Effect of Mother-corm Weight on the Yield, Reproductive Growth, Apocarotenoid Content and Production of Daughter Corms in Saffron Aeroponic Cultivation

Due to the novelty of saffron aeroponic cultivation, many aspects related to this system have not been yet studied. This study was conducted to determine the appropriate maternal-corm weight in saffron aeroponic systems. The experiment was arranged as Completely Randomized Design (CRD) with three replications, including five treatments (corms weighting i) less than 4, ii) 4.1-8, iii) 8.1-12, iv)12.1-16 and v) more than 16g) in the Research Complex of Medicinal Plants, ACECR of Southern Khorasan Province. The number and weight of buds, traits related to reproductive growth, traits concerning the growth of daughter corms and qualitative traits including the content of stigma apocarotenoids (crocin, picrocrocin and safranal) were studied. According to the results, by increasing the weight of corms from less than 4 to more than 16 g, the total number of buds in each corm increased from 2.96 to 11.33 and their weight increased from 130 to 1770 mg, respectively. Besides, the traits related to the economic yield of saffron (weight of stigma, weight of the perianth + stamen, weight of flower, and number of flowers) also increased by increasing the weight of the corms. The lowest yield of stigma per maternal corm with 0.12 mg belonged to corms weighing less than 4 g and the two heaviest corms treatments (16.1-1 and more than 16 g) both with 3.38 mg yielded the highest amount of stigma dry weight. By increasing the weight of maternal corm from less than 4 to 16.1-12 g, the number of flowers in each saffron corm increased from 0.026 to 0.555, respectively. Nevertheless, increasing the weight of maternal corms to more than 16 g did not increase the yield-related traits of saffron. Transplanting the corms in the farm (after flowering in the controlled environment) showed that as the weight of maternal corms increased from 16.1-1 to more than 16 g, the number of produced daughter corms increased (to almost double) from 4.11 to 8.50 per maternal corm. However, the results of the average weight of each daughter corm showed a significant decrease of 37% in maternal corms heavier than 16g compared to those of 12.1-16g. In addition, the amount of saffron apocarotenoids in aeroponic cultivation is not dramatically different from soil culture. In general, due to the fact that in the aeroponic cultivation of saffron, the production of higher economic yield and achieving a suitable number of daughter corms that are also of acceptable weight should be considered at the same time, the use of maternal corms weighing 12.1-16g due to the highest reproductive growth and yield of daughter corms from transplanting, is recommended under controlled conditions of aeroponic system.