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  • 1
    ISSN: 1573-5060
    Keywords: Brassica campestris ; B. napus ; rapeseed ; drought stress ; selection response ; genetic analysis ; grain yield
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Expectations of yield improvement in environments where drought was the major environmental factor limiting yields were studied in two species of rapeseed. Selection for yield in a drought stressed environment was predicted to be a more efficient selection stategy for yield improvement in dryland situations than selection in a more optimal environment, or selection based on a drought response index. The results indicate that selection for yield in a stressed environment are expected to lead to genetic advances in yield under optimal conditions as well as in a drought index. Selection under well watered conditions, on the other hand, was also expected to lead to correlated increases in yield in droughted environments but to decreases in the drought index. These results were found in both species of rapeseed grown in different water stress situations. The genetic advance in a drought response index was predicted to be greater in B. napus and marginally less in B. campestris if selection was practised for yield in a stressed environment rather than direct selection for the drought index. This was due to the higher heritability estimates in the stressed environments and the positive genetic correlations with yield.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5060
    Keywords: Brassica campestris ; B. napus ; rapeseed ; drought stress ; genetic analysis ; selection index ; grain yield
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The expected improvement in grain yield if selection was made for plant characters measured between flowering and maturity was evaluated in populations of rapeseed (Brassica campestris and B. napus) grown in a droughted environment. Drought was commenced at flowering in each species and measurements were made on plants at the commencement of the drought stress, during the stress treatment and at crop maturity. Substantial genetic and phenotypic variation was observed in yield as well as the different morphophysiological determinants of yield. In B. campestris no single parameter was found to be a suitable alternative selection criterion to yield since the correlated responses in yield if selection was for another character was lower than if selection was for yield alone. By the use of a selection index however, joint selection for yield, as well as harvest index, 1000 seed weight and seeds per pod, was expected to be 20% more effective than direct selection for yield under drought. In the B. napus population direct selection for flowering time or for harvest index was predicted to result in a genetic advance in yield equal to or greater than that obtained by direct selection for yield, whereas joint selection for flowering time and yield should result in a 16% greater yield increase. Selection for increased yield in these populations grown in droughted conditions is discussed.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-5060
    Keywords: Brassica campestris ; turnip rape ; B. napus ; rapeseed ; drought stress ; genetic analysis ; proline accumulation ; chlorophyll stability ; germination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Leaf proline accumulation, leaf chlorophyll stability, and germination at low osmotic potentials have previously been suggested as possible selection criteria for drought resistance in turnip rape (Brassica campestris) and rapeseed (B. napus) (Richards, 1978a). The feasibility of using these characters in a breeding program is reported. These characters were under significant genetic control and were responsive to selection. Broad sense heritabilities ranged from 40% for proline accumulation in both species to 55% for germination rate in B. campestris and 64% for chlorophyll stability in B. napus, however, narrow sense heritabilities for proline and germination were substantially lower. Their use as selection criteria for yield in a Mediteranean drought would be restricted since in B. campestris these characters were not related to yield while in B. napus only a weak association was observed between yield under drought and proline accumulation.
    Type of Medium: Electronic Resource
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