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

The results from multienvironment field performance trials of cultivars are usually analysed as two‐way classification data with rows=genotypes/cultivars and columns=environments (locations and/or years). To reduce the impact of genotype × environment interaction effects, one commonly stratifies genotypes/cultivars or environments by cluster analysis techniques into homogeneous groups so that interactions within groups are minimized. By such a stratification, for example of test sites, with regard to similarity of genotype × environment interactions and the selection of only one representative test site from each group, the overall number of necessary test sites for yield trials can be reduced. In the literature, many clustering techniques have been proposed. Systematic comparisons between different cluster methods, however, are rather rare. A single cluster method is characterized by `measure of distance', `stopping criterion', `algorithm' and `level of significance'. In this paper, 11 clustering techniques were applied to extensive yield data sets of several agricultural crops (faba bean, fodder beet, oat, winter oilseed rape and sugar beet) from the official registration trials of the German `Bundessortenamt'. The results were compared with each other using two proposed parameters: measure of resemblance (for two classifications) and cluster size (for one classification). Neither the level of significance nor the algorithm has a substantial impact on the resulting clusters. The final results of clustering are therefore mainly determined by the stopping criterion with its associated measure of distance. If one uses tests for crossover interactions as stopping criteria, the resulting clusters are larger than the resulting clusters for the F‐test of conventional interactions in an analysis of variance. The cluster size decreases with increasing sensitivity of the tests that are used as stopping criteria. Finally, recommendations for the choice and handling of clustering techniques for practical applications are given.     

Contributions to the Analysis of Genotype × Environment Interactions: Comparison of Different Parametric and Non-parametric Tests for Interactions with Emphasis on Crossover Interactions

The objective of this study was to compare five statistical procedures (analysis of variance, the Azzalini/Cox test, the Hildebrand procedure, the Kubinger approach, and the de Kroon/van der Laan technique) for the analysis of genotype × environment interactions in cross‐classified data sets from cultivar performance yield trials with rows = cultivars and columns = environments (locations and/or years). The procedures Hildebrand, Kubinger and de Kroon/van der Laan are non‐parametric methods based on ranks, while analysis of variance and the Azzalini/Cox test proceed from the original absolute yield data. These very different statistical techniques were applied to extensive data sets from German official registration trials (1985–1989) with winter oilseed rape (Brassica napus L.), faba bean (Vicia faba L.), oat (Avena sativa L.), fodder beet (Beta vulgaris L.) and sugar beet (Beta vulgaris L.). The Azzalini/Cox and de Kroon/van der Laan methods are based on the crossover concept of interaction (different rank orders) while the other methods are based on the usual concept of interaction (deviations from additivity of main effects). For an analysis of usual interactions the procedures Hildebrand, Kubinger and analysis of variance are approximately equivalent. For the crossover concept of interaction, the Azzalini/Cox approach is recommended, especially if one is particularly interested in rank changes between environments within genotypes.     

Evaluation of Genotype × Environment Interactions in Chinese Spring Wheat by the AMMI Model, Correlation and Path Analysis

An understanding of the characteristics of crop varieties and advanced lines could help improve their cultivation and to further enhance their potential. The objectives of this study were to estimate the genotype (G), environment (E) and genotype × environment (GE) interactions on the grain yield of Chinese spring wheat genotypes in 2000 and 2001 by the additive main effects and multiplicative interaction (AMMI) model, and to evaluate the relationships between yield and its components by correlation and path analysis. Grain yield varied from 3.9 to 5.2 t ha^?1, among which SW8188 had the highest yield performance, followed by 58769‐6 and Chuannong 16. Three interaction principal components (IPC) accounted for a total of 79.99 % and 72.96 % of the interactions with 41.05 % and 52.08 % for the corresponding degrees of freedom in 2000 and 2001, respectively. When IPC3 was significant, the stability coefficient D_i was more useful in the evaluation of the stability of each genotype. The estimates of D_i in the 2 years indicated that the D_i values varied between genotypes and years. The D_i values ranged from 1.804 to 14.665 and 2.497 to 12.481 in 2000 and 2001 respectively. The suitable locations (environments) for all genotypes were characterized. These results would be useful for improving the Chinese spring wheat cultivation and improvement.     

2010—2011年北京农资流通领域中肥料产品质量抽检结果的分析评价与建议

为了了解2010—2011年北京市农资流通领域中肥料产品质量的动态变化状况,通过对北京市农资市场肥料产品进行抽检的方法,得出了相应的检测数据并对抽检结果进行了分析与评价。结果表明,2年来北京市农资流通领域的肥料质量总体呈现良好态势。无机肥料的种类和流通量均在肥料市场上占有主导地位,有机肥料和有机—无机复混肥料的市场占有率均较低。北京市肥料产品的主要问题主要表现在单一养分含量不足及有害元素含量超标两方面上。