Abstract
Hybrids of wheat, barley, and triticale are expected to possess higher yield performance and yield stability compared to inbred lines. Assessment of yield performance as well as yield stability requires the evaluation of genotypes in plot-based yield trials across multiple environments. Evaluation of genotypes under stress conditions can be associated with increased field heterogeneity, which may result in imprecise estimates of genotypic values. The assessment of yield stability requires intensive testing in many environments, and it would be interesting to know how many test environments are required to reliably estimate yield stability. The key objectives of the present thesis were to (1) investigate optimal strategies to analyze field trials with high error variance due to spatially varying drought stress, (2) identify the required number of test environments to precisely estimate yield stability of individual barley genotypes, and (3) examine yield performance and yield stability of wheat, barley, and triticale hybrids and lines. Drought stress at two locations of a winter triticale trial caused increased field heterogeneity, resulting in lower heritabilities compared to the four non-stress locations. It was found that heritability could be increased by modeling incomplete block and row effects, by using visual scorings of drought stress intensity as covariates in an analysis of covariance, and by modeling a spatial covariance between adjacent plots. The most suitable model can be identified using the Akaike Information Criterion. In addition, it has to be ensured that the covariate is independent from genotypic effects and that it is linearly related with the response variable. Dynamic yield stability of genotypes was frequently found to depend strongly on the specific set of test environments. When the genotypes were evaluated in different environments, e.g. in the following year, the ranking in yield stability could be different. This would result in a low heritability. Theoretical assumptions and empirical studies showed that heritability can be increased when the number of test environments is increased. Five series of barley registration trials with a reduced number of 16 to 27 genotypes evaluated in 39 to 45 environments were used to investigate the relationship between magnitude of heritability of yield stability and number of test environments. Based on a cross-validation approach, it was found, that at least 40 test environments should be used to obtain a heritability of 0.5. Magnitude of heritability, however, varied strongly within and between series. Therefore, depending on the respective set of environments and genotypes, more or less test environments can be needed. Yield performance of wheat hybrids produced using chemical hybridizing agents (CHA) or cytoplasmic male sterility (CMS) was well investigated in other studies reporting around 10% midparent heterosis for grain yield. In the present thesis, CMS-based barley hybrids were compared with parental inbred lines and unrelated commercial inbred lines in breeding and registration trials. Midparent heterosis was around 10%. The comparison with commercial inbred lines in the registration trials revealed that hybrids could compete with and partially surpass outstanding inbred lines. Triticale hybrids, produced using CMS, were evaluated for grain yield at up to 20 environments with their parents and commercial inbred lines. Midparent heterosis amounted to 3% and no hybrid outyielded the best inbred line. The low yield performance of triticale hybrids is probably associated with CMS-system, since CHA-based triticale hybrids showed a midparent heterosis around 10% in early studies, which is comparable to the midparent heterosis found in wheat and barley. Yield stability of CHA-based wheat as well as CMS-based hybrids of barley and triticale was compared with yield stability of parental and commercial inbred lines on group level. The wheat and barley hybrids showed on average significantly higher dynamic yield stability compared to inbred lines, but the triticale hybrids did not. In the barley registration trials, hybrids had the highest dynamic yield stability on average. The CMS-based triticale hybrids, however, showed on average significantly lower dynamic yield stability as their female parents and the commercial inbred lines across 20 environments. In conclusion, hybrids of wheat and barley possessed an increased yield potential as well as an enhanced dynamic yield stability. In contrast, the CMS-based triticale hybrids showed only marginal yield advantages coupled with low dynamic yield stability. Further research is required to increase economical competitiveness of hybrids in all three crops, to identify and eliminate the reasons for poor performance of CMS-based triticale hybrids and to investigate the suitability of dynamic yield stability measures to identify vigorous and stress tolerant genotypes.
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Claims 20
Claim · model-written summary
Drought stress at two locations of a winter triticale trial increased field heterogeneity.
- Taxon
- winter triticale
×Triticosecalee1 - Treatment
- Drought stress at two locationse1
- Outcome
- field heterogeneitye1
- Direction
- increasede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat, barley, and triticale”
e1“Drought stress at two locations of a winter triticale trial caused increased field heterogeneity”
Claim · model-written summary
Drought stress at two locations of a winter triticale trial lowered heritabilities compared with the four non-stress locations.
- Taxon
- winter triticale×Triticosecalee1
- Treatment
- Drought stress at two locationse1
- Outcome
- heritabilitiese1
- Direction
- lowere1
- Comparator
- the four non-stress locationse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat, barley, and triticale”
e1“Drought stress at two locations of a winter triticale trial caused increased field heterogeneity, resulting in lower heritabilities compared to the four non-stress locations”
Claim · model-written summary
Heritability could be increased by modeling incomplete block and row effects, by using visual drought scorings as covariates, and by modeling spatial covariance between adjacent plots.
- Taxon
- wheat, barley, and triticale
.jpg?width=60)
Hordeum vulgare
Triticum aestivum×Triticosecalet0 - Treatment
- modeling incomplete block and row effectse1
- Outcome
- heritabilitye1
- Direction
- increasede1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
t0“wheat, barley, and triticale”
e1“It was found that heritability could be increased by modeling incomplete block and row effects, by using visual scorings of drought stress intensity as covariates in an analysis of covariance, and by modeling a spatial covariance between adjacent plots”
Claim · model-written summary
The most suitable model for analysing these field trials can be identified using the Akaike Information Criterion.
- Taxon
- wheat, barley, and triticaleHordeum vulgareTriticum aestivum×Triticosecalet0
- Outcome
- most suitable modele1
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat, barley, and triticale”
e1“The most suitable model can be identified using the Akaike Information Criterion”
Claim · model-written summary
Dynamic yield stability of genotypes depended strongly on the specific set of test environments.
- Taxon
- wheat, barley, and triticaleHordeum vulgareTriticum aestivum×Triticosecalet0
- Treatment
- specific set of test environmentse1
- Outcome
- dynamic yield stabilitye1
- Direction
- depend stronglye1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat, barley, and triticale”
e1“Dynamic yield stability of genotypes was frequently found to depend strongly on the specific set of test environments”
Claim · model-written summary
Heritability can be increased when the number of test environments is increased.
- Taxon
- wheat, barley, and triticaleHordeum vulgareTriticum aestivum×Triticosecalet0
- Treatment
- number of test environmentse1
- Outcome
- heritabilitye1
- Direction
- increasede1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat, barley, and triticale”
e1“Theoretical assumptions and empirical studies showed that heritability can be increased when the number of test environments is increased”
Claim · model-written summary
At least 40 barley test environments should be used to obtain a heritability of 0.5 for yield stability.
- Taxon
- barleyHordeum vulgaree2
- Treatment
- test environmentse1
- Outcome
- heritabilitye1
- Value
- at least 40 test environmentse1
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat, barley, and triticale”
e1“Based on a cross-validation approach, it was found, that at least 40 test environments should be used to obtain a heritability of 0.5”
e2“Five series of barley registration trials with a reduced number of 16 to 27 genotypes evaluated in 39 to 45 environments were used”
Claim · model-written summary
The magnitude of heritability of yield stability varied strongly within and between barley series.
- Taxon
- barleyHordeum vulgaree2
- Outcome
- magnitude of heritabilitye1
- Direction
- varied stronglye1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat, barley, and triticale”
e1“Magnitude of heritability, however, varied strongly within and between series”
e2“Five series of barley registration trials with a reduced number of 16 to 27 genotypes evaluated in 39 to 45 environments were used”
Claim · model-written summary
CMS-based barley hybrids had a midparent heterosis of around 10%.
- Taxon
- barleyHordeum vulgaree3
- Material
- CMS-based barley hybridse3
- Outcome
- Midparent heterosise3
- Value
- around 10%e3
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat, barley, and triticale”
e3“In the present thesis, CMS-based barley hybrids were compared with parental inbred lines and unrelated commercial inbred lines in breeding and registration trials. Midparent heterosis was around 10%”
Claim · model-written summary
CMS-based barley hybrids could compete with and partially surpass outstanding commercial inbred lines in registration trials.
- Taxon
- barleyHordeum vulgaree3
- Material
- CMS-based barley hybridse3
- Outcome
- hybrids could compete with and partially surpass outstanding inbred linese4
- Direction
- partially surpasse4
- Comparator
- commercial inbred linese4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat, barley, and triticale”
e3“In the present thesis, CMS-based barley hybrids were compared with parental inbred lines and unrelated commercial inbred lines in breeding and registration trials”
e4“The comparison with commercial inbred lines in the registration trials revealed that hybrids could compete with and partially surpass outstanding inbred lines”
Claim · model-written summary
CMS-based triticale hybrids had a midparent heterosis of 3% for grain yield.
- Taxon
- Triticale×Triticosecalee1
- Material
- Triticale hybridse1
- Outcome
- Midparent heterosise2
- Value
- 3%e2
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat, barley, and triticale”
e1“Triticale hybrids, produced using CMS, were evaluated for grain yield at up to 20 environments with their parents and commercial inbred lines”
e2“Midparent heterosis amounted to 3%”
Claim · model-written summary
No CMS-based triticale hybrid outyielded the best inbred line for grain yield.
- Taxon
- Triticale×Triticosecalee1
- Material
- Triticale hybridse1
- Outcome
- grain yielde1
- Direction
- outyieldede2
- Comparator
- best inbred linee2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat, barley, and triticale”
e1“Triticale hybrids, produced using CMS, were evaluated for grain yield at up to 20 environments with their parents and commercial inbred lines”
e2“Midparent heterosis amounted to 3% and no hybrid outyielded the best inbred line”
Claim · model-written summary
The low yield performance of triticale hybrids is probably associated with the CMS system.
- Taxon
- triticale×Triticosecalee1
- Outcome
- low yield performance of triticale hybridse1
- Qualifier
- probably associated with CMS-systeme1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat, barley, and triticale”
e1“The low yield performance of triticale hybrids is probably associated with CMS-system”
Claim · model-written summary
Wheat and barley hybrids had on average significantly higher dynamic yield stability than inbred lines.
- Taxon
- wheat and barleyHordeum vulgareTriticum aestivume1
- Material
- hybridse1
- Outcome
- dynamic yield stabilitye1
- Direction
- highere1
- Comparator
- inbred linese1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat, barley, and triticale”
e1“The wheat and barley hybrids showed on average significantly higher dynamic yield stability compared to inbred lines, but the triticale hybrids did not”
Claim · model-written summary
Triticale hybrids did not show higher dynamic yield stability than inbred lines.
- Taxon
- triticale×Triticosecalee1
- Material
- triticale hybridse1
- Outcome
- dynamic yield stabilitye1
- Direction
- did note1
- Comparator
- inbred linese1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat, barley, and triticale”
e1“The wheat and barley hybrids showed on average significantly higher dynamic yield stability compared to inbred lines, but the triticale hybrids did not”
Claim · model-written summary
In the barley registration trials, hybrids had the highest dynamic yield stability on average.
- Taxon
- barleyHordeum vulgaree1
- Material
- hybridse1
- Outcome
- dynamic yield stabilitye1
- Direction
- higheste1
- Setting
- barley registration trialse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat, barley, and triticale”
e1“In the barley registration trials, hybrids had the highest dynamic yield stability on average”
Claim · model-written summary
CMS-based triticale hybrids had on average significantly lower dynamic yield stability than their female parents and commercial inbred lines across 20 environments.
- Taxon
- triticale×Triticosecalee1
- Material
- CMS-based triticale hybridse1
- Outcome
- dynamic yield stabilitye1
- Direction
- lowere1
- Comparator
- their female parents and the commercial inbred linese1
- Setting
- 20 environmentse1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat, barley, and triticale”
e1“The CMS-based triticale hybrids, however, showed on average significantly lower dynamic yield stability as their female parents and the commercial inbred lines across 20 environments”
Claim · model-written summary
Hybrids of wheat and barley possessed an increased yield potential.
- Taxon
- wheat and barleyHordeum vulgareTriticum aestivume1
- Material
- hybridse1
- Outcome
- yield potentiale1
- Direction
- increasede1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat, barley, and triticale”
e1“In conclusion, hybrids of wheat and barley possessed an increased yield potential as well as an enhanced dynamic yield stability”
Claim · model-written summary
CMS-based triticale hybrids showed only marginal yield advantages.
- Taxon
- triticale×Triticosecalee1
- Material
- CMS-based triticale hybridse1
- Outcome
- yield advantagese1
- Direction
- marginale1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat, barley, and triticale”
e1“In contrast, the CMS-based triticale hybrids showed only marginal yield advantages coupled with low dynamic yield stability”
Claim · model-written summary
CMS-based triticale hybrids had low dynamic yield stability.
- Taxon
- triticale×Triticosecalee1
- Material
- CMS-based triticale hybridse1
- Outcome
- dynamic yield stabilitye1
- Direction
- lowe1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“wheat, barley, and triticale”
e1“In contrast, the CMS-based triticale hybrids showed only marginal yield advantages coupled with low dynamic yield stability”