, Volume 48, Issue 4, pp 381-390

Sampling strategy to develop a core collection of Uruguayan maize landraces based on morphological traits

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Abstract

Core collections were suggested to improve germplasmutilization. A core collection is a subset chosen to represent thediversity of a collection with a minimum of redundancies. Becausediversity is distributed between and within groups with differentdegrees of organization, an adequate classification of accessionsinto related groups should be performed prior to the selection of acore collection. Different classification strategies for theUruguayan Maize Collection were compared, and the best one was usedto select a core collection. The following classification strategieswere compared following a multivariate approach using the availablemaize data base: i) racial classification, ii) geographicorigin (south and north of the country), and iii) acombination of kernel type and geographic origin. The third optionwas considered the best classification rule, since it takes intoaccount two points which are closely related to the distribution ofdiversity: genotypic composition and geographic origin. The followingfive groups were identified in the collection: a) pop, b)floury, c) dent, d) southern flint-semiflints, ande) northern flint-semiflints. Eight core collections,each of 90 accessions, were selected, using different strategies toweight the groups in the core and to select the accessions from thegroups. The P, C, and L strategies were used and combined with eitherrandom selection within the group or the Relative Diversity method.Two samples of 90 accessions were obtained at random withoutconsidering the classification. The Relative Diversity methodcombined with the L strategy produced the best core collection, as itretained the highest percentage of the ranges for the 17 variablesincluded in the analysis. On average, 91% of the ranges wereretained in the core, confirming its representativeness.