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Phenotypic diversity of 101 durum wheat landrace populations collected from the oasis of the Oriental Atlas Mountains (Morocco) was studied. Nine characters (morphological and agronomic) were measured on the 3030 lines (30 lines per population). The frequencies of each phenotypic class were used for the estimate and the analysis of diversity, by considering the geographical zones of origin and the gradients of altitude. The Shannon-Weaver diversity index (H’) showed a wide variability for all considered traits. This index varies from one area to another and from one altitudinal class to another. The mean H’ recorded for all areas was 0.62, indicating the presence of a high degree of polymorphism among the studied durum wheat landrace populations. The results of the multiple component analysis and the hierarchical clustering showed that the geographical proximity and altitude play a main function in the discrimination and the structure of the studied durum wheat populations. The information gathered from this study could be used in conventional breeding programs and in situ conservation of the diversity.

La diversité phénotypique de 101 populations locales de blé dur issues des oasis de montagnes de l’Atlas oriental (Maroc) a été étudiée. Neuf caractères (morphologiques et agronomiques) ont été mesurés sur les 3030 lignées (30 lignées par population). Les fréquences de chaque classe phénotypique ont été utilisées pour l’estimation et l’analyse de la diversité, en considérant les zones géographiques d’origine et les gradients d’altitude. L’indice de diversité de Shannon-Weaver (H’) a montré une forte variabilité pour l’ensemble des caractères considérés. Cet indice varie d’une zone à une autre et d’une classe d’altitude à une autre. Le H’ moyen obtenu pour l’ensemble des zones est de 0,62, indiquant la présence d’un degré élevé de polymorphisme au sein des populations locales de blé dur collectées. Les résultats de l’analyse en composantes multiples ainsi que de la classification hiérarchique ont montré que la proximité géographique et l’altitude jouent un rôle majeur dans la discrimination ainsi que sur la structuration des populations de blé dur étudiées. Les informations recueillies à partir de ces résultats peuvent être exploitées dans des programmes de sélection conventionnels et de conservation in situ de la diversité. Mots clés: Populations locales, diversité phénotypique, structuration, conservation in situ, blé dur (Triticum turgidum ssp. durum).

Abstract Variety mixtures, the cultivation of different genotypes within a field, have been proposed as a way to increase within‐crop diversity, allowing the development of more sustainable agricultural systems with reduced environmental costs. Although mixtures have often been shown to over‐yield the average of component varieties in pure stands, decreased yields in mixtures have also been documented. Kin selection may explain such pattern, whenever plants direct helping behaviors preferentially toward relatives and thus experience stronger competition when grown with less related neighbors, lowering seed production of mixtures. Using varieties of durum wheat originating from traditional Moroccan agrosystems, we designed a greenhouse experiment to address whether plants reduced competition for light by limiting stem elongation when growing with kin and whether such phenotypic response resulted in higher yield of kin groups. Seeds were sown in groups of siblings and nonkin, each group containing a focal plant surrounded by four neighbors. At the group level, mean plant height and yield did not depend upon relatedness among competing plants. At the individual level, plant height was not affected by genetic relatedness to neighbors, after accounting for direct genetic effects that might induce among‐genotype differences in the ability to capture resources that do not depend on relatedness. Moreover, in contrast to our predictions, shorter plants had lower inclusive fitness. Phenotypic plasticity in height was very limited in response to neighbor genotypes. This suggests that human selection in crops may have attenuated shade‐avoidance responses to competition for light. Future research on preferential helping to relatives in crops might thus target social traits that drive competition for other resources than light. Overall, our study illustrates the relevance of tackling agricultural issues from an evolutionary standpoint and calls for extending such approaches to a larger set of crop species.

Durum wheat is a strategic crop in Morocco. Characterization and evaluation of cultivated varieties in different traditional agroecosystems allows safeguard and rehabilitation of this genetic heritage and its use in breeding programs. In this context, a collection of 59 traditional populations of durum wheat from the Pre-Rif region was studied using nine agro-morphological traits. Phenotypic diversity was determined by the Shannon-Weaver diversity index (H’) at different levels (totality of sample, by type of wheat and varietal names). Estimated H’ showed a wide genetic variability for different traits with a mean of H’=0.78. The results of the multiple correspondence analysis and hierarchical clustering showed a clear distinction between modern and traditional varieties. In traditional varieties, agro-morphological traits do not differentiate between varieties. The results of this work revealed the great phenotypic and nominative diversity of durum wheat varieties as well as the existence of homonyms and synonyms in the names given by farmers.