

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Itay cohen

Apr 2016

Hi guys, I see salt stress as very “progressive tax” .while plant is exposed to prolong salt conditions, he accumulate salt in various organs (even roots) and the effect of the stress buildups, and indirectly or direct;y affects plant gas exchange (water potential, dysfunction of key photosytntetic enzymes) …

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Jesse Traub

Apr 2016

Hello Habib-ur-Rehman! I agree with what Andrew said above, and I'll add a few thoughts of my own too. I have done some research on drought and its effects on gas exchange and chlorophyll fluorescence. I agree with you that a mild drought stress will impact gas exchange first while leaving chlorophyll fluorescence unchanged. Parameters like phi2 and NPQ won't be affected until the drought stress actually begins to damage the photosynthetic apparatus, as opposed to just triggering a closure of the stomatal aperture. Still, without too much trouble, I have been able to detect drought-related drops in phi2 in greenhouse plants.

But the other stresses you mentioned (salt, N stress, crude oil contamination) might directly damage the photosynthetic apparatus and cause a lowering in phi2 even in the absence of a change in stomatal conductance. Let us know how your experiments turn out, I would be interested in hearing your results.

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Andrew Wiersma

Apr 2016

I'm not completely sure what the question is, so I will give you some of my thoughts/speculations on salt stress as it relates to photosynthetic efficiency. First, salt stress will likely impact plant water potential which will limit photosynthesis (ie. low water availability = reduced stomatal conductance). Second, salt stress will also affect soil cation exchange capacity which will also limit photosynthesis (ie. reduced Calcium, Magnesium, Potassium, Ammonium, ect. = improper plant cell function due to missing components). Third, extreme salt stress can be toxic to plants and can lead to plant death.

Hello Andrew Wiersma, My questions are 1- Whether chlorophyll fluorescence attributes are highly sensitive to abiotic stresses? 2- Can we detect these chlorophyll fluorescence changes in plants after subjecting them to stress? 3- Can we use them as potential physiological indicator for stress tolerance? 4- Can we use these chlorophyll fluorescence attributes in breeding program to develop stress tolerant crop cultivars? 5- Can we develop QTL markers for these chlorophyll fluorescence attributes?

This year I am going to analyze more than 100 F3 lines of wheat for yield without imposing any abiotic stress. I will check whether chlorophyll fluorescence attributes measured using MultispeQ, Fast chlorophyll a (OJIP test) attributes or Measured through PAM fluorometry (DUAL-PAM-100, WALZ) are better indicator.

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Greg Austic

Apr 2016

Great question... hmmm... I think I'm not the expert but let me see if I can wrangle some in here for you :)