CROPS AND SOILS RESEARCH PAPER Evolution of a barley composite cross-derived population: an insight gained by molecular markers L. RAGGI 1 , S. CECCARELLI 2 AND V. NEGRI 1 * 1 Dipartimento di Scienze Agrarie, Alimentari e Ambientali, Università degli Studi di Perugia, Borgo XX Giugno 74, 06121 Perugia, Italy 2 ICARDA, P.O. Box 114/5055, Beirut, Lebanon / 2 Via delle Begonie 2, 63100 Ascoli Piceno, Italy (Received 10 February 2014; revised 20 October 2014; accepted 24 November 2014) SUMMARY Many studies have highlighted the continuously increasing need for genetic diversity in the field; nonetheless, plant breeding is still predominantly generating uniform cultivars. Evolutionary plant breeding offers the possi- bility of reconciling agro-biodiversity, high yields and adaptation to climate change. However, the diversity that can be conserved in heterogeneous populations, its evolution and the potential of ‘evolutionary breeding’ in the actual scenario of climate change is still a matter of debate. In the present study, a total of 147 barley indi- viduals, 56 from seven parental populations (PPs) and 91 from the composite cross-derived population (CCP) resulting from their inter-crossing were genotyped at 22 Simple Sequence Repeat (SSR) loci with the objective of obtaining insights into how genetic diversity evolved in the field during 13 years of multiplication. A total of 92 different alleles were detected in the PP and 100 in the CCP. Results showed that the composite individuals are grouped into five major clusters differing for both the number of individuals and the relative level of genetic diversity. The mean values of the most common descriptors of genetic diversity were not significantly different between the parental and the composite populations. However, analysis of molecular variance showed some degree of differentiation between the two populations suggesting that evolution occurred during the years of mul- tiplication and selection effects were detected for some loci. The SSR loci detected as putatively under selection in the present study have already been reported as co-localized with quantitative trait loci for adaptedness traits or tagging genes related to abiotic stress response. According to the current results, evolving crop populations, which have the capability of adapting to the conditions under which they are grown, can be useful in conserving genetic diversity and as sources of genes for breeding purposes in particular in the actual scenario of climate change. INTRODUCTION The importance of biodiversity and the dangers associ- ated with its decline are frequently emphasized (Cardinale et al. 2012; Hooper et al. 2012), as is the vulnerability of crops associated with the continuous decline of diversity in the field (Esquinas-Alcázar 2005; Hajjar & Hodgkin 2007; Keneni et al. 2012). This is in open contrast with the tendency of modern plant breeding towards producing uniform varieties (Ceccarelli et al. 2013). This contradiction appears even more striking when the likely scenario of climate change is considered. Climate change poses an interesting challenge to plant breeders because, contrary to the usual target objectives of a breeding programme, it represents a ‘moving target’ (Ceccarelli et al. 2013). A strategy to cope with such a challenge, which could also maintain and increase agricultural biodiversity, is evolutionary plant breeding. The idea is not new. In 1929, Harlan and Martini proposed the composite cross (CC) method for breed- ing barley (Harlan & Martini 1929). The method relies on bulking the F1 progenies obtained by hybridization of varieties of diverse origin and genetic make-up to generate a heterogeneous population of recombinant * To whom all correspondence should be addressed. Email: valeria.negri@unipg.it Journal of Agricultural Science, Page 1 of 17. © Cambridge University Press 2015 doi:10.1017/S0021859614001269