Agro-morphological and genetic diversity of Indian large cardamom cultivars (Amomum subulatum Roxb.) in the sub Himalayan tropics

Large cardamom (Amomum subulatum Roxb.) or black cardamom, indigenous to moist deciduous and evergreen forests of sub-Himalayan tropics, is a highly priced aromatic spice belonging to the family Zingiberaceae. The dried ripe fruit is the spice of commerce and the seeds have similar properties as those of small cardamom (Elettaria cardamomum Maton). It is the most important cash crop of Sikkim state of India, and is cultivated in northeastern states and neighboring nations of Nepal and Bhutan. Though tremendous variability exists among the natural cultivars, genetic diversity has not been explored much and documented. The primary objective of this study was to assess the morphological and genetic diversity among natural cultivars and released cultivars of Amomum subulatum. Six morphologically distinct natural cultivars viz., ‘Ramsey’, ‘Golsey’, ‘Sawney’, ‘Varlangey’, ‘Seremna’, and ‘Ramla’ and 2 released selections ICRI Sikkim 1 and ICRI Sikkim 2 were selected. A total of 23 morphological traits were considered for morphological characterization based on IPGRI descriptor for small cardamom, a close relative, as descriptors are not yet released for this crop. Genetic diversity was evaluated using inter simple sequence repeats (ISSR) and simple sequence repeats (SSR) markers. Cluster analysis was performed using Jaccard’s coefficient, to construct a dendrogram with unweighted pair group method by arithmetic average (UPGMA) matrices. The results based on ISSR markers substantiated the abundant morphological diversity among the natural cultivars. Morphological and molecular marker studies would be a step forward in defining descriptors for large cardamom and for breeding and introgression of new alleles from unutilized germplasm accessions.