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  • 1
    ISSN: 1439-0523
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Maize varieties with improved nitrogen(N)-use efficiency under low soil N conditions can contribute to sustainable agriculture. Tests were carried to see whether selection of European elite lines at low and high N supply would result in hybrids with differential adaptation to these contrasting N conditions. The objective was to analyze whether genotypic differences in N uptake and N-utilization efficiency existed in this material and to what extent these factors contributed to adaptation to low N supply. Twenty-four hybrids developed at low N supply (L × L) were compared with 25 hybrids developed at high N supply (H × H). The N uptake was determined as total above-ground N in whole plants, and N-utilization efficiency as the ratio between grain yield and N uptake in yield trials at four locations and at three N levels each. Highly significant variations as a result of hybrids and hybrids × N-level interaction were observed for grain yield as well as for N uptake and N-utilization efficiency in both hybrid types. Average yields of the L × L hybrids were higher than those of the H × H hybrids by 11.5% at low N supply and 5.4% at medium N level. There was no significant yield difference between the two hybrid types at high N supply. The L × L hybrids showed significantly higher N uptake at the low (12%) and medium (6%) N levels than the H × H hybrids. In contrast, no differences in N-utilization efficiency were observed between the hybrid types. These results indicate that adaptation of hybrids from European elite breeding material to conditions with reduced nitrogen input was possible and was mainly the result of an increase in N-uptake efficiency.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant breeding 112 (1994), S. 0 
    ISSN: 1439-0523
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Selection indices were calculated for simultaneous improvement of relevant forage maize traits. Beside indices based on primary traits [metabolizable energy yield (MEY) and content (MEC), crude protein content (CPC)] determined either in vitro or by near-infrared reflectance spectroscopy (NIRS), we calculated indices based on secondary (five agronomic) traits. The required phenotypic and genotypic covanance matrices were estimated from a series with 120 maize hybrids tested at three sites. Base index, heritability index, optimum index, and restricted index showed only minor differences in the expected gain in total economic worth (ΔH) for the present agricultural conditions in Germany. CPC was the least important primary trait; selection for grain yield, the most suitable secondary trait, resulted in greater ΔH values than any other index. Harvesting the whole plant and subsequently determining MEC by NIRS was the most economic selection procedure with increased economic weighting for MEC at high animal performance levels. In the latter situation, we recommend grain yield trials as a pretest in breeding programmes and official performance trials for variety registration.
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant breeding 98 (1987), S. 0 
    ISSN: 1439-0523
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The importance of epistasis for forage performance and quality traits was studied in early maturing European maize (Zea mays L.) breeding materials. Sixty-six three-way crosses (3W), 33 of the flint x (dent · dent) and 33 of the dem × (flint · flint) type, were compared with the mean of their respective non-parental single crosses (〈inlineGraphic alt="inline image" href="urn:x-wiley:01799541:PBR185:PBR_185_mu1" location="equation/PBR_185_mu1.gif" extraInfo="missing"/〉) using data obtained in six environments. For each of the 11 traits examined, at least 6 out of the 66 three-way crosses displayed significant (P 〈 0.05) epistatic deviations, calculated as 〈inlineGraphic alt="inline image" href="urn:x-wiley:01799541:PBR185:PBR_185_mu1" location="equation/PBR_185_mu1.gif" extraInfo="missing"/〉– 3W. Averaged over crosses and environments, epistatic deviations were highly significant (P 〈 0,31] for 8 trails, but of minor importance except for grain yield. In general, the variance of epistatie deviations was appreciably smaller than the variance of genotype × environment interactions. Highly significant correlations occurred among epistatie deviations for silking date, dry matter content of ear, and dry matter yield of grain and stover. The reliability of predicting the performance of three-way crosses from 2W as opposed to assessing them directly was investigated as a function of the number of test environments. Disturbing e fleets of epistasis on prediction only became important under intense testing (〉 3 or 4 environments), With fewer test environments, both procedures were almost equivalent, due to a smaller influence of genotype × environment interaction on the 〈inlineGraphic alt="inline image" href="urn:x-wiley:01799541:PBR185:PBR_185_mu1" location="equation/PBR_185_mu1.gif" extraInfo="missing"/〉 values, Epistasis is concluded to be of minor importance with regard to the optimum type of hybrid for forage use.
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant breeding 114 (1995), S. 0 
    ISSN: 1439-0523
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Eleven flint inbreds of maize were crossed with 11 dent inbreds according to a balanced incomplete factorial mating design to produce 66 single crosses (2W) in both reciprocal forms. Additionally, six three-way crosses (3W) were also produced in both reciprocal forms. These hybrids were evaluated for 11 forage yield and quality traits in 1983 and 1984 at three sites in Germany. Highly significant reciprocal differences were observed for nine traits in the 2W. The respective variance component estimates amounted to 2–33% of the variance component due to crosses. On average, flint × dent 2W had lower dry-matter content (DMC) than dent × flint 2W and a 1 % greater dry-matter yield (DMY) of forage. Three-way crosses produced on singles exhibited greater DMC (3%) and DMY (5%) of the ear, metabolizable energy content (MEC) of stover (1%), and DMC and DMY of forage (2%) than their reciprocal forms produced on lines. Based on this study, because of their minor importance, routine testing for reciprocal differences among 2W hybrids is not recommended.
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