Growth Response of Saffron Replacement Corms to Storage Conditions of Mother Corms during Summer Dormancy

The storage conditions of saffron mother corms during the summer dormancy period, including natural and pseudo-dormancy stages, can probably affect the vegetative growth and the production of replacement corms (RC), which has not received enough attention in previous scientific studies. This experiment was carried out as a complete randomized block design with seven treatments and three replicates during the 2019 growing season in Qaen, Iran. Experimental treatments were three types of corm storage inside the soil [corm planting on 5th June (A) with natural soil temperature as control, A + summer irrigation on 5th August, and A + mulch application obtained from wheat residues at the rate of 8 ton.ha-1)] and four types of corm storage outside the soil [corm storage at room (ambient temperature) for three months started from 5th June + corm planting on 5th September (B), corm storage in constant temperature (25 oC and relative humidity of ~40 %) in incubator for three months + B, three months corm storage at variable temperature in incubator (one month in 20, 25 and 20 oC) + B and corm storage in room temperature (up to 5th August) and incubator (up to 5th September) + B. The studied traits were the length, number, and weight of leaves, the number and weight of the total RC, the weight of the main RC, the average weight of RCs, and the number and yield of RCs in different weight groups. The results showed that mulch application caused the highest length and number of leaves (35 cm and 9 No per plant, respectively). Incubation of corms at variable temperatures led to a significant increase in the total weight of RC. In contrast,  incubation at constant temperature had most significant effect on the number of RC (2022 corms per m2). The highest and the lowest mean weights of RC were obtained in the mulch application (7.23 g) and incubation at constant temperature (2.22 g), respectively. Plant residue treatment (mulch) decreased the number of small RC (less than 6 g) and increased the number of RC in the weight groups of 9-12 and 12-15 g. Incubation of mother corms at variable temperatures led to an increase in the number and yield of RC weighing more than 15 g. Overall, the treatments of plant residue consumption and storage of mother corms at incubator with variable temperatures, in which 66% and 61% of the RC yield was in groups weighing more than 9 g, respectively, were the best experimental treatments in terms of improving the growth of RC.