The Effect of Corm Storage Conditions During the Summer Dormancy Stage on Reproductive Growth and Yield of Saffron. (English)

Introduction: Environmental factors, especially temperature, are very important in the proper occurrence of saffron flower initiation stage during summer. In areas affected by heat stress, any factor that reduces the stress intensity seems to be beneficial in improving saffron reproductive growth. Corm storage under desired environmental condition is a potential strategy, when saffron is grown as an annual crop. In perennial saffron plantation, where the corms spend the flowering stage in the soil, other solutions should be considered for the proper occurrence of the flowering stage. One of these solutions is to use plant residues in the field surface to reduce the soil temperature. The presence of plant residues causes shading on the soil surface, increases the amount of sunlight reflection, reduces evaporation from the soil, regulates the moisture content of the soil, and reduces the temperature at the depth of the corm placement. Another possible solution to adjust the soil temperature during the flower initiation phase of the corm is to carry out summer irrigation, but there is not enough certainty about its usefulness. Therefore, the aim of the current experiment was to investigate the effect of storage conditions of corms, as well as the effect of summer irrigation and the application of plant residue mulch on saffron flowering. Materials and Methods: To investigate the effect of corm storage conditions on saffron reproductive growth an experiment was carried out as complete randomized block design with seven treatments and three replicates during 2019 growing season, in Qaen, Iran. Experimental treatments were three types of corm storage inside the soil [corm planting in 5^th June (A) with natural soil temperature as control, A + summer irrigation in 5^th August and A + mulch application obtained from wheat residues at the rate of 8 ton ha^-1)] and three types of corm storage outside the soil [Corm storage at room (ambient temperature) for three months started from 5^th June + corm planting in 5^th September (B), Corm storage in constant temperature (25 °C 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 °C) + B and corm storage in room (up to 5^th August) and incubator (up to 5^th September) + B. Results and Discussion: Results showed that summer irrigation increased the number, length and weight of cataphylls compared to control. Corm storage outside the soil (room or incubator) reduced the weight and length of cataphylls. Control and summer irrigation treatments had no significant different in terms of flower number, flowering rate and flower yield, but were superior to other treatments in terms of all the mentioned traits, especially compared with the room storage treatment. The highest values of mean flower weight (0.37 g), flower length (7.6 cm) and stigma length (2.83 cm) were obtained in mulch application treatment. Mulch application failed to improve flower and stigma yields, despite decreasing the soil temperature during the flower initiation stage. The highest values of stigma yield were gained at control, summer irrigation and mulch application (8.07, 7.28 and 6.40 kg ha^-1, respectively), which were significantly more than those obtained at room storage (3.24 kg ha^-1), storage in incubator with variable temperature (3.68 kg ha^-1), storage in room and incubator (3.89 kg ha^-1) and storage in incubator with constant temperature (4.28 kg ha^-1). Conclusion: Overall, the passage of saffron flower initiation stage inside the soil significantly improved the flowering of the plant compared to the passage of this period outside the soil under room or incubator conditions. Conflict of Interest: The authors declare no potential conflict of interest related to the work. [ABSTRACT FROM AUTHOR]

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