Euphytica 95: 361–369, 1997. 361 c 1997 Kluwer Academic Publishers. Printed in the Netherlands. Genetic variation and interrelationships of agronomic characters in landraces of bread wheat from southeastern Iran M. Moghaddam 1 , B. Ehdaie 2 & J.G. Waines 2 1 Department of Agronomy, Tabriz University, Tabriz, Iran; 2 Department of Botany and Plant Sciences, University of California, Riverside, CA 92521-0124, U.S.A.; ( author for correspondence) Received 13 November 1996; accepted 19 March 1997 Key words: Triticum aestivum L., bread wheat, landraces, genetic variation, path-analysis, yield and yield compo- nents, selection, Iran Summary There is renewed interest in wheat landraces as important sources of genetic variation for agronomic characters. Fifty-three pure lines of bread wheat (Triticum aestivum L.) derived from seven landraces collected from southeastern Iran were used to estimate genetic variation and heritability for 13 developmental and quantitative characters. Path-analysis was used to partition the genetic correlations between grain yield and six grain yield-related traits. Mean values of landraces were also compared with three improved cultivars from California and Iran. Genotypic differences among the landraces and among the pure lines collected from the landraces were highly significant for all characters considered. Compared with the modern cultivars, the landrace genotypes were, on average, later in days to heading and taller than the cultivars but had lower values for number of grains per spike, 1000-grain weight, grain yield and harvest index. Some landrace genotypes were similar to the modern cultivars for grain yield. Moderate to high genetic variation was displayed by number of grains per spike, number of spikes per plant, 1000-grain weight, and harvest index. The heritability estimates ranged from 59% for grain yield to 99% for days to anthesis. Expected genetic advance (as% of the mean) was 34% for number of spikes per plant, number of grains per spike, and 1000-grain weight. Days to heading and to anthesis correlated positively with number of spikes per plant, shoot biomass, and straw biomass but negatively with number of grains per spike and harvest index. The strong direct effect of number of spikes per plant on grain yield was completely counterbalanced by its indirect negative effects via number of grains per spike and 1000-grain weight. Number of grains per spike and 1000-grain weight were positively correlated with grain yield, and they had large direct effects. These two characters, however, were negatively correlated and exhibited a substantial counterbalance effect via one another and via number of spikes per plant. The landraces could be improved by intercrossing the promising genotypes identified in this study, with simultaneous selection for earliness, fewer number of spikes per plant, greater number of grains per spike and heavier grains. For further improvement, crossing programs between the landraces and introduced germplasm may be necessary. Introduction Bread wheats (Triticum aestivum L.) and durum wheats (T. turgidum L. ssp. durum Desf.) have been culti- vated in Iran since ancient times, and the country is considered to be part of the center of origin (Vavilov, 1949/1950) and of genetic diversity for these wheats (Harlan, 1971). Bread wheat is the most important crop cultivated in Iran. Landraces are still cultivated in traditional wheat-growing areas. There is renewed interest in wheat landraces and primitive cultivars as important sources of genetic variation (Brush, 1995) mainly because of the trend toward greater uniformity that has narrowed the genetic base of modern wheat cultivars, thus increasing their vulnerability to biotic and abiotic stresses. Harlan (1975) defined a landrace as a mixture of genotypes that evolved, largely by natural selec-