ABADIE, T.

ANDRADE, R. V. de

CORDEIRO, C.

MAGALHAES, J. R.

PARENTONI, S. N.

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Country ReportsA Core Subsetof Brazilian Maize GermplasmTabare Abadie'; 'R.amiro V. ae71.nâra e Celia Cordeiro], José R. Magalhaes', Sidney N Parell!oni]1 Facultad de Agronomía, GarzQ 78'0, Montevideo, Uruguay, tabadie@inia.org.uy;2 Centro Nacional de Pesquisa de Milho e Sorgo-EMBRAPA,C. Postal 151-35701-970, Sete Lagoas, MG, Brazil;) Centro Nacional de Recursos Genéticos e Biotecnología-EMBRAPA,SAIN-70.770-900, Brasilia, DF, Brazil,The Brazilian maize germplasm collection comprises 2,263 accessions that have adequate passport dataand are currently conserved at the Centro Nacional de Recursos Genéticos (CENARGEN-EMBRAPA),and the Centro Nacional de Pesquisa de Milho e Sorgo (CNPMS-EMBRAPA). The objective ofthisresearch was to develop a core collection ofthe collection to facilitate its use by breeding programs. Thesubset and related research was developed by an interdisciplinary group of curators, breeders, andstatisticians.Developing a core collection is basically a sampling excercise. The two main problems to solve are thesize of the sample and the sampling strategy to be used. In our case, 300 accessions were considered anadequate sample size. This represents 13% ofthe base collection, which is more than the 10% limitrecommended by Brown (1989). In addition, 300 is a number of accessions that can be handled withrelative low cost by the curator.A two-level sampling strategy was used. At the first levei, the accessions were classified into three strataaccording to origin ofthe germplasm: 1) landraces (1,753 accessions); 2) improved materiais (222accessions); and 3) introductions (288 acccessions). Each stratum was proportionately represented in thecore collection.At the second level, specific sub-classifications were used within each stratum. Landraces were cIassifiedin 27 groups, based on ecogeographical origin and grain type (Table 1), as suggested by Abadie et a!.(1997). The ecogeographical regions used in this case were the same as those used by Cordeiro et a!.(1995) for the cIassification ofBrazilian cassava accessions. A logarithmic strategy was used to assign theproportional representation of each group in the core collection. Within each group, the accessions wereselected by the curators taking into account their experience and knowledge ofthe crop when possible, orotherwise at random.The improved materiais were classified as pops (pop maize), non-pops from C1\'PMS, And non-pops fromother breeding programs. This cIassification followed from the principal components analysis done on thedata ofFeldman and Silva (1984), following the methodology used by Abadie et a!. (1997) in the study ofthe landraces. The introductions were classified based on their origin as tropical or temperate, and withineach ofthese groups based on the four main grain types (pop, flint, floury, dent), as suggested by the23experience of the curators and breeders. The representation of each group of the latter two strata wasproportional to their size. The core coIlection samples belonging to each group were selected by thebreeders rrvmg ,0 -naintam maximum genetic variation and to include those accessions representative ofthe main genetic pools used m the breeding programs.The development of this maize core coIlection has resulted in a new classification of the Brazilian maizecolIection, based on experimental results (Abadie et aI. 1997) and on the knowledge and experience ofcurators and breeders. In addition, the classification was developed using available passport andcharacterization data, without the need for additional expensive research. The appeal of the newclassification system is both its simplicity and its intuitively sound biological and practical basis. Weexpect that this wiII encourage breeders to use Brazilian maize germplasm in their programs.Acknowledgement oTo Dr. Emesto Patemiani for his valuable cornrnents and suggestions during the deveIopment of thisresearch.ReferencesAbadie, T., J.R. Magalhaes, C. Cordeiro, S. Parentoni, and R. de Andrade. 1997. Obtençao e tratamientoanalítico de dados para organizar Coleçcao Nuclear de milho. EMBRAPA, Comunicado TécnicoN"20, Outubro/97, p 1-7.Brown, A.H.D. 1989. The case for core colIections. In A.H.D. Brown, O.H. Frankel, D.R. MarshalI, andJ.R. WilIiams (eds.). The Use of Plant Genetic Resources, 136-156. Cambridge: CambridgeUniversity Press.Cordeiro, C.M.T., E.A.V. Morales, P. Ferreira, D.M.S. Rocha, I.R.S. Costa, A.C.c. Valois, and S. Silva.1995. Towards a Brazilian core colIection of cassava. In T. Hodgkin, A.H.D. Brown, T.J.L. vanHintum, and E.A.V. Morales (eds), Core Collections ofPlant Genetic Resources, 155-167. NewYork: John Wiley & Sons.Feldman, R., and J. Silva. 1984. Catalogo de germoplasma de milho, Zea mays L. EMBRAPACENARGEN, Brasilia DF.Table 1. Distribution of Brazilian landraces based on grain type and ecogeographical region oforigin, in the base collection (BC) and core collection (CC).FlouryPop Flint and other DentOrigin BC CC BC CC SC CC BC CCSouth 29 10 23 9 5 5 279 17Cerrados 26 10 77 13 50 12 321 19Cerrados North 12 8 9 7 6 5 110 14Amazonia 35 12 94 15 19 8 121 14Caatinga 17 8 38 11 1 1 169 16Agreste Litoral 1 I 14 8 O O 62 12Non-class 4 O 5 O 7 O 10 OLandraces in lhe CC = 235.24

A core subset of Brazilian maize germplasm.

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A core subset of Brazilian maize germplasm.

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