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  • Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition  (32)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Potato research 21 (1978), S. 241-248 
    ISSN: 1871-4528
    Keywords: breeding ; selection ; growth correlations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Zusammenfassung In 25 Kartoffelklonen, die auf leichten, trockenen Böden vergleichsweise gute Erträge brachten, wurde 1975 und 1976 das frühe Wachstum gemessen. In jedem Jahr wurden bei 4 Pflanzen pro Klon an drei Ernteterminen folgende Messungen durchgeführt: Gewicht der Stengel. Gewicht der Wurzeln und das Verhältnis Wurzel: Stengel. Die selben Klone wurden zwei Jahre in Feldversuchen auf leichten, trokkenen Böden geprüft. In den Kartoffelklonen wurden genetische Unterschiede in Bezug auf das frühe Wachstum der Stengel, der Wurzeln und das Verhältnis Wurzel: Stengel gefunden (Tabelle 1). Das frühe Wachstum der Stengel war mit dem frühen Wachstum der Wurzeln positiv korreliert, sowohl in der Variation zwischen Einzelpflanzen des Klons als auch Zwischen den Klonen (Tabelle 2, Fig. 1). Bei Klonen mit einem stärkeren frühen Wachstum der Stengel setzte die Knollenbildung früher ein und die Wachstumszeit war kürzer. Klone mit einem höheren Verhältnis Wurzeln: Stengel zeigten eine verzögerte Knollenbildung und eine längere Wachstumszeit (Tabelle 3). Burton (1966) und Raeuber & Engel (1963) weisen daraufhin, dass hoch ertragsreiche Kartoffeln eine schnelle Entwicklung verbunden mit einem verlängerten Wachstum besitzten sollten. Die gezeigten Ergebnisse deuten an, dass die erwähnten Kennzeichen auf einfache Weise im frühen Wachstum von Kartoffelklonen bestimmt werden können: grosses G ewicht der Stengel zeigt eine schnelle Entwicklung an und ein grosses Verhältnis Wurzeln: Stengel ein verlängertes Wachstum. In Versuchsmaterial wurden 2 Klone gefunden, in denen ein höheres Gewicht der Stengel mit einem grösseren Verhältnis Wurzeln: Stengel (Fig. 1) kombiniert ist. Die mögliche Bedeutung dieser Ergebnisse für die Züchtung hoch ertragsreicher Kartoffeln wird diskutiert.
    Abstract: Résumé Dans 25 clones produisant bien en sols légers et déficients en eau, la croissance en début de végétation a été mesuré en 1975 et 1976. Chaque année, pour chaque clone, à trois dates de récolte, les mesures suivantes ont été effectuées sur 4 plantes: poids des pousses, poids des racines et rapport racines/pousses. Les mêmes clones ont aussi été testés pendant deux ans au champ, en sols légers et déficients en eau. Des différences génétiques ont été trouvées entre clones au niveau de la croissance des pousses, des racines, du rapport racines/pousses (tableau 1). Des corrélations positives intraclones et interclones entre croissance des pousses et des racines sont notées (tableau 2, fig. 1). Les clones qui produisent plus grandes pousses tubérisent plus tôt et ont une durée de végétation plus courte. Ceux qui ont un ratio racines/pousses plus élevé ont un retard de tubérisation et une durée de végétation prolongée (tableau 3). Burton (1966), Raeuber & Engel (1963) suggèrent qu’un bon rendement correspond à un développement précoce et rapide de la plante et à une végétation prolongée. Les résultats montrent que ces éléments peuvent être déterminés de façon simple en début de végétation des clones: un poids de pousse élevé indique un développement rapide et précoce et un rapport racines/pousses élevé indique une végétation de longue durée. Dans le matériel expérimenté, 2 clones présentaient à la fois le poids de pousses le plus élevé et le ratio racines/pousses le plus élevé (fig. 1). La possibilité d’utiliser les résultats pour la création de variétés productives est discutée.
    Notes: Summary Genetic differences have been found between potatoclones in early growth of shoots, early growth of roots and in the roots/shoots ratio. The early growth of shoots was positively correlated with the early growth of roots both in the variation of individual plants within a clone and in the variation of individual clones. Clones with greater early shoot growth exhibited earlier tuber growth and had a shorter growing period. Clones with a higher roots/shoots ratio exhibited delayed tuber formation and a longer growing period. The possibility of applying these results to the selection of high-yielding clones is discussed.
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  • 2
    ISSN: 1871-4528
    Keywords: seedling generation ; selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Simple phenotypic, genotypic and environmental correlation coefficients were calculated from one year's data for nine characters in F1 seedlings of 72 crosses and 18 parents of potato (Solanum tuberosum L.). Crosses were made in a line x tester model having 12 female lines and six male testers. The experiment was designed as a randomized block replicated three times at Kufri, Simla (India) during the 1979–80 crop season. Positive phenotypic and genotypic correlations of 1000-TPS weight were found with total tuber yield, number of leaves on the main shoot, number of shoots per plant and harvest index. The results suggest that 1000-TPS weight could be used when attempting to select for yield and other characters in F1 seedlings.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Euphytica 26 (1977), S. 841-845 
    ISSN: 1573-5060
    Keywords: Fragaria × ananassa ; strawberry ; processing ; canning ; pigment ; colour ; selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary It is possible to select strawberry cultivars that give a satisfactory, naturally coloured canned product as an alternative to the commercially dyed one. Spectrophotometric measurements of the syrup from cans, the canned fruit and fresh fruit were compared with visual scoring. A preliminary screening for colour based on visual assessment of fresh flesh colour is possible.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Euphytica 33 (1984), S. 455-463 
    ISSN: 1573-5060
    Keywords: Chrysanthemum morifolium ; chrysanthemum ; temperature ; flowering ; selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The number of days to flowering and the number of flowers per plant were studied at 12, 13, 15 and 17 C night temperature in 79 F1 populations from 15 parents. Only a few F1 plants flowered earlier than their parents; the majority flowered at the same time, later or not at all. The number of flowers of the F1 plants was higher than that of the parents. Genetic analyses showed a broad sense heritability of 70% for days to flowering and flower number and a highly significant GCA effect for days to flowering. The progenies and parents that flowered early at one temperature were generally early at all temperatures.
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  • 5
    ISSN: 1573-5060
    Keywords: Lycopersicon esculentum ; tomato ; temperature ; leaf area ; epidermal cells ; selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary An investigation was carried out into the genotypic variation in the response to temperature of leaf area in tomatoes. Differences between genotypes in the response of the area of a leaf to contrasting temperature regimes were found, and this was due to variation in the number of epidermal cells. The epidermal cell size showed little response to temperature. The results are discussed in relation to the potential for selection for improved leaf area and the development of a rapid screening test for cold tolerance.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Euphytica 33 (1984), S. 355-362 
    ISSN: 1573-5060
    Keywords: Lycopersicon esculentum ; tomato ; temperature ; leaf area ; leaf initiation ; selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Genotypic variation in the response to temperature of the rate of leaf production is reported. Leaf production was measured as the rate of successive leaves passing a specific length and by dissecting plants to obtain the rate of leaf initiation. These results together with the results of leaf size from the previous paper. are compared to the effect of temperature on the total leaf area. The use of information from these experiments in selecting for increased leaf area at low temperature is discussed.
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  • 7
    ISSN: 1573-5060
    Keywords: Lolium perenne ; perennial ryegrass ; selection ; yield ; evaluation ; competitive conditions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The performance of six lines of perennial ryegrass (Lolium perenne L.) which had been selected for three generations for production under spaced plant conditions were assessed under increasing levels of competition, namely spaced plants, drills, miniplots and large sown plots. Successful selection for yield under spaced plant conditions was not accompanied by comparable production patterns in the alternative managements. The extreme situation occurred in swards where a significant decline in production was encountered. Negative or no relationships were found in the establishment year between spaced plant production and yield in the alternative conditions whereas in the first harvest year positive correlations occurred between spaced plants, drills and miniplots and only the latter with plots. These varying patterns of performance are considered in relation to the prediction of sward behaviour and the appropriate environment for selection.
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  • 8
    ISSN: 1573-5060
    Keywords: Triticum aestivum L. ; bread wheat ; landraces ; genetic variation ; path-analysis ; yield and yield components ; selection ; Iran
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract There is renewed interest in wheat landraces as important sources of genetic variation for agronomic characters. Fifty-three pure lines of bread wheat (Triticum aestivum L.) derived from seven landraces collected from southeastern Iran were used to estimate genetic variation and heritability for 13 developmental and quantitative characters. Path-analysis was used to partition the genetic correlations between grain yield and six grain yield-related traits. Mean values of landraces were also compared with three improved cultivars from California and Iran. Genotypic differences among the landraces and among the pure lines collected from the landraces were highly significant for all characters considered. Compared with the modern cultivars, the landrace genotypes were, on average, later in days to heading and taller than the cultivars but had lower values for number of grains per spike, 1000-grain weight, grain yield and harvest index. Some landrace genotypes were similar to the modern cultivars for grain yield. Moderate to high genetic variation was displayed by number of grains per spike, number of spikes per plant, 1000-grain weight, and harvest index. The heritability estimates ranged from 59% for grain yield to 99% for days to anthesis. Expected genetic advance (as % of the mean) was ≈34% for number of spikes per plant, number of grains per spike, and 1000-grain weight. Days to heading and to anthesis correlated positively with number of spikes per plant, shoot biomass, and straw biomass but negatively with number of grains per spike and harvest index. The strong direct effect of number of spikes per plant on grain yield was completely counterbalanced by its indirect negative effects via number of grains per spike and 1000-grain weight. Number of grains per spike and 1000-grain weight were positively correlated with grain yield, and they had large direct effects. These two characters, however, were negatively correlated and exhibited a substantial counterbalance effect via one another and via number of spikes per plant. The landraces could be improved by intercrossing the promising genotypes identified in this study, with simultaneous selection for earliness, fewer number of spikes per plant, greater number of grains per spike and heavier grains. For further improvement, crossing programs between the landraces and introduced germplasm may be necessary.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Euphytica 96 (1997), S. 41-48 
    ISSN: 1573-5060
    Keywords: adaptation ; Chenopodium quinoa ; development ; plant density ; quinoa ; selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Developmental patterns were studied in five groups of quinoa lines from different maturity classes in three years, and measured on five occasions between bud formation and seed set. Knowledge of how the developmental stage develops through the growing season is of importance in the breeding and selection of quinoa lines. Ranking of lines for earliness was consistent over growing seasons, and therefore it was concluded that selection for earliness could be performed at an early stage, i.e. the beginning of July. A growing period greater than 150 days would normally be regarded as too long and risky in Northern Europe, but in the three years under investigation it was possible to harvest lines of the green type with a longer growing period. The total growing period for the lines tested ranged from 109 to 182 days. The vegetative phase and the total growth period were significantly longer for green types than seed types in all years. Duration of the seed set period differed between seed and green types, and between years. In the spring and early summer of the drought year, 1992, both vegetative and seed set periods were shorter than for the other years. It must be concluded that seed types originating from Chile were adapted for growth under North European conditions. Although seed harvest of green types can occur in Denmark, they should preferably be grown at a more southerly latitude.
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  • 10
    ISSN: 1573-5060
    Keywords: clusters ; inheritance ; pod weight ; selection ; yield components ; Vigna unguiculata ; vegetable cowpea ; genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The F2 and backcrosses of a cross between two vegetable cowpea (Vigna unguiculata L. Walp) varieties with contrasting characteristics were evaluated for pod yield and its components, with the aim of understanding the genetic basis of these characteristics. A four-parameter model incorporating the additive, dominance and additive × additive genetic components fitted the data for pod yield and clusters per plant. The additive and additive × additive effects were positive and were larger than the dominance component. The relatively large additive and the predominantly positive dominant effects suggest that selection would be effective. Pod weight had high broad (84%) and narrow sense heritability (75%) and can be effectively selected for in the early generations. The study suggested that vegetable cowpea improvement programs should focus on selecting for clusters per plant and average pod weight in the early generations, while selection for dry pod yield could be delayed to later generations. It was concluded that pods per plant may be a useful selection criterion in multi-location trials aimed at selecting for stability of yield.
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  • 11
    ISSN: 1573-5060
    Keywords: epistatis ; genetics ; Lycopersicon pimpinellifolium ; Ralstonia solanacearum ; selection ; bacterial wilt ; tomato ; Lycopersicon esculentum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The genetic nature of bacterial wilt resistance in tomato was studied in two crosses based on the number of days of survival (quantitative) in the field before the appearance of wilt symptoms. Significant differences were observed between generation means in both crosses (LA 1421 × Cascade and LA 1421 × Caraibo). This study indicates that resistance identified in Lycopersicon esculentum var. cerasiforme LA 1421 may be different from that derived from L. pimpinellifolium. However, the genetic mechanism seems to be complex with a duplicate form of epistasis. Results suggest that selection for resistance from crosses between LA 1421 and Cascade should preferably be delayed until a high level of fixation of genes is attained. The variation observed in the F2 and BC2 progeny of the Caraibo cross, suggested that genetic combination between the two resistance sources can lead to higher levels of resistance.
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  • 12
    Electronic Resource
    Electronic Resource
    Springer
    Euphytica 95 (1997), S. 39-44 
    ISSN: 1573-5060
    Keywords: sugarcane ; selection index ; selection ; seedlings ; ratoon ; Saccharum ; Saccharum officinarum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract General (GSI) and specific (SSI) selection indices were constructed for three open-mating populations of sugarcane (Saccharum spp.) seedlings and their ratoon stages. Though specific indices were found to be the most effective in improving mean brix yield in their own source populations, but the GSI was better to SSI in other populations as indicated by higher mean values and more number of superior clones at selection and evaluation stages. This indicated the wider applicability of the GSI over SSI. Inspite of better expected genetic advance through GSI in ratoon crop, the actual gain in brix yield attained, through GSI, was better in seedlings.
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  • 13
    ISSN: 1573-5060
    Keywords: cowpea severe mosaic virus ; genetics ; selection ; screening ; resistance ; tolerance ; Vigna unguiculata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract P1, P2, F1, F2, BC1 and BC2 generations of four resistant × susceptible crosses and three resistant × resistant crosses of cowpea (Vigna unguiculata L. Walp) were screened for resistance to cowpea severe mosaic virus (CPSMV), in an insect protected screen house. The segregation ratio, at maturity, showed a 63 susceptible : 1 resistant ratio in the F2 generation indicating that resistance is governed by three major genes. The backcross tests and the F3 test confirmed this. The intermediate levels of symptoms observed in the F1 generation and the progression of symptom expression in the F2 generation suggested that resistance is gene dosage dependent. The genetic basis of immunity, tolerance, high level of resistance is discussed based on the three gene model. Delayed symptom expression was evident in genotypes with one or two susceptible alleles. The implications of delayed expression of symptoms in selection and breeding for resistance to CPSMV are discussed.
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  • 14
    Electronic Resource
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    Springer
    Euphytica 26 (1977), S. 157-168 
    ISSN: 1573-5060
    Keywords: Phaseolus vulgaris ; common bean ; selection ; bulk breeding ; competition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effect of bulk breeding on yield and its components was studied in two high-yielding and two low-yielding bean crosses until the F6 generation. It was found that bulk breeding on the whole did not alter the mean values in the high-yielding crosses, but that there was a steady increase in the mean values of the low-yielding crosses with generation. As well as mean values the use of variance as a determinant of cross potential was also studied. It was found for characters markedly influenced in their expression by the environment, of which grain yield is the prime example, that progeny variance did not differ significantly from parental variance. It was concluded that interplant competition was the factor of the environment responsible for this effect.
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  • 15
    Electronic Resource
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    Springer
    Euphytica 26 (1977), S. 825-828 
    ISSN: 1573-5060
    Keywords: Tulipa ; tulip ; keeping quality ; ornamental value ; selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Criteria of selection for keeping quality in tulip breeding are reviewed on the basis of a wide range of cultivars and species. The conclusion from an earlier, more limited study that there are large differences in keeping quality between cultivars in several characteristics is confirmed. The choice of the number of days between the onset of flowering and perianth drop as the best criterion is reconsidered because in some cases perianths may remain on the plant long after they have lost their attractiveness. It was found that the sequence in which the various stages (50% discoloration. perianth curving, perianth drop, leaves and stem no longer upright) are reached is not the same for all cultivars and species. None of these phenomena can therefore be used exclusively as criterion of keeping quality. A more comprehensive criterion as the number of days the flower maintains its ornamental value, is useful when commercial cultivars are compared, but for breeding and physiological research attention should be given to all individual aspects of the keeping quality of flower. stem and leaves.
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  • 16
    ISSN: 1573-5060
    Keywords: Phaseolus vulgaris ; common bean ; selection ; bulk breeding ; genetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effects of bulk breeding on yield and its components in two high-yeilding and two low-yielding bean populations when grown at crop densities are interpreted in terms of gene action and selection. There was considerable additive variation in the crosses, dominance effects were variable but tended to be negative. The results were compared with results obtained at low density by another worker with the same populations, and this showed that interpretations of gene action in hybrid vigour depend on the test environment used. The interpretations were also compared with plant breeding interpretations made on the same material (Hamblin, 1977), and it was found that a single pattern of response to natural selection, in plant breeding terms, may be explained by more than one genetic interpretation and, conversely, a single genetic interpretation may result in different patterns of response in plant breeding terms. The value of composite crosses in plant breeding are discussed and it is concluded that there is a greater chance of producing improved lines from a large number of simple crosses than from a smaller number of composite crosses.
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  • 17
    ISSN: 1573-5060
    Keywords: Yield ; selection ; micro-environmental variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Moving average and polynomial response surfaces were used to estimate systematic micro-environmental variation within four different F3 selection environments. At low density the response surfaces were efficient in estimating systematic variation. At high densities random variation due to intergenotypic competition predominates. It is concluded that the two major factors rendering single plant selection for yield inefficient are competition within selection plots and genotype-season interactions between the selection and test generations.
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  • 18
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    Euphytica 28 (1979), S. 37-40 
    ISSN: 1573-5060
    Keywords: Triticum aestivum ; wheat ; selection ; single seed descent ; early generation yield tests
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary If selection based on F3 yield tests is to be effective, the yield tests must be successful in discriminating among yield genotypes. The available literature indicates that simple tests with limited or no replication are not very effective, although more extensive, replicated tests may be. Data from an experiment comparing F3 yield tests with a single seed descent procedure showed that F3 selection based on a two-replicate test with single seed descent procedure did not justify the extra work involved.
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  • 19
    ISSN: 1573-5060
    Keywords: Zea mays L. ; maize ; selection ; morphological traits ; physiological traits ; tropics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Selection criteria to accelerate improvement of tropical maize (Zea mays L.) are needed because resources are limited and foods needs are growing. Yield efficiency (YE) (yield per unit leaf area), the reported grain yield-limiting factor in tropical maize, should be compared with grain yield (GY) (yield per unit land area) as selection criteria for rapid improvement of tropical maize. Selections for GY and for YE were conducted in two open-pollinated tropical maize cultivars that contrasted in morphological and physiological traits. Effectiveness of each selection criterion, changes in morphological and physiological traits, and density responses of synthetics associated with each selection criterion were studied. S1 lines were extracted in each population and evaluated in their area of adaptation at three locations in Southeastern Zaire during the 1976–77 growing season. The ten high yield-efficient and ten high yielding S1 lines in each population were separately combined to produce synthetics for high YE and high GY, respectively. The two synthetics selected in each population were compared with their original population at four densities (40 000, 60 000, 80 000 and 100 000 plants/ha) at Kaniama, Shaba, Zaire during 1977–78. Selecting for GY effectively increased GY, but also tended to maintain or increase excessive vegetative growth. Selecting for YE effectively reduced plant vegetative growth in one population and individual leaf size in the other population. It did not increase GY or YE because environmental and genetic factors that operate on YE were confounded. Neither selection criterion improved density tolerance. Maize breeding should emphasize selecting for combined criteria of GY and YE to achieve high GY, high YE, and density tolerance.
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  • 20
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    Euphytica 33 (1984), S. 227-232 
    ISSN: 1573-5060
    Keywords: Triticum aestivum ; wheat ; selection ; inbreeding ; maternal inheritance ; kernel color
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Data are presented which support early generation selection for white kernel color in the progeny of red/white kernel wheat crosses which are segregating at 12 or more loci for yield (or any other trait of interest). The optimum generation for selecting white kernels is determined by the frequency of seeds produced with the potential to produce plants having desired quantitative alleles from both parents, and by the frequency of white kernels produced. The F2-produced seed (F3 embryo) is shown to be the optimum generation for selecting white kernels, given that 12 or more loci are segregating for a quantitative character such as yield. When the red parent is a 2 or 3 loci red genotype, selection among F4-produced seed for white kernel color may be desirable when 5 or fewer genes are segregating for the second trait. The results have direct application for all highly heritable, recessive, sporophytic traits.
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  • 21
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    Euphytica 33 (1984), S. 313-319 
    ISSN: 1573-5060
    Keywords: Phalaris aquatica ; phalaris ; pasture grass ; over-summering buds ; dormancy ; half-sib analysis ; heritability ; selection ; drought survival
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The relative ability of the underground buds of a Mediterranean perennial grass species to break dormancy in response to summer rain was compared between individual plants and between half-sib families in two experiments with broadly-based breeding populations under different environmental conditions. Significant genetic variation was found in summer regrowth activity in both experiments. The narrow-sense heritability of the ratio of new to old, dead tillers after summer rain under spaced plant conditions at a relatively cool site was 0.40±0.16. Under sward conditions at a warm site, the narrow-sense heritability of an index of summer regrowth potential on a half-sib family mean basis was 0.36±0.08. Summer regrowth activity was negatively but weakly correlated with flowering time (rg=−0.22), and strongly positively correlated with early autumn herbage yield (rg=0.79). Summer regrowth activity was not genetically correlated with seedling size or herbage yield in the second or third growing seasons. These correlations are different in sign or magnitude from those observed in collections of Mediterranean ecotypes from which the breeding populations were derived by crossing to Australian cultivars and recurrent selection for vigour and persistence. The correlations in Mediterranean populations therefore are not due to pleiotropic effects; they can be altered by recombination. Phenotypic variance relative to the population mean was considerable in both experiments, and hence the level of the responsiveness of dormant buds to summer rainfall should be manipulable readily by selection. The possible effects of altered responsiveness on long term survival and productivity in several different environments are discussed.
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  • 22
    ISSN: 1573-5060
    Keywords: Oryza sativa ; rice ; aluminium-resistance ; selection ; stress ; in vitro ; hydroponic cultures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A selection procedure is described that isolated Al-resistant individuals from a sensitive rice (Oryza sativa L.) genotype. Somaclonal variation was used as the only source of variability and selection pressures were applied at both callus and regenerated plant levels. When 10 week-old, embryo-derived calli were submitted to different Al stresses for a period of 20 weeks. After this in vitro stress period, selected calli were grown during 18 weeks, without selection pressure, on regeneration media. Selection pressures were applied on regenerated plants (R0), and 9 R0 plants which produced seeds were selected. The transmission of the Al-resistant character to the R1, R2, R3 and R4 generations was then investigated, and three plant lines which had an increased percentage of Al-resistant plants till the fourth generation of self-pollination, were identified. One was from a callus maintained on an Al-free medium. The efficiency of in vitro selection pressures was therefore debated.
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  • 23
    ISSN: 1573-5060
    Keywords: aster ; Aster novi-belgii ; breeding ; correlation coefficients ; flower induction ; selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Bolting and flowering of Aster novi-belgii seedlings as well as correlations between characteristics within seedling populations and between seedlings and their vegetatively propagated offspring were investigated in order to improve breeding efficiency. In seedlings of A. novi-belgii, flower induction was observed without vernalization. Seedlings initially formed a rosette, but bolting was a prerequisite for development of a normal flowering shoot. Bolting was promoted by long photoperiods as compared to short days. The shortest time from sowing to anthesis was recorded when plants were grown under long photoperiods until the main stem was at least 5 cm long, and then moved to short photoperiods. A large variation in time to anthesis, plant height, branching ability, and flower size and color was found among the seedlings within all crosses. Magnitude and significance of correlations between some characteristics varied among crosses. The more consistent correlations seem mainly to be due to natural courses of plant growth and development. High correlations between seedling characteristics and their vegetatively propagated offspring were only found for flower hue. Lower, but significant correlations were found for flower color intensity, plant height and branching ability. There were no significant correlations for the time-to-anthesis between the two groups of plants.
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  • 24
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    Euphytica 28 (1979), S. 161-167 
    ISSN: 1573-5060
    Keywords: Triticum aestivum ; grain yield ; selection ; progeny bulks
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Three methods were evaluated as potential aids in identifying superior crosses early in the breeding program: (1) F1 yield, (2) F2 yield, and (3) midparental yield. Two sets of spring wheat (Triticum aestivum L. em. Thell.) crosses and parents were evaluated in replicated single row plots in F1 and in replicated multi-row plots in F2 over a period of five years. On the basis of F1 yields, two of the highest yielding and two of the lowest yielding crosses in each set were chosen for a more detailed selection study in subsequent generations. In Set 1, random F2 head selections for each of the selected four crosses were evaluated in 3-row yield plots in F4. In Set 2, F2 plant selections were made on the basis of head weight and the highest yielding 10% evaluated for yield in F4. Lines of crosses identified as high yielding in F1 had significantly greater mean yields in F4 than those of crosses that were low yielding in F1. The high yielding crosses had three to four times as many lines yielding in the top 10% in F4 than did the low yielding crosses. Correlations for yield were obtained between F1 and F2 in different years, F2 and midparents in the same year, lower or no correlations between F1 and midparents in the same year, and no correlations between F1 and midparent and F2 and midparent in different years. It is suggested that larger plot sizes rather than single rows be used to evaluate parents. Midparental yield, F1 yield and F2 yield tests are recommended as a progressive set of screening tests for a given set of crosses to effectively maintain the superior crosses in the breeding program.
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  • 25
    ISSN: 1573-5060
    Keywords: selection ; genetic variance ; heritability ; fruit breeding ; Diospyros kaki ; Japanese persimmon ; soluble solids ; kaki
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In fruit breeding, the selection is often based on individual plant performance, therefore, the expected proportion of offspring having genotypic values exceeding a given critical value (EP) was estimated for soluble solids content (SSC) in Japanese persimmon (Diospyros kaki Thunb.). A simple model was used in the study: the mean value of offspring in a full-sib family is solely determined by the regression of that on midparental value (MP) and all families have an equal within-family variance due to segregation. The population consisted of 39 full-sib families with three offspring each. Between-family variance was much smaller than within-family variance. Genetic variance for MP was much smaller than that for offspring. The EP therefore was not highly affected by the regression. Based on the parental mean performance of 35 fruits on a single tree for three years, the proportion of offspring having SSC higher than 18% was estimated as 32%, 50% and 69% for three groups of MP differing in SSC, i.e. 16.5%, 17.5%, and 18.5%, respectively. The distributions which were predicted using those results for 246 offspring from 46 families, and 86, 44, 43 and 31 offspring from four selected families, respectively, were largely consistent with those observed.
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  • 26
    ISSN: 1573-5060
    Keywords: red clover ; resistance tests ; Sclerotinia trifoliorum ; selection ; Trifolium pratense
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Sclerotinia crown and stem rot is the most destructive disease on red clover in areas with cool seasons including North America and Europe. An artificial inoculation test in controlled conditions has been developed in order to evaluate resistance to this fungus in individual plants. Measured drops of ascospore suspension were applied to detached clover leaflets and disease severity scored on a visual scale. Clovers from 16 cultivars and 12 ecotypes were tested for resistance to Sclerotinia trifoliorum. The results obtained for cultivar resistance are in agreement with those of other tests described in the literature. Moreover, repeated individual evaluations on detached leaflets from the same plant was successful in detecting genotypic variation within clover populations.
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  • 27
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    Plant and soil 188 (1997), S. 101-106 
    ISSN: 1573-5036
    Keywords: acid soil tolerance ; Al tolerance ; selection ; Triticum aestivum L. ; wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Soil acidity in the Great Plains of the USA can reduce forage and grain yields of winter wheat, primarily by Al toxicity. Indigenous cultivars may vary in seedling tolerance to Al toxicity, but the benefit that Al tolerance provides to forage and grain production is not well documented in this region. Backcrossed-derived lines of ‘Chisholm’ and ‘Century’ were selected with an additional gene from ‘Atlas 66’ conferring Al tolerance in solution culture. Our objective was to determine the impact of this source of Al tolerance on forage production prior to the jointing stage and subsequent grain yield. Experiments were conducted at several locations on non-limed (pH=4.5–4.7) and limed soils (pH=5.2-6.1) in Oklahoma. Two cultivars (‘TAM 105’, susceptible; ‘2180’, tolerant) with extreme differences in Al tolerance were used as controls . In limed conditions, forage and grain production did not differ between Al-tolerant and -susceptible genotypes, indicating a neutral effect of the Atlas 66 gene in the absence of Al toxicity. Despite visual differences in early-season plant vigor in non-limed acid soil, the Al-tolerant selections did not yield greater season-long forage than their susceptible parents. At sites where Al saturation in the non-limed soil exceeded 30%, spike production at maturity was nearly doubled in the Century background by the addition of Al tolerance, but final grain yield was not significantly improved. In the Chisholm background, grain yield was improved 50 to 74% by Al tolerance. The magnitude of the agronomic benefit of Al tolerance was highly influenced by the edaphic environment and genetic background. Acid soils of the Great Plains appear highly variable in Al toxicity; hence, consideration of the target environment is essential to predict the potential impact of Al tolerance selected in solution culture.
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  • 28
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    Euphytica 28 (1979), S. 473-480 
    ISSN: 1573-5060
    Keywords: Hordeum vulgare ; barley ; breeding systems ; recurrent selection ; selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A critical examination of three representative barley development programs from three barley producing areas of the world reveals that the evolution of each can be explained by the concepts of simple or phenotypic recurrent selection. Typically, each has utilized only 13 to 16 separate genetic sources in their program. Most of the sources were introduced over 50 years ago and have been progressively recombined through a simple recurrent selection process. The time period required for selection, testing, and reincorporation of improved genetic recombinants into the breeding program, or the completion of a cycle of recurrent selection, ranged from 6.5 to 10.5 years. If the major operative force in barley breeding is recurrent selection, then additional attention should be given to increasing the genetic base and reducing the time required to complete cycles of selection.
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  • 29
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    Euphytica 32 (1983), S. 85-95 
    ISSN: 1573-5060
    Keywords: Lolium perenne ; perennial ryegrass ; selection ; yield
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Selection for yield under spaced plant conditions was carried out for three generations in five lines of Lolium perenne derived from natural populations and of known genetic organisation, and for two generations from within the bred variety S.23. Evaluation of all selected generations under comparable spacing conditions revealed that overall a slow positive response to selection had been achieved. The magnitude and direction differed for the several lines and was inconsistent. The variable response was accounted for by low heritability, genotype x year interaction and the small population size with high intensity of selection imposed.
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  • 30
    ISSN: 1573-5060
    Keywords: banana ; Musa spp. ; Mycosphaerella fijiensis ; black leaf streak ; resistance ; selection ; toxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The results of our experiments suggest that toxin(s) of Mycosphaerella fijiensis would be involved neither in infection initiation, nor in the hypersensitive reaction in highly resistant cultivars but could serve at most as secondary determinant of the pathogenicity, contributing to the lesion expansion in cultivars exhibiting partial resistance to Black Leaf Streak disease. Moreover, the effects of toxin(s) on chlorophyll fluorescence, as well as preliminary electron microscopy observation, suggest that chloroplasts could be a precocious site of action of the toxin(s). Therefore, in vitro heterotrophic tissues would not be a suitable target to perform the screening with such toxin(s). The prospects and limitations of M. fijiensis toxin(s) for screening banana for resistance to Black Sigatoka are highlighted.
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  • 31
    ISSN: 1573-5060
    Keywords: breeding ; in vitro ; mutagenesis ; pear ; selection ; Pyrus communis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In vitro shoots of four pear (Pyrus communis L.) cultivars, 'Conference', 'Doyenné d'Hiver', 'Passe Crassane' and 'Bartlett', were irradiated with gamma rays (3.5 Gy). Around 1000 microcuttings of each cultivar were treated. After three subcultures, microcuttings from both the irradiated shoots and additional non-irradiated shoots were rooted; plants obtained were used to establish a survey orchard in Ostellato (Ferrara), Italy. For the first 2 years in the field, growth and survival were observed, but no data were collected. Subsequently, field surveys were conducted to characterize the population and identify mutants for vegetative traits. Trees that showed phenotypic evidence of vegetative growth characteristics more desirable than those shown by the overall population and by control plants were selected and measured for three years. Traits used for selection were small tree size, wide branch angle and short internodes. Frequencies of variants with compact habit varied with cultivars from 0.5% to 2.7% of irradiated trees. Effect of mutagenic treatment and efficacy of the selection methods are discussed.
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  • 32
    ISSN: 1572-9788
    Keywords: barley ; intron ; NPT II ; reporter genes ; selection ; tobacco
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Intron sequences from monocotyledonous and dicotyledonous origin were used to abolish marker gene expression in prokaryotes (Escherichia coli and Agrobacterium tumefaciens) but permit expression in selected eukaryotic systems using the eukaryotic specific splicing mechanism. A 1014 bp maize Shrunken-1 (Sh 1) intron 1 flanked by exon1 and exon2 sequences was cloned into the N-terminal of the NPT II-coding region. Transient gene expression analysis revealed that the modified neomycin phosphotransferase II (NPT II) gene, driven by the cauliflower mosaic virus (CaMV) 35S promoter, is expressed in barley protoplasts, but poorly expressed in tobacco protoplasts. In dicotyledonous cells AU-rich sequences are known to be important for efficient splicing and therefore an attempt was made to improve expression of the NPT II gene, containing the Sh 1 intron 1, in tobacco by increasing the AU content from 57% to 69%. Reverse transcriptase PCR analysis of RNA from transiently expressed NPT II transcripts from tobacco protoplasts revealed that despite the increase in AU-content, NPT II was still poorly expressed. Cryptic splice sites were identified as one possible cause for missplicing of the Sh1 intron 1 in dicots and poor levels of expression. Alternatively, cloning of the 198 bp intron 2 of the potato STLS 1 gene (81% AU) into the N-terminal part of the NPT II-coding region resulted in proper expression of NPT II in tobacco as well as in barley protoplasts and abolished marker gene expression in prokaryotes. The successful insertion of an intron into a selectable marker gene which completely abolishes gene expression in prokaryotes, without affecting expression of chimeric genes in monocotyledonous and dicotyledonous plant cells provides a suitable system to reduce the number of false-positives in transgenic plant production.
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