-1 Differentiation among maize (Zea mays L.) landraces from the Tarasca Mountain Chain, Michoacan, Mexico and the Chalquen ˜o complex Javier O. Mijangos-Corte´s 1,2, *, T. Corona-Torres 1 , D. Espinosa-Victoria 1 , A. Mun˜oz-Orozco 3 , J. Romero-Pen˜aloza 3 and A. Santacruz-Varela 1 1 Campus Montecillo, Colegio de Postgraduados, km 36.5 Carr. Me´xico-Texcoco, CP 56230, Montecillo, Texcoco, Edo. de Me´xico, Me´xico; 2 Unidad de Biotecnologı´a, Centro de Investigacio ´n Cientı´fica de Yucata ´n A.C., Calle 43 # 130 Colonia Chuburna ´ de Hidalgo, C.P. 97200, Me´rida, Yucata ´n, Me´xico; 3 Centro Regional Universitario del Centro Occidente, Universidad Auto ´noma Chapingo; *Author for correspondence (e-mail: jomijangos@yahoo.com.mx) Received 31 January 2005; accepted in revised form 28 October 2005 Key words: Isozymes, Maize race, Phenetic relations, Tarasca Mountain Chain, Zea mays L. Abstract The classification of Mexican maize (Zea mays L.) begun since the early 20th century, it was consolidated during the middle of this century, but recent additions and rearrangements have been performed by several authors employing new methods of analysis and collections from diverse origin; nevertheless, maize from the State of Michoacan, Mexico has received little attention in regard to its systematic classification. Maize populations from the Tarasca Mountain Chain in Michoacan are commonly considered in literature, as belonging to the Chalquen ˜o race; however, closer observations indicate that significant differences do exist, suggesting the necessity of performing an in-depth study on this respect. Thirty nine native maize popu- lations from the Tarasca Mountain Chain region were evaluated along with 19 typical populations of the Chalquen ˜o, Celaya and Conico races coming from the States of Mexico, Puebla, Hidalgo, Quere´taro and Oaxaca. Populations were evaluated in Aranza, Michoacan and Montecillo, Mexico State. Seventeen morphological characters were scored and analyzed by one-way analyses of variance and multivariate techniques. Populations were also genetically analyzed through 17 isozyme loci. Native populations had some alleles not found either in the Chalquen ˜o, Celaya or Conico races, and possess larger genetic diversity. Local populations were congregated into a discrete group apart from the typical Chalquen ˜o populations, suggesting that landraces from the Tarasca Mountain Chain region might not be considered as belonging to the Chalquen ˜o race, but they integrate by themselves a different race. Introduction Maize genetic diversity in Mexico is explained by some factors as: (1) the geography with lots of microregions or ‘ecological niches’ throughout the country, with irregular orography and characterized by particular climatic and edaphic conditions dif- fering from each other; thus, specific maize variants must be adapted to every ecological niche (Mun˜oz 2003), and (2) ethnic groups that have selected for different uses and preserved the adequate kind of maize for their particular environments according to their own customs, knowledge, management prac- tices and traditions (Herna´ndez and Alanis 1970). Mun˜oz et al. (2003) mentioned that in Mexico the diversity of native maize populations is finely Genetic Resources and Crop Evolution (2007) 54:309–325 Ó Springer 2006 DOI 10.1007/s10722-005-4775-y