共查询到20条相似文献，搜索用时 31 毫秒
1.
Kenneth A. Gravois 《Euphytica》1998,101(2):151-156
High rough rice yields are important for the profitable production of rice (Oryza sativa L.). The value of rough rice is determined
primarily by head rice (whole milled grains) and broken rice, together referred to as total milled rice. The objective of
this study was to optimize selection for rough rice yield, head rice, and total milled rice using path-coefficient analysis
and selection indices. Thirty-seven long grain pure lines were grown in an experiment at three Arkansas locations during 1993
and 1994. In another test, twenty-eight F1 hybrids obtained from an eight-parent half diallel of long-grain rices were grown at two locations in Arkansas during 1991.
For the pure lines, path analysis revealed that rough rice yield was approximately twice as important in determining total
milled rice/ha than head rice. Path analysis for the hybrids revealed that rough rice yield was an even greater component
in determining total milled rice/ha. Based on yield components for hybrid rice, panicle density had the largest direct effect
determining total milled rice/ha. Filled grain/panicle, grain weight, and head rice, in that order, were secondary, but positive,
factors determining total milled rice/ha. A selection index for pure lines based only on selection for head rice was 19.2
percent as effective as selection for total milled rice/ha directly. When selection for total milled rice/ha was based solely
on rough rice yield, selection was 82.7 percent as effective as selecting for total milled rice/ha directly. Selection to
improve total milled rice/ha should concentrate on increasing both rough rice yield and head rice. Rough rice yield should
receive greater priority than head rice in selection strategies.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
Summary Data of planting and plant density are two cultural practices influencing grain yield of maize (Zea mays L.). Our study was designed to evaluate the usefulness of a mass selection scheme to improve cold and density tolerance of the BS2 and BS3 maize populations. Populations were planted at an early planting date and a high plant density, and three cycles of mass selection for well-filled ears on erect plants were conducted at earch of three Corn Belt locations (i.e., Waseca, MN; Ames, IA; Portageville, MO).Results showed that selection improved cold tolerance traits of BS3, but not of BS2. Mass selection did not increase density tolerance of either population at any location. Selection did not improve response to planting dates, although the early planting date did improve agronomic performance and grain yield of all entries. We concluded that mass selection at high plant densities and early planting dates at diverse geographical locations did not produce cycles adapted to specific environmental conditions. 相似文献
3.
Rice improvement is based to an increasing extent on ever-sharper genetic analysis to the detriment of classical breeding,
which is disappearing. Analytical genetics are very promising, but they cannot replace integrated and finalized breeding.
Little attention has been paid to improving participatory rice breeding methods for subsequent integration into sustainable
cropping systems. Special methodological initiatives are required to ensure the success of this breeding-agronomy integration.
This integration of inexpensive breeding methods has increased the biodiversity of rice: low temperature and drought tolerant
upland rice varieties for mountain areas, and polyvalent varieties, which have the ability to grow in both rainfed or irrigated
conditions, they are perfectly adapted to improved cropping systems and to beneficiaries’ needs and preferences. These preliminary
results on this integration demonstrate that the present approach is relevant. 相似文献
4.
5.
Junghyun Shim Gideon Torollo Rosalyn B. Angeles-Shim Rogelio C. Cabunagan Il-Ryong Choi Un-Sang Yeo Woon-Goo Ha 《Breeding Science》2015,65(4):345-351
Rice tungro disease (RTD) is one of the destructive and prevalent diseases in the tropical region. RTD is caused by Rice tungro spherical virus (RTSV) and Rice tungro bacilliform virus. Cultivation of japonica rice (Oryza sativa L. ssp japonica) in tropical Asia has often been restricted because most japonica cultivars are sensitive to short photoperiod, which is characteristic of tropical conditions. Japonica1, a rice variety bred for tropical conditions, is photoperiod-insensitive, has a high yield potential, but is susceptible to RTD and has poor grain quality. To transfer RTD resistance into Japonica1, we made two backcrosses (BC) and 8 three-way crosses (3-WC) among Japonica1 and RTSV-resistant cultivars. Among 8,876 BC1F2 and 3-WCF2 plants, 342 were selected for photoperiod-insensitivity and good grain quality. Photoperiod-insensitive progenies were evaluated for RTSV resistance by a bioassay and marker-assisted selection (MAS), and 22 BC1F7 and 3-WCF7 lines were selected based on the results of an observational yield trial. The results demonstrated that conventional selection for photoperiod-insensitivity and MAS for RTSV resistance can greatly facilitate the development of japonica rice that is suitable for cultivation in tropical Asia. 相似文献
6.
Natália Botega Alves Marcio Balestre João Paulo Pennacchi Monique Caroline Nunes Fernandes Douglas Goulart Castro Flávia Barbosa Silva Botelho 《Plant Breeding》2020,139(5):853-861
The rice crop is affected by diseases throughout its cycle, impacting negatively on grain yield and quality. The control of the disease impact can be accomplished via crop breeding, using highly multiple resistant genotypes. This study aimed to evaluate the efficiency of multiple-character and specific selection of multiple resistance to major culture-associated diseases (neck blast, leaf scald and grain discoloration) in rice lines of the Upland Rice Genetic Breeding Program. The experiments were conducted in 35 sites during 12 agricultural years, where 124 lines were evaluated for the severity of fungal diseases, under natural field conditions. Multiple parameters were calculated based on the diseases´ scores: genetic, phenotypic and environmental variances, heritability, selection gain, renewal rate, and genetic and renewal progress. Genetic variance for the disease resistance was identified in the population, and the selection gain for multiple-character selection was of 3.16 year−1 throughout the breeding process with a renewal rate of over 35%. The programme has showed efficiency in selecting multiple resistant genotypes to the mentioned diseases, highlighting genotypes with high potential for market release. 相似文献
7.
Summary Alternative strategies of multi-site testing of advanced lines in the northern wheat belt of New South Wales have been evaluated, using genetic parameters for large plot grain yield and hill plot harvest index estimated from dryland and irrigated trials at regional sites during 1975–1981. The average pairwise genetic correlation of large plot grain yields recorded at different sites within years was 0.45±.03, with a mean repeatability within trials of 0.56±.05. Harvest index measured in 20-grain hill plots in 1978 showe genetic correlations of 0.98±.08 with plot yield at the same site, and 0.39±0.06 with plot yield assessed at other sites in the same year.The genetic correlation between harvest index in hill plots and total biological yield in large plots at the same site was 0.84±.13, the relationship showing no evidence of curvilinearity. Selection for harvest index in hill plots is therefore expected to lead to an increase in biological yield as well as grain yield in the breeding populations studied. Quantitative genetic theory suggests that the response to selection for grain yield can be increased by approximately 40% with an initial screening using hill plot harvest index at three sites instead of one, and reallocation of resources in the first stage of large plot yield assessment to include 6–8 sites, rather than dryland and irrigated trials at a single location. 相似文献
8.
R. W. van den Bulk 《Euphytica》1991,56(3):269-285
Summary Somaclonal variation, i.e. the variation induced by cell and tissue culture, offers an opportunity to broaden the genetic variation of crops. As a result of somaclonal variation a wide range of plant characteristics can be altered. However, the selection of agronomically important traits, e.g. disease resistance, has many limitations. The efficiency of selection can be increased by the application of in vitro selection procedures. Selection strategies that may be applied to obtain disease resistant somaclonal variants are described. Their merits and limitations, in relation to the efficiency of the procedures, the frequency of disease resistant variants and the genetics of the resistance obtained, are discussed. 相似文献
9.
Although increase in rice (Oryza spp.) production is a common objective for rice-producing countries in sub-Saharan Africa (SSA), basic information on yield and its variation at farm level is lacking. Field surveys were conducted in irrigated lowland (IL), rainfed lowland (RL), and rainfed upland (RU) rice production systems in 19 SSA countries in the 2012–2014 wet seasons. Mean yield varied widely across sites: 2.2–5.8 t/ha, 1.1–5.2 t/ha, and 1.0–2.5 t/ha in IL, RL, and RU, respectively. Rice yield levels differed between the agro-ecological zones (AEZs) with the highest yield in the semi-arid zone in IL, and in the highlands zone for RL and RU. Cluster analysis identified four groups using mean yields, coefficient of variation, and skewness of yield distribution of 42 site–production system combinations. Grouping was related to production system, AEZ, and field water condition. A high-yielding group with 5.3 t/ha mean yield and negative skewness had only four site–production system combinations. Other groups had mean yields from 1.6 to 3.5 t/ha with positive skewness. In these groups, research and development priority for lifting rice yield could be given to low-yielding IL and RL sites with large yield gaps. Raising rice yield in the humid zone irrespective of the production systems and RU across AEZs remain major challenges. Further assessment of the impact of farmers’ agricultural practices on yield variation is warranted to identify potential interventions to realize further yield enhancement. 相似文献
10.
The success of a new variety of Arabica coffee (Coffea arabica L.) depends to an important extent on its liquor and bean qualities. Selection for these traits is however constrained by
the prevalence of large genotype-by-environment (G×E)interactions in conjunction with the low genetic variability characteristic
of this species. The aim of this study was to assess the extent to which key bean and liquor traits are affected by the environments
and could be combined in order to improve the efficiency of selection for coffee quality in a narrow genetic basis set of
hybrids obtained from a set of related lines and collectively representing the Ruiru 11 cultivar. Twenty-one full-sib families
representative of this hybrid cultivar grown in Kenya in five sites exhibiting strong edaphic and climatic differences were
used for the study. Rainfall amounts during various phases of berry development were used to explain the differences observed
in the discriminating abilities of the locations for bean and liquor traits. The results showed that these families were best
differentiated for bean sizes in the site where moisture supply was optimal throughout berry expansion and filling stages,
whereas discrimination on the basis of liquor traits were best observed in the site where moderate moisture stress occurred
during bean filling stage. The overall precision in prediction of family values was low for liquor qualities; but a much more
efficient selection for large bold beans, optimally based on the AA grade was shown to be possible. Selection indices for
family selection were computed to realize a trade-off between genetic gains in bean size and liquor flavour.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
11.
Selection for biomass yield in wheat 总被引：2，自引：0，他引：2
R. C. Sharma 《Euphytica》1993,70(1-2):35-42
Summary Biomass (above ground plant parts) yield may be a useful selection trait for yield improvement in wheat (Triticum aestivum L.). This study was conducted to estimate realized heritability of biomass yield and to determine the response to selection for high and low biomass yield in 8 genetically diverse populations of spring wheat under two production systems. Selections were made among the F3 lines. Progenies of the selected lines were evaluated in replicated field tests in the F4 generation under high fertility and low fertility production systems at Rampur, Nepal, in 1991. Fertility level had a significant effect on biomass yield, grain yield, effective tiller number, number of kernels per spike, thousand kernel weight, and harvest index. Selection in the F3 for high and low biomass yield was effective in identifying F4 lines with high and low biomass yield, respectively. Biomass yield differences between high and low selection groups in the F4 generation, expressed as percent of the mean of the low selection group and averaged over the eight populations, were 53.9 and 36.5% higher than the mean of the low selection group under the high and the low fertility production systems, respectively. The corresponding figures for grain yield were 48.8 and 34.9% under the high and the low production systems, respectively. Also, selection for high biomass yield resulted in higher effective tiller number, and number of kernels per spike, but lower harvest index. Realized heritability estimates for biomass yield were greater at high fertility (range 0.49 to 0.85) than at low fertility (range 0.22 to 0.44). Biomass yield showed positive genotypic correlations with grain yield, effective tiller number, and number of kernels per spike but a negative correlation with harvest index. The results indicated that selection for high biomass yield should bring about positive improvements in biomass yield, grain yield, effective tiller number, and number of kernels per spike. The correlation between F3 and F4 generations suggested that biomass yield in the F3 generation was a good predictor of biomass yield and grain yield in the F4 generation. Selection for biomass yield in wheat should be made under the standard production system to obtain a realistic response. 相似文献
12.
Summary Aspects of selection for yield and harvest index were investigated by simulating selection using data from random pedigreed F2, F3, F4 and F5 derived lines from two crosses grown in plots at two sites over two years.Improvement in yield through selection was obtained when the response was measured at the same site and in the same year as the selection. Selecting the best 10 per cent of F2 to F4 derived lines gave F5 derived lines that outyielded random selections by 19 to 53 per cent for one cross and 5 to 23 per cent for the second cross. These lines were 41 to 50 per cent better than the mid-parent in one cross, but were less than the mid-parent in the other cross.However, the response to selection when measured in a different year was little better than random selection. The effect of different sites also reduced the effectiveness of selection.Selection of harvest index in early generations for improvement of yield was ineffective when response was measured at the same site in the same year, or in different years.Contrary to some theoretical proposals, the same improvement in yield was obtained by selecting in early or late generations. While high yielding genotypes may be lost by delaying selection, this is counteracted by the better predictive value of late generations due to their greater homozygosity and homogeneity. 相似文献
13.
Improvement of maize populations for resistance to downy mildew 总被引：1，自引：0，他引：1
Upgrading levels of disease resistance are a primary objective of maize breeding programmes. Efficacy of S1 recurrent selection in improving levels of resistance to downy mildew (DM) infection was assessed in Nigeria from 1997 to 2000 in six maize populations. Improvement procedures consisted of evaluating S1 progenies under artificial infection with DM spores and in disease‐free environments and using a selection index to combine selection for reduced DM infection with appropriate agronomic characters from more than one environment. Three to four cycles of selection were completed in each of the populations. Products from the different cycles of selection were evaluated and data collected on DM infection parameters and agronomic traits. Result obtained showed 3–4 cycles of selection were adequate to reduce DM infection levels significantly and increase grain yield. Downy mildew infection decreased by between 58 and 100% while grain yield increases ranged from 10 to 98% for the 2‐4 cycles of selection relative to the C0 (original). Selection increased grain yield with acceptable changes in plant height while maintaining maturity in disease‐free environments. 相似文献
14.
R. A. Richards 《Euphytica》1978,27(2):609-615
Summary Expectations of yield improvement in environments where drought was the major environmental factor limiting yields were studied in two species of rapeseed. Selection for yield in a drought stressed environment was predicted to be a more efficient selection stategy for yield improvement in dryland situations than selection in a more optimal environment, or selection based on a drought response index. The results indicate that selection for yield in a stressed environment are expected to lead to genetic advances in yield under optimal conditions as well as in a drought index. Selection under well watered conditions, on the other hand, was also expected to lead to correlated increases in yield in droughted environments but to decreases in the drought index. These results were found in both species of rapeseed grown in different water stress situations.The genetic advance in a drought response index was predicted to be greater in B. napus and marginally less in B. campestris if selection was practised for yield in a stressed environment rather than direct selection for the drought index. This was due to the higher heritability estimates in the stressed environments and the positive genetic correlations with yield. 相似文献
15.
Understanding the association among wheat growing locations allows plant breeders to better target crosses and identifies locations for germplasm exchange. To examine the relationship between yield testing sites in eight countries in western/central Asia, 291 data sets from CIMMYT's different international yield nurseries were combined into one analysis as no single nursery was well represented across the region; these nurseries represented wheat germplasm specifically developed for different agro-ecological zones including irrigated, semi-arid, high-rainfall, autumn- and spring-sown conditions. The shifted multiplicative model was used to group individual sites into clusters. Results revealed 18 site-by-site combinations as 'similar' to each other and 23 as 'contrasting' at a probability level of P < 15%. CIMMYT's main yield testing site in northern Mexico proved the best predictor for the region. Within the region two sites in Turkey and Iran were identified as possible sites for future regional testing. Overall the study showed that data from different yield nurseries can be combined to improve our understanding of site associations across western/central Asia to the benefit of both international and regional wheat breeders. 相似文献
16.
S. Ceccarelli S. Grando E. Bailey A. Amri M. El-Felah F. Nassif S. Rezgui A. Yahyaoui 《Euphytica》2001,122(3):521-536
The paper describes experiments on farmer participation in plant breeding conducted in three countries (Morocco, Syria and
Tunisia) on barley, which is the predominant annual rainfed crop in the most marginal areas of these countries. Trials with
different types and number of breeding material were planted both on research stations and in farmers' fields. Selection was
done by professional breeders and farmers and data were gathered on breeders' and farmers' selection criteria and selection
efficiency. The trials reflected the situation of the crop in the three countries, with high yields on station, low yields
in some of the most marginal farmers' fields, and poor correlations between research stations and farmers' fields, as well
as between farmers' fields. Grain yield was by far the most commonly used selection criterion by the farmers. However, farmers
also made a widespread use of selection criteria not normally used by breeders such as grain filling and straw yield, as well
as other characteristics of the straw (color) and of the leaves because of the importance of the crop as source of animal
feed. A major difference between the selection criteria used by breeders and farmers was disease resistance, almost entirely
neglected by the latter. Farmer selection was effective in identifying some of the highest yielding lines in the farmers'
own fields and also in those cases where they performed selection on station. The coincidence between entries selected by
the breeder and the farmers was high in Morocco but very low in Syria and Tunisia. There were substantial differences between
the lines selected by the breeders on station and those selected by farmers in their fields. In Syria, decentralized-participatory
selection was significantly more efficient in identifying the highest yielding entries in farmers' fields than any other selection
strategy. This work demonstrates that it is possible to organize a plant breeding program so that farmers become major actors
in the selection of new cultivars.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
17.
Summary The costs associated with yield testing cause maize (Zea mays L.) breeders to search for ways to maximize testing efficiency. The objective of this study was to select individual locations, or a group of locations as preliminary testing sites for yield evaluation of maize hybrids within FAO 600 maturity zone in Yugoslavia. Yield data for 12 locations obtained for the period 1975 to 1984 were used. The predictive potential of the site was judged by the correlations between location means and overall mean (r>0.95), linear regression of locations means on overall mean (b>1.0) and percentage of the 10% overall highest yielding hybrids selected by 10% selection intensity at each location, or at the group of locations (Is>80%). Also factors as average location yield (x) and variation in individual location yield during the period of 10 years (CV) were related to the predictive potential of the site. Differences among locations in all criteria were found. Average yielding locations had higher values of estimators of predictive ability of overall performance than low yielding locations. None of individual locations satisfied all requested criteria. Five locations with highest values for each individual criterion were selected and all possible two, three, four and five-location combinations among them studied. Combinations of two locations could be used for very preliminary screening of hybrids by applying mild selection intensity. A more accurate prediction of overall one-year performance requires an evaluation of hybrids in a minimum of three, but frequently four, selected locations. However, for precise estimation of over-year hybrid performance, testing the hybrids at selected locations in more than one year is necessary. 相似文献
18.
Summary A population of 572 F2 derived F3 lines from six crosses were used to estimate parameters relevant to selection for resistance to Septoria nodorum of wheat. Lines were grown in disease free (fungicide sprayed) and inoculated microplots in 2 replications of a split-plot design in a single environment in 1977. Average yield reduction due to disease was approximately 50%; this was associated with an average septoria score of 50% on the flag leaf, an average septoria score of 42% on the head, and a reduction of 37% in seed weight. Low S. nodorum scores were correlated with late heading date, tall plant height, high grain yield, and high seed weight in diseased plots, and high seed weight % (seed weight in diseased plots expressed as a percentage of seed weight in fungicide sprayed plots).Restricted selection indexes were used to study the relative contributions of disease escape, true resistance, and tolerance to variability in grain yield in diseased plots, seed weight in diseased plots, and seed weight %. True resistance appeared to be the most important factor causing variation in grain yield in diseased plots and seed weight %. Tolerance and escape seemed to be more important for seed weight in diseased plots.Heritabilities of S. nodorum scores on the flag leaf and head were 63% and 52%, respectively. Leaf and head scores could be used most effectively as selection criteria to upgrade resistance in a population before harvest.Selection for high seed weight % slightly reduced yields in disease free plots, although yield in diseased plots and seed weight in diseased plots were increased. However, selection for increased yield or increased seed weight in diseased plots improved yield in disease free plots. It is suggested that direct selection for yield or seed weight in diseased plots is likely to achieve more desirable goals than selection for seed weight %. 相似文献
19.
A recurrent selection program for adaptation to diverse environments was successful in improving mean oat (Avena sativa L.) grain yield within and across testing environments. The objectives of this research were to determine if this selection
program also resulted in changes in other agronomic traits or altered yield stability. Additionally, we investigated how selection
modified the response of genotypes to climatic conditions. We evaluated random samples of 100 families from the original population
and each of three selection cycle populations in replicated yield trials in Idaho, Iowa, and Norway for two years. Yield stability
was assessed via joint regression analysis and superiority analysis. For each cycle, genetic relationships among yields observed
indifferent environments were assessed by estimating phenotypic correlations between pairs of target environments. The effect
of climate variables on genotype-by-environment interaction (GEI) responses was determined with partial least squares regression.
Selection resulted in a small increase in mean heading date, a decrease in mean test weight, and no change in total above-ground
biomass or plant height. Genotypic regression coefficients on environmental indices and deviations from regression were larger
in the last cycle population, but superiority analysis demonstrated that selection significantly improved the adaptability
of the population to the target testing environments. Improved adaptation was also demonstrated by increased phenotypic correlations
among the most divergent pairs of environments in the later cycles. Partial least squares regression of GEI effects on climate
variables suggested that later cycle families tended to respond more favorably to cooler than average conditions than the
original population. Selection resulted in improved yield stability as well as improved mean yield.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
20.
Selection for brown stripe downy mildew resistance in maize 总被引：3，自引：0，他引：3
Summary The maize (Zea mays L.) cultivar Makki Safed 1 (MS1) with susceptibility to brown stripe downy mildew (BSDM) caused by Sclerophthora rayssiae var. zeae
Payak & Renfro, was subjected to two cycles of mass selection and one cycle of full-sib family selection. Selection was carried out primarily for BSDM resistance.The mass selection was practised under artificial epiphytotic conditions in a disease nursery. Full-sib progenies and performance trials on MS1 and its improved versions were grown in diseased and disease free environments.Mass selection resulted in a significant improvement for resistance to BSDM. A cycle of full-sib selection resulted in an additional improvement for resistance to the disease. The disease rating of the improved version was 1.5 against 4.5 for the original population (scale: 1, highly resistant to 5, highly susceptible). The yield of the improved populations of MS1 was significantly greater than that of MS1 in the disease nursery. In disease free experiments, the improved populations showed almost no yield advantage over MS1. There were also no significant differences between the original population and the improved population after three selection cycles for ear length, ear girth, number of kernel rows per ear, number of kernels per row, 1000-kernel weight, plant height, ear height and days to silk. 相似文献