Abstract
Context The companion paper reported that two contemporary cultivars differed constitutively in their average grain weight (AGW) and in their sensitivity to heat waves (HW). It is relevant to elucidate whether the effects of HW are direct on the capacity of the grains to grow or indirect through penalizing post-anthesis (AN) growth and consequently restricting the availability of assimilates for the growing grains. Testing HW with changes in source-strength could help further understanding the causes of the sensitivity of AGW to a HW. This may help to identify strategies in crop management and traits to target in breeding. Objectives To quantify the effects and analyse the causes of post-AN HW on AGW on two contrasting cultivars, considering a double treatment at both stages (pre- + post-AN HW) and whether an increase in source strength through removing alternate rows in the plots by thinning modify the yield penalties. Also, source strength per grain during the effective period of grain filling was either decreased (through a defoliation) or increased (through de-graining) in combination with each of the other treatments. Methods Experiments were carried out in two locations, Lleida and Bell-lloc (NE, Spain). Main treatments consisted in the factorial combination of two contrasting genotypes (Pistolo of high AGW and Sublim of high GN), and three HW that were imposed in the field using installing tents with transparent polyethylene films either at booting (pre-AN HW) or 15 days after anthesis (post-AN HW). An additional HW (combination of pre- and post-AN HW) was imposed in one location while thinning treatment at the onset of stem elongation in the other. Results Across both locations, AGW was consistently higher in Pistolo compared to Sublim. Moreover, the entire distribution of individual grain sizes was higher in Pistolo, with both the lightest (bottom decile) and heaviest (top decile) grains significantly heavier in Pistolo. The main reason for the higher AGW of Pistolo was its higher rate of grain growth, as the duration was similar between both genotypes and also higher potential weight. Post-AN HW, reduced AGW, being Pistolo more sensitive than Sublim. The double HW treatment revealed that exposure to a post-AN HW was markedly less detrimental when preceded by a pre-AN HW. This suggests a non-additive effect on AGW, with prior HW exposure inducing a priming response that mitigated the impact of subsequent stress through antagonistic interactions between the two events. Varying source-sink ratios under heated conditions did not change the weight of the grains noticeably suggesting that direct effects of post-AN HW on the capacity of the grains to grow dominated those mediated by assimilate availability during grain filling. Conclusions The GN–AGW trade-off was not due to limited resources or more small grains. Post-AN HW reduced AGW, but this was lessened in thinned plots, suggesting reduced source strength. HW likely affected AGW via direct (growth capacity) and indirect (assimilate supply) mechanisms. De-graining partially reversed HW effects. Interestingly, combined pre- and post-AN HWs reduced AGW less than post-AN HW alone, suggesting a possible priming effect. Further field studies are needed as multiple heat events may become more common with climate change. Implication As the HW effects include a direct effect component, breeding programs needs to target traits related to grain growth resilience through profiting on genotypic variation in sensitivity of the capacity of the grains to grow; and agronomic practices should consider strategies relate to escaping HWs.
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Claims 15
Claim · model-written summary
Average grain weight was consistently higher in Pistolo than in Sublim.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e1“Across both locations, AGW was consistently higher in Pistolo compared to Sublim”
Claim · model-written summary
The distribution of individual grain sizes was higher in Pistolo.
- Taxon
- wheat
Triticum aestivumt0 - Material
- Pistoloe2
- Outcome
- distribution of individual grain sizese2
- Direction
- highere2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e2“the entire distribution of individual grain sizes was higher in Pistolo”
Claim · model-written summary
The lightest and heaviest decile grains were significantly heavier in Pistolo.
- Taxon
- wheatTriticum aestivumt0
- Material
- Pistoloe3
- Outcome
- lightest (bottom decile) and heaviest (top decile) grainse3
- Direction
- heaviere3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e3“both the lightest (bottom decile) and heaviest (top decile) grains significantly heavier in Pistolo”
Claim · model-written summary
The higher AGW of Pistolo is attributed mainly to its higher rate of grain growth.
- Taxon
- wheatTriticum aestivumt0
- Material
- Pistoloe4
- Outcome
- AGWe4
- Qualifier
- higher rate of grain growthe4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e4“The main reason for the higher AGW of Pistolo was its higher rate of grain growth”
Claim · model-written summary
Grain growth duration was similar between Pistolo and Sublim.
- Taxon
- wheatTriticum aestivumt0
- Outcome
- duratione5
- Direction
- similare5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e5“as the duration was similar between both genotypes and also higher potential weight”
Claim · model-written summary
Pistolo had a higher potential grain weight than Sublim.
- Taxon
- wheatTriticum aestivumt0
- Material
- Pistoloe1
- Outcome
- potential weighte5
- Direction
- highere5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e1“Across both locations, AGW was consistently higher in Pistolo compared to Sublim”
e5“as the duration was similar between both genotypes and also higher potential weight”
Claim · model-written summary
Post-anthesis heat wave reduced AGW, and Pistolo was more sensitive than Sublim.
- Taxon
- wheatTriticum aestivumt0
- Material
- Pistoloe6
- Treatment
- Post-AN HWe6
- Outcome
- AGWe6
- Direction
- reducede6
- Qualifier
- more sensitive than Sublime6
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e6“Post-AN HW, reduced AGW, being Pistolo more sensitive than Sublim”
Claim · model-written summary
Combined pre- and post-anthesis heat waves reduced AGW less than post-anthesis heat wave alone.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- combined pre- and post-AN HWse1
- Outcome
- AGWe1
- Direction
- reducede1
- Qualifier
- lesse1
- Comparator
- post-AN HW alonee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e1“combined pre- and post-AN HWs reduced AGW less than post-AN HW alone”
Claim · model-written summary
A priming response from the pre-anthesis heat wave is suggested to mitigate the impact of the post-anthesis heat wave.
- Taxon
- wheatTriticum aestivumt0
- Outcome
- impact of subsequent stresse2
- Qualifier
- priming responsee2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e2“prior HW exposure inducing a priming response that mitigated the impact of subsequent stress through antagonistic interactions between the two events”
Claim · model-written summary
Varying source-sink ratios under heated conditions did not noticeably change grain weight.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- Varying source-sink ratios under heated conditionse1
- Outcome
- weight of the grainse1
- Direction
- did not changee1
- Qualifier
- noticeablye1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e1“Varying source-sink ratios under heated conditions did not change the weight of the grains noticeably”
Claim · model-written summary
The GN–AGW trade-off was not due to limited resources or more small grains.
- Taxon
- wheatTriticum aestivumt0
- Outcome
- GN–AGW trade-offe1
- Qualifier
- not due to limited resources or more small grainse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e1“The GN–AGW trade-off was not due to limited resources or more small grains”
Claim · model-written summary
Thinning reduced the post-anthesis heat wave penalty on AGW.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- thinned plotse1
- Outcome
- AGWe1
- Direction
- lessenede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e1“Post-AN HW reduced AGW, but this was lessened in thinned plots”
Claim · model-written summary
De-graining partially reversed the heat wave effects on grain weight.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- De-graininge1
- Outcome
- HW effectse1
- Direction
- reversede1
- Qualifier
- partiallye1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e1“De-graining partially reversed HW effects”
Claim · model-written summary
Heat waves likely affected AGW through direct growth-capacity and indirect assimilate-supply mechanisms.
- Taxon
- wheatTriticum aestivumt0
- Outcome
- AGWe1
- Qualifier
- direct (growth capacity) and indirect (assimilate supply) mechanismse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e1“HW likely affected AGW via direct (growth capacity) and indirect (assimilate supply) mechanisms”
Claim · model-written summary
The authors recommend breeding for traits related to grain growth resilience.
- Taxon
- wheatTriticum aestivumt0
- Outcome
- traits related to grain growth resiliencee1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat”
e1“breeding programs needs to target traits related to grain growth resilience”
The same questions in other papers
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