Geographical Patterns of Phenotypic Diversity in a World Collection of Durum Wheats¹

Abstract

More than 3,000 durum wheats ( Triticum turgidum L. durum group) from the USDA world wheat collection were grown in the field and classified for leaf sheath glossiness, glume pubescence and color, awn color, kernel color, and basal spike node fertility. The entries were grouped by geographic origin, and frequencies of the various phenotypes were examined. Variation for all characters was found, and usually within each geographic region. The number of entries in the collection was very small from some areas known to be important sources of germplasm, pointing to the importance of intensifying efforts in germplasm exploration and conservation. The Shannon‐Weaver diversity index (H') was used to examine overall genetic divergence on a country and regional basis. In collections of substantial size, Ethiopia and Portugal had the greatest diversity (H' = 0.87 and 0.86), and Turkey, Bulgaria, and the United States had significantly less diversity (H' = 0.50, 0.42, and 0.39). Based on the characters studied and the relatively small collection evaluated, the centers of diversity seem to be Ethiopia, the Mediterranean region, and India.