Genetic structure and diversity of ajowan (Trachyspermum ammi) populations based on molecular, morphological markers, and volatile oil content

Abstract

ISSR and morphological markers were used to assess the genetic variation in 117 ajowan accessions belonging to 25 populations collected from different geographical regions in Iran. For this purpose, fifteen primer combinations were applied to produce 120 polymorphic bands. The dendrogram delineated ajowan accessions into three major groups based on STRUCTURE software analysis. Principal coordinate analysis (PCoA) confirmed the results of cluster analysis but morphological classification showed no significant relationships with molecular results. Among the populations, Farsfars and Yazmol exhibited a relatively high genetic distance (0.54) but they possessed relatively low (255.16gr/m2) and high (435.9gr/m2) seed yields, respectively. Esfahfo and Yazsad populations exhibited a relatively high genetic distance (0.64) as well as high essential oil content (5.37% and 4.73%, respectively). While only about 30.33% of the total genetic variation was detected among the populations, 64.65% of the total variation was observed within the populations. The populations investigated showed a high genetic differentiation (Gst=0.35) and a low gene flow (Nm=1.85). From among the populations, the Eastern and Western ones accounted for the highest values of percentage of polymorphic loci PPL (%), Shanon index (I), and heterozygosity. The results of population structure analysis revealed high admixture of ajowan accessions in the populations. Finally, The results of the present study may contribute to a better understanding and management of conservation and breeding of the ajowan germplasm.