Julien Berthaud

Participatory landrace selection for on-farm conservation: an example from the central valleys of Oaxaca México

On-farm conservation is recognized as a key component of a comprehensive strategy to conserve crop genetic resources. A fundamental problem faced by any on-farm conservation project is the identification of crop populations on which efforts should be focused. This paper describes a method to identify a subset of landraces for further conservation efforts from a larger collection representing the diversity found in the Central Valleys of Oaxaca, Mexico. Mexico is a center of origin and diversity for maize (Zea mays L.). The 17 landraces selected from an initial collection of 152 satisfy two criteria. First, they represent the diversity present in the larger collection. Second, they appear to serve the interests of farmers in the region. Data for applying the method were elicited through participatory as well as conventional techniques. They incorporate the complementary perspectives of both men and women members of farm households, and of plant breeders and social scientists.

Transgenic maize and the evolution of landrace diversity in Mexico. The importance of farmers' behavior

The discovery of transgenic products in maize ( Zea mays ) landraces planted by small-scale Mexican farmers (Quist and Chapela, [2001][1], [2002][2]; [Christou, 2002][3]; [Editorial Note, 2002][4]) raised questions about how the commercial introduction of transgenic maize varieties might affect the

Genetic Nature of Yams (Dioscorea sp.) Domesticated by Farmers in Benin (West Africa)

Abstract‘Domestication’ is a traditional farmers’ practice reported for yams (Dioscorea sp.) in Benin (West Africa). It involves introducing ‘spontaneous’ (naturally occurring) yams, supposedly wild (D. abyssinica and D. praehensilis), in varieties of the D. cayenensis–D. rotundata cultivated species complex. In this study, we established the genetic nature of ‘predomesticated’ yam plants using the amplified fragment length polymorphism (AFLP) technique. A total of 213 accessions, consisting of 32 predomesticated yams, 70 D. cayenensis–D. rotundata, 86 D. abyssinica and 25 D. praehensilis yams were analysed. Using 91 AFLP markers, three groups of accessions were distinguished, broadly corresponding to the above botanical species. Of the 32 predomesticated accessions, 16% were clustered with D. praehensilis, 37% with D. abyssinica and the remaining 47% with D. cayenensis–D. rotundata. These results demonstrated the use of wild plants by farmers in their domestication process, and suggested that plants derived from intervarietal and interspecific hybridisation may also be subject to this process. This study has shown that through domestication farmers influence and increase the genetic diversity in yam by using sexual reproduction of wild and possibly cultivated yams.

Genetic diversity and relationship in American and African oil palm as revealed by RFLP and AFLP molecular markers

Abstract – The objective of this work was to evaluate the genetic diversity, its organization and thegenetic relationships within oil palm ( Elaeis oleifera (Kunth) Cortes, from America, and E. guineensis(Jacq.), from Africa) germplasm using Restriction Fragment Length Polymorphism (RFLP) and AmplifiedFragment Length Polymorphism (AFLP). In complement to a previous RFLP study on 241 E. oleiferaaccessions, 38 E. guineensis accessions were analyzed using the same 37 cDNA probes. These accessionscovered a large part of the geographical distribution areas of these species in America and Africa. Inaddition, AFLP analysis was performed on a sub-set of 40 accessions of E. oleifera and 22 of E. guineensisusing three pairs of enzyme/primer combinations. Data were subjected to Factorial Analysis ofCorrespondence (FAC) and cluster analysis, with parameters of genetic diversity being also studied.Results appeared congruent between RFLP and AFLP. In the E. oleifera, AFLP confirmed the strongstructure of genetic diversity revealed by RFLP, according to geographical origin of the studied material,with the identification of the same four distinct genetic groups: Brazil, French Guyana/Surinam, Peru,north of Colombia/Central America. Both markers revealed that genetic divergence between the twospecies is of the same magnitude as that among provenances of E. oleifera. This finding is in discrepancywith the supposed early tertiary separation of the two species.Index terms: Elaeis oleifera, Elaeis guineensis, population genetics, palm species, genetic resources,molecular chacterization.Diversidade e relacao genetica entre o dende americano e o africanorevelada por marcadores moleculares do tipo RFLP e AFLPResumo – O objetivo deste trabalho foi avaliar a diversidade genetica, sua organizacao e a relacaogenetica no germoplasma de dende ( Elaeis oleifera (Kunth) Cortes, de origem americana, e E. guineensis(Jacq.), africana), pelas tecnicas de Polimorfismo de Comprimento de Fragmentos de Restricao (RestrictionFragment Length Polymorphism – RFLP) e Polimorfismo de Comprimento de Fragmentos Amplificados(Amplified Fragment Length Polymorphism – AFLP). Em complemento a um estudo previo de RFLPem 241 acessos de E. oleifera, 38 acessos de E. guineensis foram analisados usando as mesmas 37sondas de cDNA. Os acessos estudados cobrem uma grande parte da area de distribuicao geograficadestas duas especies nos continentes Americano e Africano, respectivamente. Alem disso, analises commarcadores AFLP foram realizadas em uma subamostra com 40 acessos de E. oleifera e 22 de E. guineensis,empregando tres combinacoes de pares enzima/primer. Os dados foram submetidos a analise fatorial decorrespondencia (AFC) e analise de cluster, sendo tambem estimados parâmetros de diversidade genetica.Os resultados obtidos apresentaram grande coerencia entre as duas tecnicas utilizadas, RFLP e AFLP.Na especie E. oleifera, a tecnica AFLP confirmou a forte estruturacao da diversidade genetica reveladapela tecnica de RFLP, de acordo com a origem geografica do material estudado e com a identificacao dosmesmos quatro grupos geneticos distintos: Brasil, Guiana Francesa/Suriname, Peru e norte da Colombia/America Central. Entretanto, ambos os marcadores revelaram que a divergencia entre as duas especiese da mesma magnitude da divergencia dentro da especie americana. Este resultado esta em discrepânciacom uma suposta separacao das duas especies durante a era terciaria.Termos para indexacao: Elaeis oleifera , Elaeis guineensis , genetica de populacao, palmeiras, recursosgeneticos, caracterizacao molecular.

Genetic diversity analysis of yam cultivars (Dioscorea rotundata Poir.) in Benin using simple sequence repeat (SSR) markers

Abstract Guinea yam (Dioscorea rotundata Poir.) is a dioecious vegetatively propagated tuber crop. It iswidely cultivated by traditional techniques in West Africa, its area of origin. The genetic diver-sity of 146 accessions from Benin was analysed using 10 polymorphic simple sequence repeat(SSR) nuclear markers and agromorphological traits. An average of 8.4 alleles per locus wasdetected. The mean heterozygosity was 0.57 and the mean polymorphism information content(PIC) for polymorphic markers was 0.51. Some cultivars (23%) were found to have an identicalgenotype for the 10 markers. The structure of the genetic diversity observed in Benin is theresult of farmers’ crop management practices and their know-how. The cultivar diversityhad a geographical component. We also noted major differentiation between early and latecultivars, with higher diversity in the early ones. Cultivars from northern Benin and early cul-tivars had the greatest allelic richness. SSR markers proved to be powerful tools for fingerprint-ing each cultivar and analysing their genetic relationships. The results of this study could beuseful for defining a strategy for the conservation of genetic diversity in yams.