Variation In Yield Components Research Articles

The variation of yield components in wheat (Triticum aestivum L.) in response to stressful growing conditions of alkaline soil

The paper presents the results of experiments with 11 varieties of wheat grown in alkaline soil stressful conditions. The experiment was set up at the site in the Banat, on the non-ameliorated solonetz soil, as control variante, and with ameliorative measures using phosphogypsum. The phenotypic variability and genotype by environment interaction for the grain number and weight per spike, using AMMI model in three vegetation seasons were studied. The analysis of the results revealed that the tested varieties responded differently to external, stressful conditions and ameliorative measures. Based on the AMMI analysis results the significance of PCA axis was observed.

The change of genetic and phenotypic variability of yield components after recurrent selection of maize

This paper deals with 31 SSD lines from ZP-Syn-1 C0 and 37 from ZP-Syn-1 C3 maize populations. After line selection and seed multiplication in the first year of the study, the trials were set during two years in Krusevac and Zemun Polje, in RCB design with three replications. Additive and phenotypic variances of yield components were calculated, as well as the estimation of genetic variability narrowing by multivariate cluster analysis. The differences in additive and phenotypic variances between the cycles were significant for ear length only and highly significant for grain row number per ear and for percent of root and stalk lodged plants. It means, a significant narrowing of additive and phenotypic variance occurred only for those three traits, and the other traits did not change their variability by selection in a significant manner. However, according to cluster analysis, distances among genotypes and groups in the zero selection cycle were approximately double than in the third one, but group definition was better in the third selection cycle. It can suggest indirectly to a total variability narrowing after three cycles of recurrent selection.

Diallel analysis of barley for resistance to leaf stripe and impact of the disease on genetic variability for yield components

Barley breeders in Syria attempting to develop barley (Hordeum vulgare L.) cultivars resistant to barley leaf stripe (BLS) disease caused by Pyrenophora graminea Ito & Kuribayashi [anamorph Drechslera graminea (Rabenh. Ex. Schlech. Shoem.)]. Information on the combining ability for BLS resistance in Syria is not available. This study was conducted to evaluate, in 10 genetically diverse barley parents, general combining ability (GCA) and specific combining ability (SCA) effects towards the determination of the genetic basis of disease resistance and to estimate genetic variability for yield components and its modification by BLS. Ten parental genotypes varying in their reactions to BLS were crossed in a half-diallel mating design to generate 45 full-sib families. The families and the parents were inoculated with P. graminea and evaluated for resistance in replicated field tests (three inoculated and three non-inoculated plots). The parents chosen showed wide variations for resistance to BLS. Genetic component analysis showed significant effects for both GCA and SCA for resistance to BLS, suggesting that additive as well as non-additive genetic mechanisms were involved in the expression of resistance in these parents. GCA effects were more important than SCA effects. Resistant parents exhibited high negative GCA indicating that additive gene effects were more predominant, and suggesting their prime suitability for use in barley breeding programs to improve resistance to BLS. Narrow-sense heritability was 58% and broad-sense heritability was 99% indicating that selection for BLS resistance should be effective in these crosses. A high genetic variability for the agronomic traits studied was observed. Yield components decreased significantly in inoculated plants and more pronounced in diseased plants. Significant GCA was observed for all traits. Values for GCA were, in some cases, significantly modified by BLS. This indicates that attention must be paid to the danger of drawing conclusion in quantitative genetics studies dealing with both diseased and healthy plants. Two genotypes, Banteng and Igri, had high negative GCA effects and are promising parents for enhancement of BLS resistance.

Variability in yield of four grain legume species in a subhumid temperate environment. II. Yield components

The effects of plant population (one-tenth of the optimum to four times the optimum populations in 1998/99 and 10–400 plants/m2 in 1999/2000) and sowing depth (2, 5 and 10 cm) on yield and yield components of four grain-legumes (Cicer arietinum, Lens culinaris, Lupinus angustifolius and Pisum sativum) were studied. Seed yields were strongly positively correlated with the number of pods and seeds/m2 in both years in all species. The mean seed weight and number of branches/plant were inversely related to plant population. There was a nearly six-fold reduction in the number of branches/plant as plant population increased, which was due to restricted branching, and not to branch senescence. Generally, the variation in yield components was species dependent. However, for all species the number of pods/m2 and seeds/m2 could be used as primary criteria for selection in a breeding programme.

Genetic and phenotypic variability of yield components in wheat, Triticum aestivum L.

The heritability, phenotypic variability and components of variance for spike length and number of spikelets per spike have been studied in 50 cultivars from different selection centers all over the world. The experiment was performed in randomized block design in three replications on the experimental field in two years. A total number of 60 plants have been analyzed in the full maturity stage. Average estimated values of spike length and number of spikelets per spike differed significantly among years and among cultivars. The highest average value of spike length had Mironovskaya 808 cultivar (V =14.5 cm), and the lowest value was found in Etoille de Choisy (J=8.1 cm) and San Pastore cultivar (V =8.2). During investigated periods the highest average value for number of spikelets/spike had Sava cultivar (V=28.2), and the lowest value expressed Frontana cultivar (V =19.2). The average variation coefficient for spike length was 8.0%, and for number of spikelets per spike was 7.5%. The lowest variability for spike length was established in Pernel cultivar (V=4.8%) and the highest in Lepenica cultivar (V=12.9%). The coefficient of variation for number of spikelets per spike ranged from 4.7% in Bankut 1205 to 12.4% in Norin 10 cultivar. The obtained heritability values in broad sense were fairly high for spike length (96.4%) and number of spikelets per spike (79.1%). Phenotypic analysis of variance indicated that genetic variance took a larger portion of the total phenotypic variability for spike length (81.82%) and for number of spikelets per spike (57.36%) than influence of environmental factors on expressing of analyzed yield components.

Study of Genetic Variation in Yield Components of Wheat Cultivar Bukhtwar-92 as Induced by Gamma Radiation

Study of Genetic Variation in Yield Components of Wheat Cultivar Bukhtwar-92 as Induced by Gamma Radiation

Effect of fish on the yield and yield components of rice in integrated concurrent rice–fish systems

Many authors report on the effect of rice–fish culture on rice yields. Some reports show increased rice yields, others show no effect or even decreased yields. To verify the impact of rice–fish culture, data gathered over eight experiments (1995–1999) at the Co Do experimental rice–fish station, Vietnam, were analysed through multiple regressions with rice yield and different yield components as the dependent variables. We used eight independent variables: season, water depth, rice variety, rice seeding rate, and the effective stocking density (ESD) of silver barb, Nile tilapia, common carp and snakeskin gourami. Season had the biggest impact on nearly all dependent variables. Rice yields in the wet season were on average 2·42 t/ha lower as compared to the dry season. Higher water levels decreased the number of panicles/m2 and the rice yield. The rice seeding rate affected the yield component variables, but had no impact on the rice yield. Silver barb feeding decreased the number of panicles/m2 but this was compensated by an increased number of grains/panicle. Snakeskin gourami had a positive effect on panicles/m2 and, together with common carp, on sink capacity, probably through improved nutrient cycling in presence of fish and improved nutrient uptake by the rice plant. Snakeskin gourami had a negative effect on the ripening ability, whereas Nile tilapia had a positive effect. Fish did not have any impact on the rice yield. Increased water level and reduced rice arable area, the main two requirements for rice–fish culture, result in lower rice yields from rice–fish systems as compared to monoculture systems.

Site‐Specific Analysis of a Droughted Corn Crop: I. Growth and Grain Yield

Soil in the southeastern USA Coastal Plain exhibits marked variation, especially near shallow depressions called Carolina Bays. This variation causes correspondingly severe variation in yield, particularly for corn (Zea mays L.) during drought. Though important to precision farming, these features often are overlooked in 1:20000 scale county soil surveys. They are visible in 1:1200 scale soil surveys, but the ability to explain yield variation using soil map units at this scale must be unequivocally demonstrated before committing resources to such a detailed survey. Our objectives were (i) to compare paired samples of four soil map units to determine if grain yield variation were sufficiently explained to be of practical value, and (ii) to extend this evaluation to include data with greater spatial coverage. Corn grain yields were measured at 209 sites in an 8‐ha field, including two Carolina Bays near Florence, SC. Site‐specific effects of soil variation on crop phenology, biomass, and yield components were measured at 11 sites during a drought. Variations in yield components were large and sometimes compensatory (e.g., kernel number and mass), with distinctly different routes to sometimes similar final grain yields. Multiple sites within map units were frequently different at α = 0.05. Analysis of variance for grain yield on soil map unit was statistically significant (P < 0.001) but of limited explanatory value (r2 = 0.16). We conclude that to create soil management zones for precision farming, one must augment even detailed soil map units with additional spatial data, such as yield maps.

Variabilidade genética para peso de grão e número deespiguetas por panícula em Avena sativa l. e Avena fatua l.

O incremento no rendimento de grãos tem sido uma das principais metas dos programas de melhoramento da aveia. A busca de variabilidade genética para componentes do rendimento é considerada uma estratégia de melhoria no potencial de rendimento de grãos. O presente trabalho foi realizado com o objetivo de identificar variabilidade genética para os caracteres morfofisiológicos peso de grão e número de espiguetas por panícula em genótipos de aveia cultivada (Avena sativa L.), introduções silvestres de Avena fatua L. e populações híbridas naturais de A. sativa L. x A. fatua L. Ampla variabilidade genética foi detectada entre e dentro dos grupos, para os caracteres avaliados. Os genótipos do grupo cultivado (Avena sativa L.) revelaram peso de grão superior e pequeno número de espiguetas por panícula. As introduções silvestres de A. fatua L. apresentaram reduzido peso de grão e baixo número de espiguetas por panícula. Entretanto, algumas populações híbridas da geração F2 revelaram alto peso de grão e baixo número de espiguetas por panícula, passíveis de serem utilizadas no programa de melhoramento.

Effects of soil water deficit at different growth stages on rice growth and yield under upland conditions. 2. Phenology, biomass production and yield

Phenological development, shoot dry matter production, grain yield and yield components of rice were examined in relation to drought occurring at various stages of growth. Rice was sown three or four times at three-week intervals in the field in each of two years, and performance in three stress trials was compared with that in corresponding irrigation trials, with the aim of quantifying the response of the crop to water stress of 23–34 days' duration developing at different growth stages. When drought occurred during vegetative stages, it had only a small effect on subsequent development and grain yield. The reduction in yield of up to 30% was due to reduced panicle number per unit area in one trial, and reduced number of spikelets per panicle in another. The effect of water stress on yield was most severe when drought occurred during panicle development. Anthesis was delayed, the number of spikelets per panicle was reduced to 60% of the irrigated control and the percentage of filled grains decreased in one crop to zero. This decrease in grain yield to less than 20% of the control was associated with low dry matter production during the drought period as well as during the recovery period following the drought. When drought occurred during grain filling, the percentage of filled grains decreased to 40% and individual grain mass decreased by 20%. The effect of stress was also related to its severity during grain filling. Stress at this stage hastened maturity. The results suggest that variation in yield components due to water availability is related to the variation in dry matter production at particular growth stages. Results of a supplementary shading experiment show that the relationship between spikelet number per panicle or single grain mass and crop growth rate was the same, whether growth rate was varied by availability of soil water or solar radiation. Filled-grain percentage, however, was more sensitive to drought stress than shading when comparison was made at a similar crop growth rate.

Dynamics of Competition in Populations of Carrot ( Daucus carota)

Populations of carrot ( Daucus carota) were raised over a wide range of densities (79–5763 plants m -2) to examine the dynamics of competition in terms of yield–density relationships and size variability, and to investigate the effects of nutrient supply on competition. While the relationship between shoot yield and density was asymptotic, the relationship between root and total yield and density tended to be parabolic. For a given time and density series the relationship between yield per unit area and density could best be described by the model: y=w mD (1+aD) b where yis the yield per unit area, Dis density, w m, a and bare fitted parameters. The parameters w m and aincreased over time but nutrient availability affected only w m. An extension of the basic yield-density model is proposed to describe the dynamics of the yield–density relationship over time: y=kD [1+cexp(-rt)]{1+α[k/ (1+cexp(-rt))] b D} b in which tis time, k, c, r, α and β are fitted parameters, and the other parameters are as previously defined. Size variability of individuals, measured by the coefficient of variation (CV), was influenced by both density and time after sowing. The general relationship between CV and the logarithm of mean weight per plant, after first harvest, could be described by a linear regression model, with a slope of approximately -0.2. A theoretical justification for a monotonically declining relationship between CV and mean plant weight is proposed. The magnitude of size variability was ranked in the order: root weight>total weight>shoot weight. The differences in the magnitude of size variability in yield components were due in part to allometric growth of plant parts. Nutrient availability, however, had no influence on size variability.

Available Water and Nitrogen Effects on Yield Components and Grain Nitrogen of Zero‐Till Spring Wheat

AbstractStraw yield is important in soil conservation and nutrient cycling. Grain N concentration is of economic importance, and variations in yield components can be used to improve our understanding of grain yield response to environmental stimuli. Therefore, quantifying these responses in relation to soil water and N fertility is of considerable importance. A 9‐yr study was conducted in southwestern Saskatchewan on a medium textured Aridic Haploboroll using zero‐tillage management. We examined the influence of snow trapping and fertilizer management (rate, placement, and time of N application) on hard red spring wheat (Triticum aestivum L.) grown annually. Multiple regression was used with backward elimination to relate straw yield, heads per plant, kernel weight, and grain N concentration to available water use (WU), fall soil NO3−N in 0‐0.6 m depth (SN), rate of urea fertilizer N (FN), years of consecutive cropping (Yr) and several interactions among these variables. Significant (P < 0.0001) meaningful relationships were obtained betwen straw yield (R2 = 0.78, P = 0.001), kernel wt (R2 = 0.81, P = 0.001), heads/plant (R2 = 0.36; P = 0.001) and grain N concentration (R2 = 0.56, P = 0.001) and the independent variables. In this semi‐arid region, WU was by far the most important factor influencing all characteristics. The effect of SN was often more important than that of FN. Further, the advantage of SN over FN increased with years of cropping, possibly reflecting a gradual increase in the N supplying power of this well‐managed soil. Straw yield was related to grain yield. The relationship expressed in kilograms per hectare, was SY = 285 + 0.77 GY + 0.00029 GY2, R2 = 0.85, P = 0.001, n = 1248). Grain N concentration was greater for spring than for fall‐applied N in 5 of 9 yr, and deep banding superior to broadcasting in 1 of 9 yr.

Yield Component Analysis of Strawberry Genotypes Differing in Productivity

Abstract Strawberry genotypes (Fragaria × ananassa Duchesne) varying in yield per plant were studied. In 1985, genotypes were grown in matted rows and in 1986 as individual plants. Yield per plant within genotypes was mainly dependent on the number of berries per plant, regardless of cultural system. Other variables were correlated with yield, including crown dry weight and leaf area after harvest, and number of inflorescences, which indirectly affected berry number. Potential differences in yield within genotypes apparently were established prior to flower bud differentiation. Variables associated with yield among genotypes differed with cultural conditions. When genotypes were grown in matted rows, vegetative variables were highly correlated with yield. With less interplant competition, reproductive variables were correlated with yield among genotypes. Data suggested that, in some genotypes, runnering and fruiting may have competed for assimilates. Genotypic variability in yield components suggests that genotypes with similar yield can have different routes to yield.

Cultivar Variation in Yield Components of Strawberries

Abstract Differences were observed both within and between strawberry cultivars in the relative importance of yield components. Most cultivars had high coefficients among yield, crown density at harvest, and fruit number/crown, but there was variation among cultivars in the coefficients between yield and fruit weight.

Hybrid Vigor and Combining Ability in a High‐Low Yielding, Eight‐Parent Diallel Cross of Soft Red Winter Wheat1

A high‐low, eight‐parent diallel cross of soft red winter wheats (Triticum aestivum L. em. Thell.) was grown in hills to study hybrid vigor and combining ability for three components of grain yield and grain yield, using moderately diverse parents which varied in yielding ability. Diversity was based on plant type and parentages of the eight cultivars and lines. All were adapted for production in Indiana. Four parents were low in yield and four were high. This design provided 6 hybrids from low × low crosses, 16 from low × high, and 6 from high × high.Hybrids with grain yields which were significantly above that of the higher parent occurred infrequently, but such hybrids did occur in each crossing group. Heterosis above the midparental value was about 30% for low × low crosses, 25% for low × high crosses, and 19% for high × high crosses. Hybrid vigor for yield in low × high crosses was not significantly different from that in like by like crossing groups.The preponderance of the variability for yield components and grain yield was attributed to general combining ability. Successful hybrid wheats will most often come from high × high crosses because of the preponderance of general combining ability effects in wheat.

Genotypic and environmental variation in crop yield. A method of estimating the interdependence of the components of yield

Because yield components do not behave as independent attributes the conclusions derived from simple yield analyses are of limited value in plant breeding programmes. By calculating a function W of the variances and covariances of the yield components, it is possible to estimate, on a scale from 0 to 1, the degree to which the variations in yield components were independent of one another in any given experiment. By this approach examples of almost complete compensation among the components (W = 0), of mutual independence of the components (W = 0.5), and of additivity of the components (W = 1.0) have been discovered in original data and in the literature. Reasons, and possible applications for these findings are discussed. Investigations into the sampling properties of W are reported in an appendix.

Yields and components of yield of dry beans (Phaseolus Vulgaris L.) in the United Kingdom

SummaryExotic accessions of Phaseolus vulgaris selected for seedling cold tolerance by Austin & Maclean (1972) in a test in controlled environments were grown in a field experiment at Wellesbourne in 1974. Yields of up to 4·;7 t/ha at a plant density of 34 plants/m2 were obtained. In 1975, six selected accessions were grown at 21 plants/m2 at six different sites. Mean site yields ranged from 1·0 to 3·1 t/ha. The six accessions all had better emergence and higher yields than two commercial cultivars used as controls. The genotype × site interactions for yield (and for yield components) were small. The variation in yield between accessions (from 2·0 to 2·5 t/ha) was smaller than the variation in yield between sites. Variation in yield components tended to be additive between sites, and compensatory between accessions. There was a negative correlation between crude protein content and yield across accessions; the correlation between protein content and yield across sites was not significant. Accessions differed significantly in the amount of green leaf still attached to plants at harvest. This variation was not related to maturity as judged by moisture content of the seed. There was a negative correlation across accessions between the weight of leaf per plant at harvest and harvest index (the ratio of seed weight to stem weight).

Heterosis and Variation of Yield Components in F1 Hybrids Between Group Tuberosum and Group Andigena Potatoes1

Five clones of Solanum tuberosum L. Group Tuberosum (T) and five long‐day adapted clones of Group Andigena (A) were crossed to produce four populations (TT, AA, TA and AT) in such a way that there was selling in the intra‐Group crosses. The populations were grown for 2 years as spaced plants in a randomized, complete‐block design and compared for plant vigor, maturity, tuber number, mean tuber weight, and total yield to evaluate the potential of the inter‐Group hybrid (TA and AT) populations in broadening the genetic base of potato cultivar development. In four comparisons, the TA and AT populations outyielded the TT population by 8.6 to 32.9%. Also, the TA and AT populations generally had larger variance estimates for total yield. It is concluded from the analysis of population means for tuber number, mean tuber weight, and total yield that in the TA and AT populations the heterosis for total yield results largely from the multiplicative interaction of the two yield components. The TA and AT populations showed no consistent reciprocal differences. The TA and AT populations showed greater stability than the TT population. These results have important implications for potato breeding.

Study of Variation in Yield Components of Rice Varieties

A correct estimation of yield components and its role are of invaluable help to the breeder to eliminate much of his difficulties and uncertainties in the early stage of selection of the breeding material. Much work has been done on the components affecting grain yield in rice and definite correlation have been established. The varieties possessing similar yielding capacity, however, differ widely, in their other characters. Often the breeder is confronted with the problem of synchronising this variation with their total effect on yield. Here, an attempt has been made to assess the range of variation in yield components and their interdependence.