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CROP BREEDING, GENETICS & CYTOLOGY

Defining Subregions and Estimating Benefits for a Specific-Adaptation Strategy by Breeding Programs

A Case Study

^a Istituto Sperimentale per le Colture Foraggere, 29 viale Piacenza, 26900 Lodi, Italy
^b Institut Technique des Grandes Cultures, BP 16, El-Harrach, Alger, Algeria
^c Istituto Agronomico per l'Oltremare, 4 via A. Cocchi, 50131 Florence, Italy

^* Corresponding author (bred{at}iscf.it)

Producing specific varieties for each subregion of a target region, instead of widely adapted varieties, may exploit positive genotype x location (GL) interactions to increase crop yields. With reference to the Algerian durum wheat (Triticum durum Desf.) region, as defined in a Geographic Information System (GIS), this study aimed at (i) comparing additive main effects and multiplicative interaction (AMMI) vs. joint regression modeling of GL effects, (ii) verifying the reliability of a GIS-based definition of two subregions that extended the site classification on the basis of GL effects as a function of long-term winter mean temperature in the GIS, and (iii) comparing wide vs. specific adaptation in terms of observed and predicted yield gains (the latter for scenarios of defined and undefined selection locations). Twenty-four cultivars from international centers, Europe, and North Africa were evaluated across 3 yr in a total of 47 environments by randomized complete block designs with four replications per trial. The AMMI modeling was distinctly superior to joint regression. The AMMI + cluster analysis and pattern analysis classified test locations consistently and in good agreement with the GIS-based subregion definition. Under the hypothesis of six selection environments assigned to subregions in proportion to their size (three sites in each of two years) for late stage selection, specific adaptation provided 2 to 7% greater gains than wide adaptation over the region at similar costs. The advantage of specific adaptation was much larger (39% determined on the basis of observed gains) for the smaller, stressful inland subregion, where specific adaptation may also enhance food security. Performing earlier specific selection, or adopting distinct genetic bases for each subregion, may further increase the advantage of specific breeding.

Abbreviations: AMMI, additive main effects and multiplicative interaction • ANOVA, analysis of variance • CIMMYT, Centro Internacional de Mejoramiento de Maiz y Trigo • GE, genotype x environment • GIS, Geographic Information System • GL, genotype x location • GY, genotype x year • ICARDA, International Center for Agricultural Research in the Dry Areas • PC, principal component

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Crop Science 2005 45: x. [Full Text]  

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