Evaluation of growth and yield of indigo ecotypes in different sowing dates and genetic diversity analysis using AFLP markers

Indigo (Indigoferatinctoria L.), as a forgotten crop, has immense industrial and medicinal value. In this research, the effect of sowing date on the leaf, seed, and dye yield of indigo was examined at Jiroft, Iran, during the 2013 and 2014 growing seasons. The experiment was arranged as a split-plot based on a randomized complete block design with three replications. Planting dates (5 May, 20 May, and 5 June) and indigo ecotypes as landraces of Jiroft, Roudbar, Rigan, and Ghale-ganj were considered as main and subplots, respectively, aiming to evaluate their effects on pod number/plant, 1,000-seed weight, seed number/pod, leaf dry weight, seed yield, as well as indigo dye percentage and yield. The results indicated that the indigo content was greater at the second sowing date (0.68%) than the first (0.66%) and third (0.65%) dates. Further, the indigo percentage was greater in Jiroft and Roudbar ecotypes compared with Rigan and Ghale-ganj. Seed yield at the second and third sowing dates significantly increased (560.3 kg ha(-1)) and reduced (188.4 kg ha(-1)), respectively, compared with the first sowing date (261.4 kg ha(-1)). Furthermore, the highest value of leaf dry weight, indigo yield, and seed yield were obtained from the Jiroft ecotype at the second sowing date; in contrast, the lowest of these parameters were recorded in the Ghale-ganj ecotype at the latest sowing date. Moreover, the genetic diversity of ecotypes was studied using the amplified fragment length polymorphism (AFLP) marker. Based on the dendrogram, the four ecotypes of indigo were divided into three groups; thus, Jiroft and Rudbar, geographically close to each other and almost the same, were in one group, and Reagan and Ghale-Ganj were in separate groups. Overall, based on this research results, Jiroft and 20 May could be suggested as the best ecotype and sowing date of indigo for the examined region. Obtained results can also be useful for expanding and facilitating the cultivation of neglected plants.