Selection of test locations for regional trials of barley

Summary Three sets of regional six-row barley (Hordeum vulgare L.) trial data, representing cultivar x location x year, were grouped for locations based on the similarity of genotype x environment (GE) interaction. Locations were selected from each group (cluster) so that the structure of the GE interaction generated by the subsets of the locations would be approximately similar to that of the whole set (all locations). The purpose of this paper is to determine the number of locations where the GE interaction structure generated by these selected locations would be fairly consistent over years. Two statistics were used to measure the success of the selected locations: (1) the ratio of GE mean square (MS) associated with the selected location set relative to that associated with the best set (which gives the highest GE interaction MS) and (2) the rank correlation between the cultivar means averaged over the selected locations and those based on the entire data set. The results show that, for eastern Canada, 10–13 locations based on the cluster method can achieve a fairly consistent GE interaction structure over years.Contribution no. R-078 from Research Program Service, Agriculture Canada, and contribution no. 1352 from Plant Research Centre, Central Experimental Farm     

作物品种区域试验试点区辨力评价方法的比较(英文)

试点区辨力是作物品种区域试验试点选择的重要依据,可以用不同的方法进行评价。本研究分别对西南玉米区域试验2003和2004两年的产量数据进行联合方差分析,然后用变异系数(CV)、遗传变异系数(GCV)、环境区分指数(DI)、B型生态价(WE)、回归系数(RC)、基于AM MI分析结果的试点互作主成分点到原点的距离(DA)、AMMI稳定性值(ASV)和基于GGE双标图分析的试点到原点的距离(DG)对西南玉米区域试验试点的区辨力进行评价,进而用秩次相关分析和主成分分析揭示试点区辨力评价方法间的内在关系。结果表明,两年试验品种间、试点间均存在极显著差异,且品种和试点间互作也极显著;8个统计数也许可以用来度量试点的区辨力,但是不同统计数对同一年度内试点的区辨力评价结果不完全一致;统计数CV、GCV、WE、DA和DG间都存在极显著的秩次相关,但是统计数DG也许更有利于评价试点的区辨力。     

A method of analyzing cultivar x location x year experiments: a new stability parameter

Summary Assessment of cultivar performance in a cultivar x location x year experiment is often difficult because of the presence of a location x year interaction. Our objective is to demonstrate a method on separation of environment effects (location x year) into predictable and unpredictabel components. The analysis consists of two parts: (1) a regression analysis based on location effects (averaged over years), assuming that the location means represent predictable environmental variation; and (2) the estimation of stability (denoted type 4) based on the years within location mean squares, assuming that years within location represent unpredictable environmental variation. From the regression analysis in (1), a breeder can determine the optimum range of locations in which a cultivar is well suited, and from (2) he can choose the most stable cultivars. The advantage of type 4 stability is that it is independent of the other cultivars included in the test and of the regression coefficient estimated for predictable variation. Three sets of published data are used to illustrate the analysis. Type 4 stability is compared with type 3 stability (deviation mean square from regression on environmental index) for genetic consistency. The analyses suggest that type 4 stability is consistent and is therefore a potential genetic parameter, but type 3 stability is not.Contribution No. I-806 from Engineering and Statistical Research Centre, Research Branch, Agriculture Canada, Ottawa, K1A OC6, Canada     

Efficiency of potato breeding using FDR 2n gametes for multitrait selection and progeny testing

Summary The objective of this research was to compare the efficiency of the 4x×2x breeding scheme with the traditional 4x×4x method with respect to potato improvement. The basis for such a comparison was the parental value of four 2x and four 4x male parents from the International Potato Center (CIP) as measured by multitrait selection and progeny testing. The 2x parents produced 2n pollen by parallel spindles at anaphase II, which is genetically equivalent to a first division restitution (FDR) mechanism. Both 2x and 4x parents were crossed with four common 4x female parents. Thus, 32 families were evaluated over 2 years at four Peruvian locations. A selection index which considered tuber yield, tuber number, average tuber weight and specific gravity was used for multitrait selection. Three FDR 2x parents had better selection index scores than the 4x parents over the four locations. Estimates of broad-sense heritability for total yield using different number of replications and locations were calculated by using the variance components. The 4x × 2x breeding scheme was found to be better than the traditional 4x × 4x method since fewer replications and locations are required to evaluate tuber yield in 4x × 2x progenies than in 4x × 4x progenies. The FDR 2x parents were also better material than the 4x parents for testing combining ability for tuber yield of the 4x progenitors. This could be the result of the mode of FDR 2n pollen formation. The pollen of FDR 2x parents is more heterozygous, but more homogenous than n pollen from 4x parents.Paper from the Laboratory of Genetics. Research supported by the College of Agricultural and Life Sciences; International Potato Center; USDA-CRGO-88-37234 3619, and Frito-Lay, Inc., USA     

Estimation of heritability from varietal trials data

We present the estimation of heritabilities of an observed trait in situations where evaluation of several pure breeding lines is performed in a trial at a single location and in trials from several locations. For the single location situation, we evaluate exact confidence intervals, the probability of invalid estimates, and the percentage points of the distribution of heritability. Simulations were performed to numerically verify the results. Additionally, approximations to the bias and standard error of the estimate were obtained and are presented along with their simulated values and coefficients of skewness and kurtosis. For trials in several locations, explicit expressions for exact values of confidence limits are not available. Further, one would require knowledge of one more parameter, represented by the ratio of genotype x environment (G x E) interaction variance to error variance, in addition to the number of genotypes, replication and true heritability value. Approximations were made for bias and the standard error of estimates of heritability. The evaluation of the distribution of heritability and its moments was recognized as a problem of the linear function of an independent chi-square. The methods have been illustrated by data from experiments on grain and straw yield of 64 barley genotypes evaluated at three locations.     

Climatic impact,future biomass production,and local adaptation of four switchgrass cultivars

Previous studies have shown that switchgrass has a wide range of genetic variation and that productivity is linked to local adaptation to the location of origin for many cultivars. In this meta‐analysis, we compiled and analyzed 900 observations associated with 41 field trials for four switchgrass cultivars (two lowlands, Alamo and Kanlow, and two uplands, Cave‐In‐Rock and Shelter). This extensive dataset and machine learning were used to identify the most influential variables impacting switchgrass productivity, to search for evidence of local adaptation to each cultivar's location of origin, and to predict change in productivity under future climate for each cultivar. In general, variables associated with climate and management are more important predictors of productivity relative to soil variables. Three climatic variables, annual mean temperature, annual precipitation, and precipitation in the wettest month, are identified as key environmental variables for productivity of all cultivars. Productivity under future climate (2041–2060) is predicted to stay stable for all cultivars relative to the prediction under current climate (1986–2005) across all trial locations and over a 20‐year simulation period. However, the productivity of each cultivar varies from location to location and from year to year, although productivity varies more between locations than between years. Additionally, we observe shifts in the most productive cultivar at the local field scale depending on the combination of management practice and climates. The shape of the relationship between productivity and the annual mean temperature relative to the cultivar's location of origin is a bell‐shaped curve for Kanlow, Cave‐in‐Rock, and Shelter, indicative of local adaptation. Identifying influential environmental variables and their relationships to productivity with respect to cultivar's location of origin help predicting productivity on the local field scale, and will help with the biofuel production planning through the selection of suitable cultivars for different locations under climate changes.     

Stability analysis of grain yield in barley (Hordeum vulgare) in the US mid-Atlantic Region

Stability of grain yield performance is an important characteristic in the selection of new crop cultivars. Information from cultivar trials, however, is seldom fully analysed for genotype by environment interactions and, therefore, information on stability of current crop cultivars is lacking. The objectives of this study were to investigate the stability of agronomic traits among genotypes of barley (Hordeum vulgare) across 17 environments (location‐years) in Maryland (USA) from 1994 through 1997 and to examine the effect of locations and years of testing on grain yield performance in this region. Significant differences were observed among barley cultivars and experimental lines for grain yield, plant height, and heading date. Grain yield was positively correlated with plant height and negatively correlated with heading date. Genotype x environment interactions measured through regression analysis were significant for grain yield, heading date and plant height, with the environmental component having the largest effect. Most barley genotypes tested (90%) had regression slopes for grain yield that did not differ from 1.0, indicating good potential for yield response under improving environmental conditions. The most widely grown cultivar in the mid‐Atlantic region, ‘Nomini’, had a regression slope that was higher than 1.0 for grain yield. This indicates that it tends to respond with increasingly higher yields under favorable conditions. In this study, the slope and the standard error of the slope were moderately correlated with grain yield. The genotype's coefficient of variation was not a good indicator of stability for this region. Grain yields of genotype entries common to all years and locations were correlated with corresponding yields at each of the locations and years to assess the relative performance of each location and year. Correlation coefficients across locations were relatively high (r=0.64) within each year of testing. Correlations between years for the same and across locations were generally much lower. The data presented here supports a testing program over more years rather than increased locations to fully characterise the performance of new cultivars.     

A comparative evaluation of two methods of selecting locations used for testing spring wheat cultivars

Summary One of the considerations of regional cultivar evaluation programs is to optimize the number of locations used for testing. Although optimization of numbers of locations using cluster analysis has been previously attempted, no objective comparison of methods has yet been made. A new clustering method that uses the pairwise contribution of locations to the cultivar x location mean square as the distance measure (LB) was compared to another method that employs diallel correlations as the distance measure (CL). Data from six spring wheat (Triticum aestivum L. em Thell) cultivars grown at 13 locations for five years were used in the initial cluster analysis. Another set of data, from a separate year, consisting of yields of the original 6 cultivars and a set of 12 independent cultivars was then used to check the validity of the original groupings and to compare the two methods. When the 6 original cultivars were considered, the LB technique was found to be superior to the CL. When the 12 independent cultivars were used, neither method was considered to be superior. Because of the lack of flexibility on the part of the LB method, neither technique could be deemed as fully adequate.Contribution Number 842 of the Department of Plant Science, University of Manitoba, Winnipeg, Manitoba, Canada     

Genetic properties of four types of stability parameter

Summary The genetic properties of four types of stability parameter for individual genotypes were investigated using a set of diallel cross data (28 genotypes x four locations x 3 years). The specific parameters studied were: the variance of a genotype across environments (T1); the genotype x environment (GE) interaction effect for a genotype, squared and summed across all environments (T2); the residual mean square (MS) of deviations from the regression of a genotype on an environmental index (T3); and years within locations MS for a genotype, averaged over all locations (T4). Each stability statistic was fitted to the additive model, based on the assumption that if the stability parameter is heritable, stability of F₁ is most likely to be the average stability of its parents. The results showed that T1 and T4 were additive, but T2 and T3 were not. A study of the consistency of stability rankings between two seeding rates over the same set of environments showed a similar pattern. It appears that stability parameters of types 1 and 4 are heritable, and thus useful for selection, while those of types 2 and 3 are nonheritable, and thus not useful.Contribution No. R-029     

Classification of cowpea cultivars for field resistance to the legume pod borer, Muruca testulalis in Nigeria using cluster analysis

Cluster analysis was used to classify cowpea cultivars developed for resistance to M. testulalis in Nigeria based on data collected on four damage parameters. The cultivars were grouped into classes for each of two locations under two protection regimes. Differences were observed in the groupings for the two locations while one cultivar, MR×6–84F was found to have wide adaptability in the presence or absence of M. testulalis infestation. This is particularly useful for the selection of breeding materials in cultivar improvement for specific or general ecological zones.     

Variation in seedling susceptibility to Bremia lactucae (lettuce downy mildew) in the absence of effective major resistance genes

In the absence of effective major genes the importance of interactions between cultivar genotype, isolate genotype and environment was investigated in experiments using seedlings of eight lettuce cultivars inoculated with three isolates of Bremia lactucae and grown under a number of different environmental conditions. The outcome of the cultivar-isolate association was measured using four criteria and the data were examined by analysis of variance and correlation. The relative susceptibility of cultivars was generally independent of environment and there was no evidence that isolates were adapted to particular cultivars. Although significant cultivar X isolate interactions were found in individual experiments they were not consistent between experiments, even where these were conducted under apparently identical conditions. Variation resulted from either cultivar X environment or isolate X environment interaction with the environment always the dominant variable.     

Mapping QTL main and interaction influences on milling quality in elite US rice germplasm

Rice (Oryza sativa L.) head-rice yield (HR) is a key export and domestic quality trait whose genetic control is poorly understood. With the goal of identifying genomic regions influencing HR, quantitative-trait-locus (QTL) mapping was carried out for quality-related traits in recombinant inbred lines (RILs) derived from crosses of common parent Cypress, a high-HR US japonica cultivar, with RT0034, a low-HR indica line (129 RILs) and LaGrue, a low-HR japonica cultivar (298 RILs), grown in two US locations in 2005–2007. Early heading increased HR in the Louisiana (LA) but not the Arkansas (AR) location. Fitting QTL-mapping models to separate QTL main and QTL × environment interaction (QEI) effects and identify epistatic interactions revealed six main-effect HR QTLs in the two crosses, at four of which Cypress contributed the increasing allele. Multi-QTL models accounted for 0.36 of genetic and 0.21 of genetic × environment interaction of HR in MY1, and corresponding proportions of 0.25 and 0.37 in MY2. The greater HR advantage of Cypress in LA than in AR corresponded to a genomewide pattern of opposition of HR-increasing QTL effects by AR-specific effects, suggesting a selection strategy for improving this cultivar for AR. Treating year–location combinations as independent environments resulted in underestimation of QEI effects, evidently owing to lower variation among years within location than between location. Identification of robust HR QTLs in elite long-grain germplasm is suggested to require more detailed attention to the interaction of plant and grain development parameters with environmental conditions than has been given to date.     

Age–age and trait–trait correlations for <Emphasis Type="Italic">Eucalyptus grandis</Emphasis> Hill ex Maiden and their implications for optimal selection age and design of clonal trials

Previous results from seven locations of Eucalyptus grandis clonal trials in Colombia supported the a priori contention of sub-dividing them into three different environmental zones for testing and deployment. Within these zones, the determination of age-age genetic correlations for both height and mean annual increment (MAI) showed that strong age-age correlations are present for a rotation age of 6 years starting at 3 years age and, thereafter, suggesting this age as appropriate for selection. This biological selection age coincides with an "economical" age for selection based on discounted selection efficiency in perpetuity, considering a range of interest rates between 10% and 20%. High genetic correlations between wood density at 3 years and 6 years as well as the lack of genetic correlation between this trait and growth traits, also favors selection at age 3 and facilitates breeding strategies that consider the utilization of both traits for improvement. A simulation of optimal clonal test designs indicated that by using six locations and six blocks per location in a single-tree plot design, between 80% and 90% of the maximum selection efficiency could be obtained. This type of design allows testing of a large number of genotypes across a reasonable number of locations in a cost-effective manner.     

Comparison of unpredictable environmental variation generated by year and by seeding-time factors for measuring type 4 stability

Summary Type 4 stability has been proposed to measure a cultivar's homeostatic property to resist unpredictable environmental variation. The requirement for calculating this stability is that the experiment must contain a time factor in addition to the cultivar x location factors. Of the two time factors, year and seeding-time, the latter is less attractive biologically because it represents only a part of the broader context of unpredictable variation represented by years, but it is attractive in terms of shortening the test period. Investigation of historical data from the Eastern Cooperative trials and the Ontario Production trials in Canada indicates that the unpredictable variation generated by seeding-time was about half that generated by year. Although type 4 stability measured by both factors appears to be the same, the stability measured by seeding-time is more prone to variation. The implication is that complete substitution of the year factor by seeding-time is not appropriate, but use of both factors in combination may be sensible.Contribution No. C-055 from the Engineering and Statistical Research Centre, Research Branch, Agriculture Canada, Ottawa, K1A 0C6, Canada     

Genetic analysis of resistance to Puccinia striiformis f.sp. tritici in cv. Aflak at adult plant stage

In order to investigate heritability and gene action for yellow rust resistance in wheat, a resistance yellow rust cultivar Aflak was crossed to susceptible cultivar Avocet‘s’. Parents, F₁, F₂ and F₃ generations were cultured according to randomised complete block design with two replications in the research station of Gharakhil, Iran. Parents and other generations were inoculated with 70E0A+ race. Traits including severity and infection type were recorded and then coefficient of infection was calculated. For this trait, generations mean and variance analysis were performed and results showed that there were significant differences among generations for coefficient of infection. Results showed that in addition to additive and dominance effects, at least one kind of epistasis interaction (additive × additive) control this trait. Although additive and dominance effects control this trait, but with attention to generations variance analysis, the results showed that additive variance had important role to control this trait.     

Analysis of Variety Trials in the Presence of Non-Random Time Effect

The assumption of random year effect in the analysis of variety trials data over locations and years clearly contradicts the practice of conducting the trials over only a few consecutive years. A method of analysis of such trials which assumes that the year-dependent effects are serially correlated is proposed in this paper to cater for the non-randomness in the selection of years of the experiments. A simple autoregressive model was assumed for the serial relationship. A reduction in the variance estimate of the difference between two variety means was obtained using this method.     

Fusarium oxysporum and post-emergence herbicide for the control of the parasitic plant Striga hermonthica in maize

Two trials were conducted to evaluate the efficacy of a granular mycoherbicide formulation based on Fusarium oxysporum and post-emergence herbicide for the control of the parasitic plant, Striga hermonthica in the Nigerian Savanna. Four fungal treatments were used: F. oxysporum followed by 2,4-D, F. oxysporum followed by supplementary hoe weeding, F. oxysporum followed by Triclopyr and a control (No F. oxysporum but hoe-weeded). The experiments were laid out in a split plot design with three replications in the two locations. The two varieties (Across 97 TZL and farmer's local variety) formed the main plot treatments, while the Striga fungal treatments formed the sub-plot treatments. At the Lafia location, the emergence of Striga was delayed by 7 days (46 days) as compared to the Makurdi location, which germinated earlier 39 days after sowing. Maize variety Across 97 TZL similarly delayed the time to Striga emergence when compared to the farmer's local variety. However, the different Striga control methods did not have any significant effect on the time of Striga emergence. Generally, number of maize plants infected with Striga was highest with the farmer's local variety throughout the period of observation, while in the Striga control treatments, hoe-weeded check recorded the highest; the minimum was obtained with plots treated with F. oxysporum followed by postemergence application of Triclopyr at the rate of 0.36 kg a.i./ha at 6 weeks after sowing. Highest maize grain yields were obtained at Lafia with Across 97 TZL and plots treated with F. oxysporum followed by either post-emergence 2,4-D or Triclopyr at 0.36 kg a.i./ha each. The results demonstrate the high potentiality of using F. oxysporum as a spot application at planting followed by post-emergence herbicide (2,4-D or Triclopyr) application at 6 weeks after sowing for the control of the parasitic plant S. hermonthica in the Nigerian Savanna.     

Biomass yield in a genetically diverse Miscanthus sacchariflorus germplasm panel phenotyped at five locations in Asia,North America,and Europe

Miscanthus is a high-yielding bioenergy crop that is broadly adapted to temperate and tropical environments. Commercial cultivation of Miscanthus is predominantly limited to a single sterile triploid clone of Miscanthus × giganteus, a hybrid between Miscanthus sacchariflorus and M. sinensis. To expand the genetic base of M. × giganteus, the substantial diversity within its progenitor species should be used for cultivar improvement and diversification. Here, we phenotyped a diversity panel of 605 M. sacchariflorus from six previously described genetic groups and 27 M. × giganteus genotypes for dry biomass yield and 16 yield-component traits, in field trials grown over 3 years at one subtropical location (Zhuji, China) and four temperate locations (Foulum, Denmark; Sapporo, Japan; Urbana, Illinois; and Chuncheon, South Korea). There was considerable diversity in yield and yield-component traits among and within genetic groups of M. sacchariflorus, and across the five locations. Biomass yield of M. sacchariflorus ranged from 0.003 to 34.0 Mg ha⁻¹ in year 3. Variation among the genetic groups was typically greater than within, so selection of genetic group should be an important first step for breeding with M. sacchariflorus. The Yangtze 2x genetic group (=ssp. lutarioriparius) of M. sacchariflorus had the tallest and thickest culms at all locations tested. Notably, the Yangtze 2x genetic group's exceptional culm length and yield potential were driven primarily by a large number of nodes (>29 nodes culm⁻¹ average over all locations), which was consistent with the especially late flowering of this group. The S Japan 4x, the N China/Korea/Russia 4x, and the N China 2x genetic groups were also promising genetic resources for biomass yield, culm length, and culm thickness, especially for temperate environments. Culm length was the best indicator of yield potential in M. sacchariflorus. These results will inform breeders' selection of M. sacchariflorus genotypes for population improvement and adaptation to target production environments.     

Plot size for progeny selection in maize (Zea mays L.)

Summary Six progeny trials that included 147 half-sib progenies of maize (Zea mays L.) population ESALQ PB-5 were conducted for the purpose of studying plot size and its consequences in recurrent selection programs. The progenies were evaluated in three 7x7 duplicate simple lattice experiments using one-row plots of 5 m². At harvest each plot was partitioned into five sub-plots (sampling units), and data was collected from each sampling unit. At the same time and place the same progenies were evaluated in three 7x7 duplicate simple lattice experiments using 1-m² (linear row with 5 plants) plots. Data were collected for plant and ear height, ear diameter, total ear weight, and total grain yield. The data were combined by using adjacent sampling units, and the analyses were performed by considered five plot sizes in addition to those of the independent trials with 1-m² plots. The experiments with 1-m² plots were less efficient in discriminating for yield traits among progenies than those with 5-m² plots. The combination of plot size and number of progenies evaluated indicated that an optimum plot size for yield was between 3 and 4 m², or 15–20 plants per plot. With such sizes the expected gain was maximized for the four replications used in this study. If the total area covered by each progeny is constant, the maximum gain from selection, however, is attained by decreasing plot size and increasing the number of replications. The minimum size of plots is, however, limited by practical or theoretical criteria. Plot size affected the estimates of additive genetic variance, coefficient of heritability, and genetic coefficient of variation for all of the traits. No practical limitation was observed for conducting experiments with 1-m² plot.     

我国旱地春小麦产量及主要农艺指标的变异分析

采用4年、13个品种(系)、18个试点组成的全国旱地春小麦区域试验产量资料,通过联合方差分析和基因型及其与环境互作（GGE）双标图分析,研究了基因型、环境、基因型与环境互作效应（GEI）对产量变异的影响及品种的产量稳定性.结果表明：环境对产量变异的影响远大于基因型和GEI,环境引起的产量变异占87.5%～92.0%．互作因素中以地点×基因型的互作效应最大,基因型×年份的互作效应最小.我国旱地春小麦基因型多年多点的平均产量水平为2550 kg·hm^-2.产量三要素中,千粒重受环境的影响最小.影响产量变异的主要环境因子有：≥10 ℃年积温、生育期降雨量、平均气温、海拔、年降雨量和无霜期.产量与单位面积穗数（0.675^**）、穗粒数（0.581^**）、千粒重（0.456^**）呈极显著正相关,产量三要素间也呈正相关（0.244～0.480^**）,处于可同步提高范围.