Multi-Environment Evaluation and Genetic Characterisation of Common Bean Breeding Lines for Organic Farming Systems

Abstract

It is recognised that one of the main causes for the relative low yields under organic conditions is the use of modern cultivars which are bred for high-input management systems. The work described here aimed to study and test possible breeding strategies to produce cultivars of common bean for organic agriculture. To this purpose, crosses between a traditional Italian landrace named "Gnocchetto" and a cultivar were carried out. The F 1 plants obtained were either backcrossed or self-fertilised and the obtained materials subjected to selection for quality traits at different development stages. The resulting lines were tested under four different environmental conditions for three years in order to determine their potential performance. The resulting data were analysed using a Multi-Environment Trial Analysis (MET) approach and different visualisations of the GGE biplot were generated. Furthermore, to assess the level of genetic similarity, the lines were characterised using 25 Simple Sequence Repeat (SSR) molecular markers. Results showed that the breeding approach applied allowed to select lines with the same technological and agronomic characteristics as commercially available cultivars, but with different adaptation abilities that make them suitable for organic agriculture.Sustainability 2018, 10, 777 2 of 17 hand, Seufert and colleagues [13] showed that yield differences between organic and conventional agriculture do exist, but that they are highly contextual, depending on the system, site characteristics and crop types. Moreover, Ponisio et al. [14] built a hierarchical meta-analytic model to better dissect and estimate the yield gap between the two management systems. They found that organic yields are, on average, 19.2% (±3.7%) lower than conventional, while, in contrast to the previous studies, their results demonstrated a lack of significant differences in yield gaps for leguminous versus non-leguminous crops and perennials versus annuals; even more interestingly, results showed that agricultural diversification practices such as rotations or multi-cropping can reduce the yield gap between the two management systems.It has been suggested that one of the main causes for the low yields achievable under organic conditions is the use of modern cultivars which are bred for high-input production systems [15,16]. Currently, most cultivars are specifically bred for conventional agriculture and rely on the use of pesticides and fertilisers for optimal performance [14,17,18]. Nevertheless, there is also evidence that conventionally bred cultivars do not always perform worse than those bred for organic agriculture when tested under organic conditions; for example, genotype by system interactions were not reported in studies carried out on wheat [19] or oats [20]. In comparative trials of 32 dry bean genotypes under organic versus conventional systems, Heiling and Kelly [21] reported that some genotypes were better suited for organic production than others. However, those genotypes poorly performing under organic...

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