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1.
Summary The efficiency of the honeycomb selection procedure in selecting outstanding genotypes was observed at two interplant distances (d), i.e. d=100 cm, low density, representing noncompetitive conditions and d=15 cm, high density, representing presence of interplant competition. Progress due to selection among the plants grown with and without competition was established by comparison of the plot performance of offspring from selected plants with that of offspring from plants taken at random. The relation between selection intensity and response to selection was observed to detect a possible negative correlation between competing and yielding ability.So far, the results obtained do not yet allow to make a choice between selection of individual plants in presence or in absence of interplant competition. No significant correlation between single plant yield and plot yield was found at any of the two densities. However, response to selection for yield was higher when selecting at low density supporting Fasoulas' preference for selecting single plants in absence of competition. These results must be taken with caution since seed quality and a biassed sample of random plants exerted an important effect on the obtained response to selection.  相似文献   

2.
Summary Three intensities of mass honeycomb selection (14.3,5.3 and 1.6%) applied to an unselected rye population gave respectively an annual yield response of 0.28, -3.69 and -5.20% at 15 cm spacing, and of 4.07, 5.39 and 8.99% at 90 cm spacing. The negative response with competition was explained by strong negative correlation between competing and yielding ability which causes positive skewness because of transposition of low yielders and strong competitors from the left to the right tail of the distribution. The positive response in the absence of competition was mainly due to the increased genotypic differentiation which allowed effective discrimination between high and low yielding genotypes. The efficiency of the selection in the absence of competition was further improved by using the honeycomb designs which adjust soil heterogeneity and application of very high family and individual selection pressures.Two cycles of mass honeycomb selection increased the population yield by 29.4%, one cycle of mass plus one cycle of pedigree honeycomb selection did so by 34.5%. The results are discussed in relation to the selection response and to the efficiency of various breeding schemes.Part of senior author's doctoral thesis  相似文献   

3.
High temperatures, whether of shoot or root, are reported to affect shoot and root growth of various plant species. The scanty information available on the differential response of wheat genotypes to high shoot and root‐zone temperatures triggered this investigation to study the response and adaptation of shoot and root growth of three wheat genotypes to high shoot and root‐zone temperatures during early growth stages. Three wheat genotypes; Fang (heat tolerant), Siete Cerros (heat sensitive) and Imam (recent cultivar adapted to a hot irrigated environment) were grown in soil and hydroponically. Three shoot/root‐zone temperatures (23/23, 23/35 and 35/35 °C for the soil experiment and 22/22, 22/38 and 38/38 °C for the hydroponic experiment) were applied at three‐leaf growth stage. High root‐zone temperature alone or combined with high shoot temperature reduced xylem sap flow rate, root dry weight, root length and root/shoot ratio. Unexpectedly, shoot fresh and dry weights and relative growth rate (RGR) were not significantly affected by the high root‐zone temperature except for the susceptible genotype, Siete Cerros, after prolonged exposure in the hydroponic experiment. In contrast, high shoot/root‐zone temperature significantly reduced shoot fresh and dry weights from as early as the first week of the hydroponic experiment. The 38/38 °C treatment also caused significant reduction in RGR and net assimilation rate during the first 2 weeks, but no significant differences were found during the last 2 weeks compared with 22/22 °C. Interesting responses were observed among genotypes in terms of shoot and root dry weights and root/shoot ratio at 38/38 °C treatment. The heat‐sensitive Siete Cerros showed the least reduction in these traits during the first 2 weeks while the heat‐tolerant Fang and Imam responded by greatly reducing their shoot and root weights. The situation was almost reversed with the duration of treatments such that Siete Cerros became the most affected genotype while Fang and Imam were better adapted to high shoot/root‐zone temperature. Specific root weight was the exceptional trait that increased under high temperature treatments. Results indicate that despite the reduction in root length and weight observed under high root‐zone temperature, shoot growth was not much affected suggesting that the use of suitable cultivar coupled with proper management could alleviate most of high root‐zone temperature effects during early growth stages.  相似文献   

4.
R. J. Pasini  I. Bos 《Euphytica》1990,50(2):147-153
Summary For a second consecutive generation, the efficiency of the honeycomb selection procedure was observed at low and at high density, i.e. interplant distance being 100 cm and 15 cm respectively. Progress due to selection was determined for each of the two plant densities applied by comparing the performance of offspring from selected plants with that of offspring from plants taken at random. The relation between selection intensity and selection response was observed to study the relation between competing and yielding ability in presence and in absence of interplant competition.Compared to results obtained in a previous generation, it is now dared to be more positive about the perspectives of selection in absence of interplant competition. It is tentatively concluded that single plant selection for yield at wide spacing gives a higher progress and allows a better identification of outstanding genotypes. However, the superiority of selection at low density is not confirmed neither by any estimator of a quantitative genetic parameter nor by the correlation between single plant yield and plot yield of their offspring. The disturbing factors found already in the former generation, namely variation in seed quality and a biased sample of random plants, exerted a less important role in the estimation of the progress. Nevertheless, it is believed that only when they can be reduced more reliable results can be achieved.  相似文献   

5.
I. Bos 《Euphytica》1983,32(2):329-335
Summary Up to now the only experiences in favour of the method of honeycomb selection were reported by the spiritual father of the method, i.e., Fasoulas. Three other reports presented very moderate results. Possible causes for these contrasting results are discussed. Fasoulas' preference for growing the plants in the selection field in absence of competition is in conflict with the conditions in commercial crops where intragenotypic competition occurs. This preference is considered in comparison with the more popular preference for growing the plants in the selection field in presence of intergenotypic competition, which in turn also deviates from the conditions in a commercial field. It is suggested that at some degree of interplant competition the highest response to honeycomb selection will be obtained. Further, it is explained why the average of the phenotypic values of the six neighbours of a central plant may be an unreliable measure for the growing conditions for the central plant.  相似文献   

6.
Summary Little information is available on the genetic shifts that may take place when seed mixtures of peanut are grown over time. Five peanut lines with distinct seed coat colors, but similar plant types, pod yields, and maturities, were grown in pure stands for four years. A mixture with equal numbers of seed from each of the five lines was grown each year. All mixtures were subsampled and grown in subsequent years without reconstitution. Yield, 100-seed weight, and total sound mature kernel proportions from the mixtures were higher than the pure stand average of the five lines, but yield and total sound mature kernel proportions were lower than the average adjusted for individual line production. The best component line was significantly better than the mixture for pod yield, 100-seed weight, and proportion of sound mature kernels. Intergenotypic competition shifted the mixture composition to increase the proportion of one of the high yielding lines after only two years, while other high yielding lines in the test either maintained or decreased their original proportion. The two lowest yielding lines in pure stand also decreased in proportion over time.Contribution of the Florida Agricultural Experiment Station. Journal Series No. R-00550.  相似文献   

7.
High concentration of reduced iron (Fe2+) in waterlogged acid soils is a constraint for growing wheat in high rainfall (waterlogged-prone) areas of Western Australia. Growing crop genotypes tolerant to high Fe2+ concentrations may be desirable in such situations, but there is no knowledge about the extent of variability in Fe2+ tolerance in the wheat germplasm. A bioassay for tolerance to high concentrations of iron in wheat was developed and optimised using Siete Cerros (Fe-tolerant) and BH1146 (Fe-intolerant) as control genotypes and a range of FeSO4 concentrations (36, 313, 625, 1250, 1875, 2500 and 3125 μM Fe2+) in nutrient solution in a controlled-temperature environment. Increasing external concentration of iron decreased both shoot and root dry weight, increased shoot iron concentration and intensified the development of toxicity symptoms to a greater degree in intolerant BH1146 as compared to tolerant Siete Cerros. Increased iron supply negatively affected uptake of Ca (r = −0.41) and Mg (r = −0.40). The tolerant genotype Siete Cerros showed an improved avoidance/exclusion of high external concentration of Fe2+ compared with intolerant BH1146. The genotypic discrimination based on relative root dry weight and the development of toxicity symptoms was most pronounced at 625 μM Fe2+. This concentration was chosen for screening of 20 bread wheat and one durum genotype chosen from a preliminary screening of 94 Australian wheat genotypes. A relatively narrow but significant variation (22–38%) in terms of relative root dry weight under Fe2+ toxicity was observed among Australian advanced breeding lines and varieties. The presence of genotypic variation for Fe2+ tolerance across and within the Australian breeding programs could be exploited in a deliberate selection process to enhance Fe2+ tolerance in wheat. Durum wheat (Arrivato) and several Australian wheat varieties and advanced lines in this study were as tolerant to Fe2+ toxicity as Siete Cerros, a variety representing common parentage of iron-tolerant genotypes.  相似文献   

8.
Summary The effectiveness of the honeycomb selection method for yield in spring wheat (Triticum aestivum L.) was evaluated using progenies from two wheat crosses, Glenlea x NB131 and Glenlea x Era. Honeycomb selection was carried out in the F2 and F3 generations, grown at the University of Manitoba in the summers of 1980 and 1981, respectively. In both generations, divergent selection was made for both high and low yield. Plants selected in the F3 generation were entered in an F4 yield test in the summer of 1982. Results of the experiment showed that honeycomb selection for yield in the F2 and F3 generations was effective in identifying parents of high- and low-yielding lines. F3 plants from highyielding F2 selections gave higher yields than those from low-yielding F2 selections by 11.5% and 13.0% for Glenlea x NB131 and Glenlea x Era crosses, respectively. The F4 yield test showed that high yielding selections from both crosses significantly outyielded by 8.9% low yielding selections and by 14.4% the unselected composite lines. It is concluded that the honeycomb selection method can be used for early generation selection in spring wheat.  相似文献   

9.
J. E. Bradshaw 《Euphytica》1986,35(2):433-439
Summary Two experiments were done to evaluate the use of single-row plots for assessing digestible organic-matter (DOM) yield.In the first experiment 29 cultivars were grown in both single-row plots (unguarded) and five-row plots from which only the centre row was harvested (guarded single-row plot). The correlation between yields in the unguarded and guarded plots was very low (r=0.20). Yield was correlated (r=0.89) with cultivar height in the unguarded plots, but not in the guarded plots (r=0.19). Therefore selection for yield in unguarded single-row plots is undesirable and would favour tall kales which are prone to lodging.In the second experiment 16 cultivars were grown in single row-plots guarded by the short cultivar Maris Kestrel, the tall cultivar Vulcan and by the cultivars themselves as control. The correlations between yield in the control plots and yields in the plots guarded with Maris Kestrel and Vulcan were only moderate (r=0.56 and r=0.64 respectively). Therefore the use of a single distinct cultivar to guard single row-plots is undesirable.Selection for DOM yield should therefore be made in multiple-row plots, from which the outer rows are discarded, in order to avoid the undesirable effects of competition.  相似文献   

10.
Summary The HS-family offspring from each of 463 plants occurring in a population of winter rye were grown in a randomized complete block design. According to 4 sets of requirements, 4 groups of HS-families were created. The HS-families belonging to a certain group were considered to be superior with regard to the specified requirements.Independently from this, selection among the 463 parental plants was simulated. The selection was according to 3 methods (truncation selection, grid selection and honeycomb selection) applied with regard to a single plant trait or with regard to two plant traits. Altogether 9 different single-trait and two-trait criteria were studied for each selection method.The quality of some selection procedure or the other, i.e. a combination of a selection method and a selection criterion, was measured on the basis of the frequency of plants giving rise to a superior HS-family among all plants selected by the procedure.It is concluded that grid selection and honeycomb selection are more effective than truncation selection. Further it is tentatively concluded that honeycomb selection is more reliable than grid selection.  相似文献   

11.
M. Mesken 《Euphytica》1987,36(1):129-145
Summary Five cycles of divergent mass selection for crown height in sugar beets gave average gains of 11.3% to 24.1% per cycle. Realised heritabilities were about 0.4. This progress from mass selection was obtained by paying special attention to soil uniformity, seedbed preparation and sowing, regular stands with plant distances of 50 cm, selection per plot, checking of the measurements, equal representation of seed parents in the next generation, reasonable population sizes and flexible selection intensities.Comparing the data of the generations grown in different seasons with the data of the same generations in one growing season resulted in very high correlation coefficients. It is concluded that mass selection can still be a powerful method of intrapopulation improvement.  相似文献   

12.
Summary The plant species Papaver somniferum L. (opium poppy) is grown commercially in several countries under secure area to produce opium and its major alkaloids i.e. morphine, codeine, thebaine, narcotine and papaverine for pharmaceutical industries. In recent years the global demand for these alkaloids and its derivatives are growing. Seeing the global demand there is urgent need to develop high opium yielding varieties integrated with high specific alkaloids. However, a breeding programme focused on developing improved varieties requires knowledge about the genetic variability for the concern traits. Therefore the present investigation was undertaken to examine phenotypic and genotypic variability, broad sense heritability, genetic advance under selection and interrelationship of traits. A total of 122 accessions were found to be highly variables for all the traits studied. Broad sense heritability ranged from 74.18% (for opium yield/plant) to 99.00% (for papaverine content). Expected genetic advance was varied between 33.91% (for morphine content) and 257.46% (for papaverine content). Genetic correlation analysis revealed that opium yield is negatively correlated with morphine and papaverine content. Among alkaloids codeine, thebaine, narcotine and papaverine showed positive correlation among themselves. The correlations among alklaloids were justified based on the biosynthetic pathway of opium alkaloids.  相似文献   

13.
The effect of interplant distance on differentiation and selection a) of the superior lines from a mixture of inbred lines, and b) of individual plants originating from the top lines, was studied in chickpeas (Cicer arietinum L.). For this, 28 chickpea inbred lines were evaluated on a single plant basis in a honeycomb design and in the same field at three interplant distances, for four growing seasons, at Larissa, Greece. The interplant distances were 15 cm (520000plants/ha, strong allo-competition), 30 cm(128630 plants/ha, medium allo-competition) and 100 cm (11500plants/ha, without competition). In addition, the inbred lines were evaluated in replicated plot trials under an agronomically accepted plant stand (520000plants/ha, crop environment) and the ranking of the 28 lines based on the average yield per plot over growing seasons was determined. Selection was applied in each season for each interplant distance and the three and six top lines with the highest average yield per plant were identified. These top lines from each interplant distance were compared with the three and six top lines(say: proven superior lines) identified after their evaluation under crop environment over seasons. In addition, selection was applied at the individual plant level with six selection pressures in each season and each interplant distance. Then we determined for each experiment and selection pressure the number of the selected plants which belonged to the six proven top lines. It was observed that the ranking obtained under crop environment was best correlated with the ranking at the intermediate interplant distance (30 cm), followed by the ranking at the high interplant distance (100 cm). In contrast this correlation was very weak for the ranking at low interplant distance (15 cm).In addition, the interplant distance identifying the highest number of the proven high yielding lines after their evaluation in one season was the intermediate interplant distance followed by the high interplant distance and certainly not the low interplant distance. The relative effectiveness was further increased when selection was based on average performance of the lines across seasons. This, together with the relatively small number of seeds produced per plant, renders selection at low interplant distance less favorable than selection at the intermediate or high interplant distance.The individual plant selection was effective at all three interplant distances. Selection effectiveness generally increased as the selection pressure increased. Again the best results were obtained when selection was applied at intermediate or at high interplant distance. It was concluded that line selection as well as individual plant selection was more effective at intermediate interplant distance and certainly not at low interplant distance. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

14.
Summary Nitrate content was measured in 135 genotypes of cultivated lettuce (Lactuca sativa L.) and 21 genotypes of wildLactuca spp. grown in two experiments. In Experiment 1 plants were grown on nutrient film. In Experiment 2 plants were grown in large pots of potting soil. Within cultivated lettuce five plant types were distinguished and within each of them genotypes were found with low nitrate content. The coefficient of variation in the experiment with plants growing in large pots was not larger than in the experiment with plants growing on nutrient film. In butterhead genotypes nitrate content was negatively correlated with dry matter content and positively with plant fresh weight.  相似文献   

15.
W. Erskine 《Euphytica》1977,26(1):193-202
Summary Six pure lines and four mixtures were grown in six environments throughout lowland Papua New Guinea. There were no significant transgressive increases in the grain yield of mixtures above their pure line components, and mixture yields were adequately predicted by the mean of components. In yield stability it was found that the individual buffering of pure lines was of more importance than population buffering, and that the magnitude of population buffering varied with the particular combination of components. Competitive effects in all the mixtures were of the compensating type. Dramatic changes in mixture composition resulting from natural selection precluded their use in local agriculture. The outcome of competition in mixtures was strongly influenced by the growing environment, such that selective index was correlated to general fertility.  相似文献   

16.
Summary Four six-rowed uniculm lines of spring barley were grown in two yield trials at different sowing densities. One trial was grown on light sandy soil in 1990. The second trial was grown on clay soil in 1991 and included the two-rowed, tillering cultivar Golf. In the trial on sandy soil, the grain yield of the uniculm lines approached that of Golf grown in an adjacent trial, but in 1991 when the growing conditions were more favourable, Golf yielded significantly more than the uniculm lines. Uniculm lines apparently perform relatively better under marginal growing conditions than in high yielding environments.The uniculm lines do not conform to the ideotype proposed for wheat by Donald (1968) but the results show that a drastic change in plant type need not to imply a large drop in grain yield.  相似文献   

17.
Summary With mass selection it is impossible to adjust single plant performance for variation in purely private growing conditions (including instability of development). This was demonstrated by using the character initial kernel weight when honeycomb selection is applied. Further, it was investigated whether reduction for variation for kernel size, depth of sowing and orientation of the kernel at sowing results in reduced phenotypic variation for the mature plant characters on which the selection is based. The conclusion is that with mass selection it is very rewarding to apply a precision drill and to use sieved seed when sowing a selection field. The orientation of the kernel may be neglected.  相似文献   

18.
Competition for water generates a classic aspect of the tragedy of the commons, the ‘race for fish’, where crops must allocate more resource to acquisition of the limiting resource than is optimal for crop yield allocation. A pot experiment using a simple additive (target–neighbour) design was conducted to examine the above‐ground and below‐ground growth of three spring wheat (Triticum aestivum L.) cultivars when grown alone and in mixtures at three levels of water availability. The effects of competition and water availability were compared by observing patterns of growth, biomass allocation and below‐ground outcomes. Competitive interactions were investigated among cultivars ‘HST’, ‘GY602’ and ‘LC8275’, target plant of each cultivar grown without neighbouring plants are referred to herein as control plant and one target plant of each cultivar sown surrounded either by same or another cultivar as intra‐ or inter‐cultivar competition. Competitive ability was assessed as the response ratio (lnRR) between the target plant surrounded by six other plants and the target plant in isolation. Our results showed that the cultivar ‘HST’, released over a century ago, produced a higher biomass and grain yield than the more recently released cultivars ‘LC8275’ and ‘GY602’ when grown as isolated plants with sufficient water supply. However, competition for resources from neighbours led to target plant biomass and grain yield being significantly reduced relative to controls in all three cultivars, particularly in ‘HST’. When subjected to intra‐cultivar competition, the two recently released cultivars ‘LC8275’ and ‘GY602’ had higher grain yields and water use efficiency for grain than ‘HST’ in all three water regimes. The landrace ‘HST’ had better and significantly linear relationships between biomass and biomass allocation, root length and specific root length, whereas the recent and modern cultivars had much more water‐related species‐specific changes in root morphology and allocation patterns. These results suggest that crop traits that influence competitive ability, such as biomass allocation to roots and root plasticity in response to drought have changed in modern wheat cultivars because of breeding and selection.  相似文献   

19.
Summary Yield data from the 5th–12th international mungbean nursery (IMN) trials conducted at 23 sites in 15 countries were analyzed by conventional stability analysis—regression of genotype mean on the environmental index, and by segmented regression analysis—fitting separate linear regressions in low yielding and high yielding environments. The gene pool base concept allows comparison of genotypes from different IMN trials grown in different years and sites. A very high positive linear relationship was observed between the regression coefficient and the average yield of cultivars, indicating that high yielding cultivars were less stable across environments. When data points of the regression of genotype mean and site mean for VC 1973A, a high yielding and widely adapted cultivar, were examined, the relationship appeared not to be linear. The segmented regression analysis improved the coefficient of determination (r2) and the genotypes were grouped based on regression coefficients in high yielding and low yielding environments. Different categories of genotypes suitable for high input environments, widely adaptable genotypes, and highly stable genotypes were identified.Texas Agricultural Experiment Station Technical Article 23208.  相似文献   

20.
Summary Pyrethrum is grown for the insecticides found in the flowers. Due to its perennial habit each selection stage should last three years. Most traits can be adequately observed or measured within one-year cycles. However, it has not previously been investigated whether flower yield, one of the most important traits, could be adequately assessed in one year.Seven replicated yield trials, comprising 110 clones in a similar stage of selection, were observed over a period of three years. The clone effect on flower yield, pyrethrins yield and pyrethrins content were very significant in all trials. The correlation coefficients between the first year's results and the total results averaged +0.91 for flower yield and +0.93 for pyrethrins content. Selection of the highest yielding clones comprising one third of the total number resulted in an increase in pyrethrins yield of 34.3% when selected after the first year and in an increase of 37.5% when selected after three years. This increase was predominantly due to an increase in flower yield, which is caused by the much greater variation for flower yield than for pyrethrins content together with an inverse relation between these two traits.It is therefore possible to select in one-year stages with only a final testing over a 2 to 3 year period.  相似文献   

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