Abstract
Harvest index (HI) is the ratio of grain to total shoot dry matter and is as a measure of reproductive efficiency. HI is determined by interactions between genotypes (G), environment (E), and crop management (M). Historic genetic yield gains due to breeding in wheat have largely been achieved by increasing HI. Environmental factors are important for HI and include seasonal pattern of water supply and extreme temperatures during crop reproductive development. Wheat production in Australia has been dominated by fast-developing spring cultivars that when sown in late-autumn will flower at an optimal time in early spring. Water limited potential yield can be increased by sowing slower developing wheats with a vernalization requirement (winter wheat) earlier than currently practiced such that their development is matched to environment and they flower at the optimal time. This means a longer vegetative phase which increases rooting depth, proportion of water-use transpired, and transpiration efficiency by allowing more growth during winter when vapour pressure deficit is low. All these factors can increase biomass accumulation, grain number and thus grain yield potential. However higher yields are not always realized due to a lower HI of early sown slow developing wheats compared to fast developing wheats sown later. Here, we evaluate genotype × management practices to improve HI and yield in early sown slow developing wheat crops using 6 field experiments conducted across south eastern Australia from 2014 to 2018 in yield environments ranging from ~1 to ~4.7 t/ha. Practices included low plant densities (30-50 plants/m²), mechanical defoliation, and deferred application of nitrogen fertilizer. Lower plant densities had similar yield and HI to higher plant densities. Defoliation tended to increase HI but reduce yield except when there was severe stem frost damage. Deferring nitrogen had a variable effect depending on starting soil N and in crop rainfall. All management strategies evaluated gave variable HI and yield responses with small effect sizes, and we conclude that none of them can reliably increase HI in early sown wheat. We propose that genetic improvement is the most promising avenue for increasing HI and yield in early sown wheat, and postulate that this could be achieved more rapidly through early generation screening for HI in slow developing genotypes than by crop management.
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Claims 8
Claim · model-written summary
Lower plant densities gave similar yield and harvest index to higher plant densities in early sown wheat.
- Taxon
- wheat
Triticum aestivume0 - Treatment
- Lower plant densitiese1
- Outcome
- yield and HIe1
- Direction
- similare1
- Comparator
- higher plant densitiese1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Here, we evaluate genotype × management practices to improve HI and yield in early sown slow developing wheat crops using 6 field experiments conducted across south eastern Australia from 2014 to 2018”
e1“Lower plant densities had similar yield and HI to higher plant densities”
Claim · model-written summary
Defoliation tended to increase harvest index in early sown wheat.
- Taxon
- wheatTriticum aestivume0
- Treatment
- Defoliatione2
- Outcome
- HIe2
- Direction
- increasee2
- Qualifier
- tended toe2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Here, we evaluate genotype × management practices to improve HI and yield in early sown slow developing wheat crops using 6 field experiments conducted across south eastern Australia from 2014 to 2018”
e2“Defoliation tended to increase HI but reduce yield except when there was severe stem frost damage”
Claim · model-written summary
Defoliation tended to reduce yield in early sown wheat, except when severe stem frost damage occurred.
- Taxon
- wheatTriticum aestivume0
- Treatment
- Defoliatione2
- Outcome
- yielde2
- Direction
- reducee2
- Qualifier
- except when there was severe stem frost damagee2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Here, we evaluate genotype × management practices to improve HI and yield in early sown slow developing wheat crops using 6 field experiments conducted across south eastern Australia from 2014 to 2018”
e2“Defoliation tended to increase HI but reduce yield except when there was severe stem frost damage”
Claim · model-written summary
Deferring nitrogen had a variable effect on wheat depending on starting soil N and in-crop rainfall.
- Taxon
- wheatTriticum aestivume0
- Treatment
- Deferring nitrogene3
- Outcome
- effecte3
- Direction
- variablee3
- Qualifier
- depending on starting soil N and in crop rainfalle3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Here, we evaluate genotype × management practices to improve HI and yield in early sown slow developing wheat crops using 6 field experiments conducted across south eastern Australia from 2014 to 2018”
e3“Deferring nitrogen had a variable effect depending on starting soil N and in crop rainfall”
Claim · model-written summary
All evaluated management strategies gave variable harvest index and yield responses with small effect sizes in early sown wheat.
- Taxon
- wheatTriticum aestivume0
- Treatment
- management strategiese4
- Outcome
- HI and yield responsese4
- Direction
- variablee4
- Qualifier
- with small effect sizese4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Here, we evaluate genotype × management practices to improve HI and yield in early sown slow developing wheat crops using 6 field experiments conducted across south eastern Australia from 2014 to 2018”
e4“All management strategies evaluated gave variable HI and yield responses with small effect sizes, and we conclude that none of them can reliably increase HI in early sown wheat”
Claim · model-written summary
None of the management practices can reliably increase harvest index in early sown wheat.
- Taxon
- wheatTriticum aestivume0
- Outcome
- increase HI in early sown wheate4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Here, we evaluate genotype × management practices to improve HI and yield in early sown slow developing wheat crops using 6 field experiments conducted across south eastern Australia from 2014 to 2018”
e4“All management strategies evaluated gave variable HI and yield responses with small effect sizes, and we conclude that none of them can reliably increase HI in early sown wheat”
Claim · model-written summary
Genetic improvement is proposed as the most promising avenue for increasing harvest index and yield in early sown wheat.
- Taxon
- wheatTriticum aestivume0
- Outcome
- increasing HI and yield in early sown wheate5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Here, we evaluate genotype × management practices to improve HI and yield in early sown slow developing wheat crops using 6 field experiments conducted across south eastern Australia from 2014 to 2018”
e5“We propose that genetic improvement is the most promising avenue for increasing HI and yield in early sown wheat”
Claim · model-written summary
Early generation screening for HI in slow developing genotypes may achieve faster HI gains than crop management.
- Taxon
- wheatTriticum aestivume0
- Outcome
- early generation screening for HI in slow developing genotypese6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Here, we evaluate genotype × management practices to improve HI and yield in early sown slow developing wheat crops using 6 field experiments conducted across south eastern Australia from 2014 to 2018”
e6“postulate that this could be achieved more rapidly through early generation screening for HI in slow developing genotypes than by crop management”
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