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  • 1
    Electronic Resource
    Electronic Resource
    Genetic improvement of bread wheat (Triticum aestivum L.) in Argentina: relationships between nitrogen and dry matter (1990)
    Springer
    Euphytica 50 (1990), S. 63-71 
    Details
    ISSN: 1573-5060
    Keywords: Triticum aestivum ; wheat breeding ; genetic improvement with time ; grain nitrogen concentration ; nitrogen economy ; nitrogen utilization efficiency ; Argentina
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Changes in nitrogen (N) economy and N to dry matter (DM) relationships were studied for six cultivars of bread wheat (Triticum aestivum L.) released in Argentina at different times between 1912 and 1980. Experiments were performed on two successive years. N partitioning to reproductive organs was changed both at anthesis and at maturity. Grain N yield (GNY) was associated to both total N accumulated and N partitioning. Most of the changes produced by genetic improvement on N economy at maturity could be explained by parallel changes at anthesis. Neither biological N yield (BNY) at anthesis nor BNY at maturity showed any trend with the year of release of the cultivars. Grain N concentration (GNC) showed a negative trend with the year of release, and was inversely correlated to both grain yield (GY) and harvest index (HI). However, GNC was positively and significantly associated with NHI to HI ratio, indicating that the main reason for its behaviour along this century was the dilution of N on non N compounds. The N utilization efficiencies (NUE) for both GY and grain number were positively affected by breeding. Moreover, modern Argentinian cultivars are as efficient as the best cultivars showed by other authors. It is suggested that to increase GNC together with GY, breeders should improve N accumulation at anthesis maintaining high remobilization of vegetative N.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00023162
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  • 2
    Electronic Resource
    Electronic Resource
    Changes in physiological attributes of the dry matter economy of bread wheat (Triticum aestivum) through genetic improvement of grain yield potential at different regions of the world (1991)
    Springer
    Euphytica 58 (1991), S. 37-49 
    Details
    ISSN: 1573-5060
    Keywords: Biomass ; grain yield ; grain yield components ; harvest index ; Triticum aestivum ; wheat breeding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The understanding of the changes produced by plant breeding on wheat grain yield and on its determinants, through the study of the behaviour of cultivars released at different times during the breeding process, could be a useful tool to define future selection criteria. The aim of this paper was to examine the genetic improvement effects on bread wheat grain yield potential and on its major physiological determinants in different countries. Generally, it seems that the genetic improvement produced important increases in harvest index, but it did not produce important changes in total biomass. The genetic gain in grain yield ranged from 0.58 g m-2 year-1 (India) to 5.84 g m-2 year-1 (Mexico); reflecting important differences among genetic improvement programmes. However, when the comparisons were made in relative values, the difference was much lower, ranging from 0.16% year-1 to 0.90% year-1, for the previously mentioned countries, respectively. Most of the regions showed relative genetic gains of around 0.45% year-1. Similar patterns of relative genetic gains in harvest index were found. Half of the total gain in grain yield in the past was due to genetic gain in grain yield potential. However, it is expected for the future, that further increases in grain yield will rely more on genetic gain than on technologic gain. Thus, a discussion about possible strategies in future breeding programmes of bread wheat is attempted throughout the paper. The changes in grain yield were mostly associated with changes in number of grains per m2 rather than with changes in individual grain weight. It appears that the source: sink ratio during the grain-filling period was very high in old cultivars, whereas the source: sink ratio in modern cultivars is more balanced. Further increases in number of grains m-2 could be compensated by a reduction in individual grain weight, if simultaneous improvement in source strength during grain-filling is not achieved. The crop attributes which have been changed together with the mentioned traits are discussed and alternative selection criteria are suggested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00035338
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  • 3
    Electronic Resource
    Electronic Resource
    Radiation interception and radiation use efficiency of near-isogenic wheat lines with different height (1997)
    Springer
    Euphytica 97 (1997), S. 201-208 
    Details
    ISSN: 1573-5060
    Keywords: dwarfing genes ; wheat ; radiation interception ; radiation use efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Three near isogenic lines of spring wheat grown to determine whether Rht dwarfing alleles alter radiation interception. A field study (involving two sowing dates in two growing seasons) with lines containing different allelic dosage of Rht1 and Rht2 (i.e. dwarf, DD; semi-dwarf, SD and tall SH), was conducted without water and nutritional deficiencies. Dwarfing genes did not modify the timing of occurrence of phenological events. Above-ground biomass at anthesis was reduced by 22% in the DD line in relation of the rest of the lines. However, at maturity accumulated biomass of the DD and SH lines were not significant different. Dwarfing genes increased the light attenuation coefficient (k, with values of 0.48, 0.62 and 0.78 for the SH, SD and the DD line respectively). A similar trend was followed to the leaf thickness (estimated by the specific leaf weight, SLW). Despite the differences observed among the lines, both in k and SLW values, they did not differ significantly in the proportion of incoming radiation intercepted by the canopy, nor in the cumulative intercepted radiation during the pre and post-anthesis periods. Radiation use efficiency (RUE) differed significantly among the lines. While RUE during pre-anthesis was the lowest in the DD line, from anthesis to maturity the lines with Rht alleles showed higher RUE values than the SH line. The low pre-anthesis RUE in the DD lines could be associated with (i) poor canopy architecture due to reductions in leaf sheath and internode lengths and/or (ii) reduced canopy CO2 exchange rate. Post-anthesis RUE was lower than that recorded pre-anthesis in all lines. But the magnitude of the reduction was inversely related to the doses of the Rht alleles. Post-anthesis RUE appeared to be closely and positively associated with the number of grains set per unit biomass at anthesis. This relationship suggests a regulatory effect of the sink size on the efficiency of the crop to convert radiation into biomass during this period.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003061706059
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  • 4
    Electronic Resource
    Electronic Resource
    Intrinsic earliness and basic development rate assessed for their response to temperature in wheat (1995)
    Springer
    Euphytica 83 (1995), S. 175-183 
    Details
    ISSN: 1573-5060
    Keywords: basic development rate ; earliness ; intrinsic earliness ; flowering ; phenology ; temperature ; thermal time ; Triticum aestivum ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The related concepts of basic vegetative period, intrinsic earliness and basic development rate in wheat are examined. These concepts have the common assumption that, if plants are vernalised fully and then grown at long daylength in order to remove any responses to vernalisation and photoperiod, the calendar or thermal time then taken to anthesis will be a characteristic of a genotype that will be heritable. Thus, regardless of temperature, early genotypes will always be earlier than late genotypes (providing there are no vernalisation and photoperiod responses). Using four genotypes, exposed to 50 days of vernalisation, and then grown at 18 h photoperiod under six temperature regimes ranging between 10 and 25°C, it is shown that; (1) no genotype had an absolute basic period as, depending on temperature, durations to anthesis for any one genotype varied by more than 50 days; (2) no genotype had an absolute value for intrinsic earliness (to anthesis), ranging for any genotype by more than 300°Cd depending on temperature; (3) basic development rate was not a single value for a genotype but varied with stage of development; (4) some genotypes changed their ranking for earliness depending on the temperature regime; and (5) genotypes were differentially sensitive to temperature for the subphases prior to anthesis. We conclude that the earliness descriptors should not be considered as static genotypic characteristics but as the result of the interaction between the genotype and temperature. Thus, the apparent earliness trait is likely to be related to temperature sensitivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01678127
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of moisture stress on leaf appearance, tillering and other aspects of development in Triticum tauschii (1995)
    Springer
    Euphytica 86 (1995), S. 55-64 
    Details
    ISSN: 1573-5060
    Keywords: Aegilops squarrosa ; leaf number ; phyllochron ; tillering ; Triticum tauschii ; water stress ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A glasshouse study was conducted to describe the dynamics of leaf and tiller appearance of four accessions of T. tauschii (Tt 04, Tt 17, Tt 65 and Tt 74) and to determine the influence of moisture stress (treatments were high and low moisture, imposed seven days after transplanting) on these and other aspects of development in this wild wheat. Under high moisture conditions, accessions differed greatly in flag leaf dimensions, culm length and seed number per spike, the values being lower in Tt 04 than in the other accessions. Low moisture strongly reduced values for these traits, with Tt 04 being least affected, but overall, there was no apparent association between the values obtained for these variables in the high moisture conditions and the effects of moisture stress. For three of the four accessions, final leaf number on the main culm was significantly lower in the low moisture treatment than in the respective control (P〈0.05), but the differences between treatments (ca. 0.5 leaves or less) were very small. Maximum tiller number, on the other hand, was strongly reduced by low moisture, and initiation of tillering was inhibited until water was reapplied. There were no apparent after-effects of the moisture regime on the rate of subsequent tiller appearance. The four accessions differed in their leaf appearance rates, giving phyllochron values (117–142° Cd leaf-1) within the range reported for hexaploid wheat. Low moisture tended to increase phyllochron, but in only one accession was this effect significant. Thus, depending on the accession, low moisture did not affect, or slightly decreased (by ca. 15–20%) the rate of leaf appearance. These effects were similar to those reported for cultivated wheat suggesting that there would be little scope for using these accessions of T. tauschii in breeding for stress tolerance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00035939
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  • 6
    Electronic Resource
    Electronic Resource
    Has yield stability changed with genetic improvement of wheat yield? (1999)
    Springer
    Euphytica 107 (1999), S. 51-59 
    Details
    ISSN: 1573-5060
    Keywords: wheat ; plant breeding ; yield stability ; environmental index
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effect of plant breeding on yield and their physiological determinants has been widely studied in wheat. However, it is poorly understood how, and to what extent, yield stability has been modified. To attempt a direct analysis of changes in absolute and relative yield stability, data of yield of cultivars released in different eras in different environments were obtained from records from our lab and from the literature. Depending on the availability of data, effects of plant breeding on yield stability of cultivars released in Argentina, Australia, Italy and the United Kingdom were evaluated using a quantitative approach. In this paper it was assumed that the slope of yield vs. environmental index estimates the instability of the cultivars. In addition, a more qualitative approach for Mexico, and the former USSR complemented this analysis. There was a clear decrease in yield stability assessed in absolute terms as a consequence of wheat breeding. In Argentina, Australia, Italy and the UK this decrease was related to the magnitude of yield increases. However, the decrease in yield stability in Argentina and Australia was less than for Italy and the UK, particularly so during the last 30 years. Modern cultivars released in Argentina and Australia showed a trend to maintain yield stability as a percentage of their yield similar to that of their predecessors, while the two European countries analysed tended to a slight decrease in yield stability even in relative terms. The complementary, less quantitative evaluation of Mexico and the former USSR appeared to confirm the quantitative trends described for the other countries, i.e. a general decrease in yield stability (assessed in absolute terms) with genetic gains in yield potential.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003579715714
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