Phenetic and genetic diversity in Indian Luffa (Cucurbitaceae) inferred from morphometric, ISSR and DAMD markers

Genetic variations and relationships among cultivated and wild genotypes of five taxa of Indian Luffa were examined using inter simple sequence repeats (ISSR), directed amplification of minisatellite DNA (DAMD) markers and morphological characterization. Morphometric evaluation of 21 discrete characters in 51 representative accessions segregated the five taxa of Luffa in three main clusters: the two wild species (L. echinata, L. graveolens) in the first, and the cultivated L. aegyptiaca (smooth gourd) and L. acutangula (ridged gourd)/L. hermaphrodita (Hermaphrodite luffa) in the second and third clusters, respectively. Cumulative data analysis of 15 ISSR and seven DAMD markers revealed high percentage polymorphism (97.67 %), moderate genetic distance (0.06–0.72, avg. 0.51), and low heterozygosity and Shannon index values (H = 0.15; I = 0.22) across all the 76 genotypes assayed. A UPGMA dendrogram, based on the combined marker data, resolved the five taxa in two main clusters with high bootstrap support. The morphological and molecular trees showed incongruence in the number of main clusters resolved and in the disposition of the wild and cultivated taxa in different sub-clusters. The cluster analyses and PCoA plots revealed a nested grouping of the hermaphrodite luffa within the ridge gourd group. The Bayesian STRUCTURE analysis identified three genetic clusters for the five assumed taxa. Outcrossing test revealed a mixed mating system in Indian Luffa. This is the first ever report on the mating system in Luffa using molecular markers. The study also demonstrates the utility of using more than one DNA marker in the assessment of molecular diversity in a widely cultivated crop genus like Luffa with a narrow genetic base.