Predicting the relative effectiveness of direct versus indirect selection for oat yield in three types of stress environments

Summary In breeding crop varieties for stress environments, it must be decided whether to select directly, in the presence of stress, or indirectly, in a nonstress environment. The relative effectiveness of these two strategies depends upon the genetic correlation (r _g ) between yield in stress and nonstress environments and upon heritability in each. These parameters were estimated for grain yield of 116 random oat lines grown in nonstress, P-deficient, N-deficient, and late-planted environments. Estimates of r _g between yield in nonstress and yield in P-deficient, N-deficient, and late-planted environments were 0.52±0.24, 1.08±0.16, and 0.06±0.24, respectively. No consistent relationship between heritability and environment mean yield was observed. Direct selection in the presence of stress was predicted to be superior for yield in low-P and late-planted environments, but indirect selection in high-N environments was predicted to be as effective as direct selection in producing yield gain in low-N environments. These results confirm that neither high-yield environments nor environments in which the heritability of yield is maximized are necessarily optimum when the goal is to maximize yield gain in stress environments.Dep. of Agronomy, Iowa State Univ., Ames, IA 50011; USA, Journal Paper no. 13101. Project 2447.     

Conditions under which selection for mean productivity, tolerance to environmental stress, or stability should be used to improve yield across a range of contrasting environments

Computer simulations were conducted to determine whether conclusions obtained for the special case of a single stress and a single non-stress environment apply to the more general situation where a population of testing environments includes a range of stress and non-stress environments. Mean productivity, tolerance to environmental stress, and a regression coefficient stability parameter of genotypes across environments were compared to determine conditions under which these selection criteria should be used to improve yield across a range of contrasting environments. The results obtained from a worked example based on the single crosses from a 7 × 7 diallel cross in maize and the simulation experiment showed that the conclusions of Rosielle & Hamblin (1981) cannot be directly applied to a population of stress and non-stress environments. Selection for mean productivity should increase yield in both stress and non-stress environments unless the genetic variance in stress environments is more than double that in non-stress environments, and the genetic correlation between yields in contrasting environments is highly negative. Mean productivity and tolerance were shown to be positively correlated even if the genetic variance in stress environments is half that in non-stress environments. Genotypes with a high tolerance to stress were found to have low regression coefficient stability parameters, even when a range of stress and non-stress environments was used. This revised version was published online in July 2006 with corrections to the Cover Date.     

Contributions to the Analysis of Genotype × Environment Interactions: Theoretical Results of the Application and Comparison of Clustering Techniques for the Stratification of Field Test Sites

For an analysis of cross-classified data sets with rows = genotypes and columns = environments (locations and/or years), existing genotype × environment interactions are of major importance. Differential responses of genotypes (environments) across environments (genotypes) are expressed by these effects. To reduce the impact of these genotype × environment interaction effects, one commonly stratifies genotypes or environments by cluster analysis techniques into homogeneous groups so that interactions within groups are minimized. The present paper presents a comprehensive overview of the numerous procedures for stratification of genotypes or environments by cluster analysis which have been proposed in the literature. In these studies, two different concepts of interaction have been used: the crossover concept of interaction [different rank orders of genotypes (environments) within environments (genotypes)] or the usual statistical concept of interaction (deviations from additivity of main effects in the linear model). For a quantitative characterization of cluster techniques and for a comparison of two different clustering procedures, two parameters are introduced and discussed: measure of resemblance for two classifications and cluster size for one classification.     

Grain-yield characteristics of oat lines surviving uniform and shuttle selection strategies

Summary Four selection strategies were used on four sets of oat lines to select for grain yield. Two of these used uniform environments whereby sequential selection of the high-yielding lines occurred in continuous high- or continuous low-productivity environments. These are referred to as high and low uniform selection strategies, respectively. The other two selection strategies were conducted by sequential selection of the high-yielding lines in alternating high- and low-productivity environments. They are referred to as high and low shuttle selection strategies, respectively, with high and low designating the productivity of the first environment in the sequence. After three or four cycles of selection, the surviving lines and a random sample from each set were evaluated for mean grain yield, grain yield response to improving environments, and stability of grain yield, in a range of environments typical of oat production on Iowa farms.Grain yield and regression response for all selection strategies, when calculated across all sets of lines, were significantly greater than corresponding values for random samples. Stability was unchanged. The uniform-high and uniform-low strategies gave the greatest and the smallest gains in mean grain yield, respectively, with the shuttle strategies giving intermediate gains. Shuttle selection in predominantly high-productivity environments increased grain yield more than shuttle selection in predominantly low-productivity environments. The uniform-strategy followed by the shuttle-high strategy identified entries with superior performance in high productivity environments. Increased gain in mean grain yield across all environments was associated with increased number of selection cycles conducted in high-productivity environments.Journal Paper No. J-15252 of the Iowa Agric. and Home Econ. Exp. Stn., Ames, Iowa 50011, USA. Project No. 2447.     

Influence of environmental productivity levels and yield stability on selection strategies in soybean

Summary Yield data were collected for soybean (Glycine max (L.) Merr.) lines in maturity groups III and IV in 14 environments from 1985 to 1989. The lines in each maturity group were subdivided into three different groups based on the mean yield over all environments, and the genotype × environment interactions were studied for each group. Yield stability of the lines was determined. Effectiveness of selection based on different types of environments was examined.Productivity level of the environment did not influence the relative ranking of the lines. Significant rank correlations occurred between mean yields in most environments and the overall mean yield, but few similarities occurred in the line rankings among individual environments. High-yielding lines contributed a significantly smaller proportion to the genotype × environment interaction than medium- and low-yielding lines.A small proportion of the lines were below or above average stability. Significant correlations occurred among stability, overall mean yield, and mean yield in high- and low-yielding environments. However, few significant correlations occurred between individual environment yields and stability in high- or low-yielding environments. Maturity groups differed in yield and stability relationships. Stability in high- and low-yielding environments did not adequately predict stability for each other.Contribution No. 93-445-J from the Kansas Agricultural Experient Station     

Pattern analysis on grain yield performance of Chinese and CIMMYT spring wheat cultivars sown in China and CIMMYT

Understanding the relationships among testing environments is essential for better targeting cultivars to production environments. To identify patterns of cultivar, environment, cultivar-by-environment interactions, and opportunities for indirect selection for grain yield, a set of 25 spring wheat cultivars from China and the International Maize and Wheat Improvement Center (CIMMYT) was evaluated in nine environments in China and four management environments at CIMMYT in Cd. Obregon, Mexico, during two wheat seasons. Genetic background and original environment were the main factors influencing grain yield performance of the cultivars. Baviacora M 92, Xinchun 2 and Xinchun 6 showed relatively more stable and higher grain yields, whereas highly photoperiod sensitive cultivars Xinkehan 9, Kefeng 6 and Longmai 19 proved consistently inferior across environments, except in Harbin and Keshan, the two high latitude environments. Longmai 26, also from high latitude environments in the north-eastern Heilongjiang province, was however probably not as photoperiodicly sensitive as other cultivars from that region, and produced much higher grain yield and expressed a broader adaptation. None of the environments reported major diseases. Pattern analyses revealed that photoperiod response and planting option on beds were the two main factors underlying the observed interactions for grain yield. The production environment of planting on the flat in Mexico grouped together with Huhhot and Urumqi in both wheat seasons, indicating an indirect response to selection for grain yield in this CIMMYT managed environment could benefit the two Chinese environments. Both the environment of planting on the flat with Chinese Hejin and Yongning, and the three CIMMYT environments planting on raised beds with Chinese Yongning grouped together only in one season, showing that repeatability may not be stable in this case.     

Evaluation of environments for preliminary testing of maize for yield and stover digestibility

Summary The identification of environments suitable for selection should enable plant breeders to test reliably a larger number of genotypes with given resources. This research was undertaken to evaluate discrimination ability (DA) and prediction ability (PA) of eight environments involving two locations. Eckartsweier (Eck) 1 and Voelkenrode (Voe); 2 yer. 1984 (84) and 1985 (85); and two harvests, silage harvest (I) and later (II). It was based on dry matter yield of plant (PDMY), ear (EDMY) and stover (SDMY) and on in vitro digestible organic matter (IVDOM), neutral detergent fibre (NDF), acid detergent fibre (ADF) and acid detergent lignin (ADL) of stover of 12 inbred lines and their 66 diallel crosses in maize (Zea mays L.). Linear regression coefficient of the performance of genotypes in an environment on that averaged across all environments and its degree of determination were used as measures of the DA and PA of environments, respectively. In hybrids, the DA of environments differed significantly for all traits except SDMY and ADL. Environment Eck851 showed better PA (0.63) than other environments for PDMY, EDMY, IVDOM, NDF, and ADF. Among the 12 two-environment combinations. EckI was a better predictor for PDMY, EDMY, IVDOM and NDF (PA0.80). The more productive environments showed better DA and PA for PDMY and FDMY than less productive ones. For IVDOM and NDF the first harvest provided better discrimination and prediction than the second harvest. In inbred lines the DA of environments differed significantly for EDMY only. In the present study, PA and DA seemed to be functions of the environments, PA was improved by combining two environments, and some environments seemed to be suitable for preliminary selection of genotypes for such diverse traits as yield and digestibility.     

棉花纤维品质性状的遗传稳定性研究

通过 4个环境条件下纤维品质的表现及 5个陆地棉品系的完全双列杂交分析 ,对陆地棉纤维品质性状的遗传稳定性进行了研究。结果表明纤维比强度、绒长、麦克隆值及伸长率广义遗传率高 ,受环境影响相对较小 ,不同环境、品种间差异较一致 ;比强度、绒长与环境的互作小 ;而麦克隆值和伸长率与环境的互作较大 ;纤维整齐度广义遗传率小 ,受环境影响大。由于不同年份各纤维性状数值变化 ,结果难以比较 ,建议用陆地棉遗传标准系 TM- 1作为共同对照 ,用与共同对照的比值进行分析 ,并应加强纤维品质性状的分子标记辅助育种研究     

Classification of Global Environments and Cultivars of Spring Barley Based on Heading Time Interactions

Global heading time data collected by the International Center for Maize and Wheat Improvement (CIMMYT) during the International Barley Yield Trials were used to assess similarity of environments, variation among cultivars, and genotype × environment interactions. Data for 29 spring barley cultivars grown in 89 environments over three years were analyzed by cluster analysis. The deviation m days to heading of the mean of 28 photoperiod sensitive cultivars from the cultivar ‘Mona’ and the mean of ‘Mona’, homozygous recessive for the ea_k gene conferring photoperiod insensitivity and thermal stability, were used as environmental coordinates. In addition, diversity of heading time responses among genotypes was illustrated by differences among overall means and patterns of deviation for days to heading from ‘Mona’ in selected environments. Three main clusters were identified. Mexican environments were similar to warmer Mediterranean, eastern and southern African, West Asian, and Latin American environments. Heading time responses in Syria were similar to those observed m other cool Mediterranean environments. Early heading cultivars exhibited greater variation for heading response, especially in extremely warm-and equaiorial- short daylength environments, com-pared to late heading cultivars, presumably because of larger photothermal × genotype interactions. Photoperiod flux about the winter solstice appeared to be a major environmental cue for heading time in photoperiod sensitive spring barleys.     

Specific and General Adaptation and Yield Stability of Wheat (Triticum aestivum L.) Genotypes

Mean grain yield performance of 12 wheat and one triticale genotypes were measured at four locations over four consecutive years, using a randomized complete block design with four replications. The genotypes used were commercial cultivars and advanced lines from different wheat breeding projects located in different areas in Iran. Two locations were in semiarid regions and the other two locations in the temperate zones. The combined analysis of variance indicated highly significant genotype-environment (GE) interactions. From combinations of locations and years three sets of environments were generated. Set I and set II, each, consisted of eight environments (two locations and four years) representing semiarid and temperature environments, respectively. Set III consisted of 16 environments including both semiarid and temperate conditions. Set I and set II were used to measure specific adaptation of the genotypes while set III was employed for measuring general adaptation. The methods of Eberhart and Russell (1966) were used for partitioning GE interactions. The mean square associated with the heterogeneity of regression was highly significant under all sets of environments. These observations indicated that a major part of GE interaction could be accounted for by differences in the regression of the individual genotypes. All the genotypes had significant regression mean square under set I, set II, and set III environments, with the exception of two genotypes under set II. However, mean yields, regression coefficients, and the mean squares associated with deviation from regression greatly varied over the sets of environments. Only three genotypes, a commercial cultivar and two new advanced line, were identified as having specific adaptation and yield stability to semiarid environments. Among all the genotypes, only a commercial cultivar was identified as adapted and stable to temperate conditions. Two of the three genotypes which were adapted to semiarid environments also showed general adaptation to set III environments. However, the mean yield of these two genotypes under semiarid conditions (set I) were significantly greater than their respective mean yields under set III environments. Thus, wider adaptability was compensated by lower mean yield. The present study indicates that, while a wide range of environments is necessary and recommended for measuring general adaptation reactions and yield stability of various genotypes, one should not ignore the possibility of finding some genotypes with specific adaptation to specific environments and thus maximizing yield production. Stable genotypes with general of specific adaptation should be utilized in breeding projects in order to develop even more desirable lines.     

Comparison of intra- and inter-pool crosses in faba beans (Vicia faba L.). I. Hybrid performance and heterosis in Mediterranean and German environments

Two recently detected, promising CMS systems in faba bean have opened up new possibilities in hybrid breeding. This study was conducted to determine hybrid performance and heterosis of 33 intra-pool and 66 inter-pool crosses from a factorial of six European small-seeded (Minor), six European large-seeded (Major), and eight Mediterranean faba bean lines. The parent lines and F₁ crosses were evaluated at two German and seven Mediterranean environments for anthesis, maturity, yield, yield components and plant height. Yield in the Mediterranean environments was 60% of that in the German environments. European Minor lines and their intra-pool crosses were unadapted to Mediterranean environments and yielded only 31 % compared with the Mediterranean lines and their crosses, whereas European Major genotypes yielded 58%. In German environments the European crosses yielded 107% of the Mediterranean crosses. Heterotic yield increase over the parental mean was largest for European Minor x Mediterranean inter-pool crosses, amounting to 95% in the Mediterranean and 73% in German environments. Our results confirmed the expectation of an increased heterosis in inter-pool over intra-pool hybrids and poor adaptation of European genotypes in Mediterranean environments. In the latter, Mediterranean intra-pool hybrids were the most promising, whereas in Germany inter-pool hybrids of the European Minor × Mediterranean type were most promising.     

栽培环境对番茄部分数量性状DUS测试结果的影响

为了探索不同栽培环境对番茄部分数量性状DUS测试结果的影响,选取对30个番茄DUS测试标准品种和2个测试品种及其选定的2个近似品种,进行塑料大棚和露地2种不同的栽培环境对番茄10个数量性状的DUS测试结果影响的研究。结果表明：2种栽培环境对除第一花序着生节位和心室数以外的8个数量性状均存在显著或极显著的影响,导致在部分数量性状代码判别和特异性的判定上存在着差异。通过标准品种数量性状分级标准的校正,可以有效消除因栽培环境不同而造成的影响。     

Response of Sericea Lespedeza Genotypes Low in Tannins to Different Environments

Transfer of the low-tannin trait to otherwise desirable sericea lespedeza high-tannin lines produced genotypes with considerably lowered forage yield. It is not known if low-tannin sericeas are proportionally less productive than high-tannin sericeas in high-yielding environments. If so, low-tannin sericeas would be less desirable to grow in more productive environments. Regression analysis was used to partition GE interactions between regressions and the residuals after regression, and to measure the response to changing environments, Shukla 's stability-variance parameters were used to measure genotype stability. Variance and coefficient of variation were calculated across environments for each genotype and rank correlated to the aforementioned parameters of stability to determine their usefulness in the early stages of cultivar testing. Stability analysis was carried out on the dry forage yield of 10 genotypes grown in 10 environments in Alabama. The only low-tannin genotype that consistently responded to environmental fluctuations like ‘Serala’ was 74-100-5. Low-tannin sericeas were found to be proportionally less productive than high-tannin sericeas in high-yielding environments. However, it is possible to select low-tannin lines with an environmental response similar to high-tannin sericeas. Rank correlations among stability parameters indicated that EV is a stability parameter which is easy to calculate and could be used in the early stages of cultivar testing.     

利用永久F2群体在不同光周期环境下定位玉米株高QTL

为了研究热带玉米株高的遗传机制, 利用温热组合黄早四×CML288衍生的重组自交系群体构建了一个包含278个组合的永久F₂群体, 分别在海南三亚、河南郑州和洛阳、北京昌平和顺义等5个地点3种光周期环境中进行株高鉴定。利用复合区间作图法在3种光周期环境下共定位到12个不同的玉米株高QTL。位于第1染色体上的qPH1-2和位于第4染色体上的QTL qPH4在3个环境中同时被检测到, 表明这2个QTL在不同日照环境下均能稳定表达。位于第3染色体上的qPH3在短日照环境下能解释株高遗传变异的32.13%, 而在2个长日照环境下并未被检测到, 表明此QTL是短日照环境下特异表达的主效QTL。第10染色体上QTL qPH10-1分别解释2个长日照环境中株高遗传变异的25.39%和39.58%, 是长日照环境下特异表达的主效株高QTL。     

基于单片段代换系的玉米百粒重QTL分析

籽粒大小是影响玉米产量的关键因素。本研究基于59份玉米染色体单片段代换系(SSSL)纯合体,对玉米百粒重性状进行2年6个试验环境的表型鉴定,利用t测验和重叠群作图的方法对SSSL内代换片段上的百粒重效应进行了QTL分析。共检测出20个百粒重QTL,分布在玉米的8条染色体上,其中14个(70.0%)在2个以上试验环境中被重复检出,4个(20.0%)在4个以上试验环境中被重复检出,在全部6个试验环境中重复检出且基因加性效应值较大的玉米百粒重QTL是位于玉米第5染色体Bin5.05区SSR分子标记bnlg278和umc1680附近的q100kw-5-3。研究结果为玉米籽粒大小性状相关基因的进一步精细定位和克隆奠定了基础。     

Analysis of genotype-by-environment interaction for grain yield of rainfed durum wheat genotypes in warm winter areas of Iran

This study was performed for pattern analysis of genotype-by-environment (GE) interaction on 20 durum wheat genotypes grown in 15 testing environments during 2004–06 in Iran. Combined analysis of variance showed significant genotypes (G), environments (E), and GE interactions (P < 0.01), with environmental main effects being the predominant source of variation, followed by GE interaction. The results showed various patterns of genotype responses to different environment groups and assisted in structuring the durum wheat testing locations with identification of two major-environment groups with high genotype discrimination ability. The locations (Gachsaran and Ilam) corresponding to warm and semi-arid aresa were similar in genotype discrimination and showed no association with the other testing locations (Gonbad, Moghan, and Khoramabad) representing the Mediterranean area, indicating they differ in rankings of genotypes. The top-yielding genotypes, G13, G14 and G9, were highly adapted to warm and semi-arid environments, but those corresponding to the Mediterranean area had a high ability to discriminate the genotypes G16, G11, and Saimareh. The stability and adaptability of specific genotypes were assessed by plotting their nominal grain yields at specific environments in an ordination biplot, which aided in the identification of environment groups. Appropriate check genotypes for all environments or for specific environments were also identified. Pattern analysis allowed a sensible and useful summarization of GE interaction data set and helped to facilitate selecting superior genotypes for target-growing sites.     

Specific adaptation and breeding for marginal conditions

Summary Breeding has been very successful in generating cultivars that in favorable environments, and together with large use of fertilizer and chemical control of weeds, pest and diseases, have increased agricultural production several fold. Today the environmental impact of high input agriculture in more favorable environments causes growing concern. By contrast, the impact of breeding in marginal environments has been elusive. The paper discusses evidence showing that the use of breeding principles developed for, and successfully applied, in favorable environments may be the main reason for the lack of breeding progress in marginal environments. Very little breeding work has actually been done in marginal environments, although the theory of correlated responses to selection indicates that selection conducted in good environments or in well-managed experiment stations is not expected to be very efficient when genotype by environment interactions of a cross-over type exist. The assumptions that heritability is higher under good conditions and that there is a carry-over effect of high yield potential are not supported by experimental evidence. If the target environment is below the cross-over point, selection has to be conducted for specific adaptation to that environment. The concept of wide adaptation has more a geographical than an environmental meaning, and it reduces genetic diversity and increases genetic vulnerability. Eventually the issue of genetic heterogeneity versus genetic uniformity is discussed in relation to specific adaptation to marginal environments.     

Estimate of genotypic value: A proposed method

Summary Genotypic differences in yield between breeding lines or cultivars may be estimated with the aid of functions of the regression of their individual yields, in different environments, on the mean yields of all the lines tested in the respective environments.     

Associations between nitrogen harvest index and yield characteristics of oats

Summary Fifty lines of oats (Avena Sativa L.) with a broad range of nitrogen harvest indexes (NHI) and nine check lines were evaluated in 15 environments to study the association between NHI and adaptability of oat lines to soils with different productivity levels due primarily to different amounts of N. Three yield characteristics (i.e., mean across environments, regression response to improving environments, and stability of response) were used to measure adaptability. The lines were significantly variable for means of grain and straw yield, for responsiveness to improving environments, and for stability of yield. Among the yield characteristics, only the mean of grain yield was significantly correlated with NHI.Journal Paper No. J-13336 of the Iowa Agric. and Home Econ. Exp. Stn., Ames, Iowa, 50011. Project 2447.     

Identification of quantitative trait loci (QTLs) for seed protein concentration in soybean and analysis for additive effects and epistatic effects of QTLs under multiple environments

Soybean protein concentration is a key trait driver of successful soybean quality. A recombination inbred lines derived from a cross between ‘Charleston’ and ‘Dongnong594’, were planted in three environments across four years in China. Then, the genetic effects were partitioned into additive main effects, epistatic main effects and their environment interaction effects by using composite interval mapping, multiple interval mapping and composite interval mapping in a mixed linear model. Forty‐three quantitative trait loci QTLs were identified on 17 of 20 soybean chromosomes excluding Ch 7, Ch 8 and Ch 17. Two QTLs showed a good stability across multiple environments, qPRO20‐1 was detected under four environments, which explained 4.4–9.95% phenotypic variances and the allele was from ‘Charleston’ among four environments. qPRO7‐5 was detected under three environments, which explained 7.2–14.5% phenotypic variances and the allele was from ‘Dongnong 594’, three pathway genes of protein biosynthesis were detected in the interval of qPRO7‐5. The additive main‐effect QTLs contributed more phenotypic variation than the epistasis and environmental interaction. This indicated that it is feasible by marker‐assisted selection to improve soybean protein concentration.