Comparing annual and biennial crop cycle on the growth, yield and quality of saffron using three corm dimensions

Saffron (Crocus sativus L.) is a geophyte plant belonging to the Iridaceae family and it is appreciated for its red dried stigmas used as cooking spice and flavouring agent. Effects of crop cycle length and mother corm dimension, as well as their interaction, have been evaluated on the flowering (morphological traits of flowers, days to flowering, flowering interval and flower production), quantitative traits (stigma and daughter corm yield), vegetative development (leaf and daughter corm traits) and qualitative characteristics (coloring, bittering and aromatic powers) of spice. A two-year field study (2017-2019) was conducted to compare annual and biennial crop cycle of saffron using three corm dimensional classes (D1: 2.0-2.5 cm, D2: 2.6-3.5 cm and D3: 3.6-4.5 cm) according a split-plot design with 3 replications. The results showed that the corms of D3 class, planted in annual crop cycle, produced flowers with the highest stigma length (42.2 mm), and dry weight of stigmas (7.4 mg), stamens (11.4 mg) and tepals (40.7 mg). The highest number of flowers per m2 (311.8) and stigma yield (20.7 kg ha-1) were found when corms belonging to D2 class were planted in biennial crop cycle, meanwhile the highest daughter corms production (35.9 t ha-1) was obtained when corms belonged to D3 class were planted in annual crop cycle. Number of daughter corms per m2 with a horizontal diameter from 3.1 to 4.5 cm and weight from 10.1 to > 25 g decreased as increasing the crop cycle length. In biennial crop cycle, corms of D1 class produced more daughter corms belonged to 3.1-3.5 cm diameter class and to 15.1-20 g weight class compared to D2 and D3 classes. Regarding to the spice quality, coloring and bittering powers were positively influenced by biennial crop cycle. According to International Standardization Organization (ISO 3632) references, the maximum values of color (306.3 A1cm1% 440 nm) and taste (116.2 A1cm1% 257 nm) were reached in spice obtained from "biennial crop cycle x D2 class" interaction. No significant effect of all experimental factors on aromatic power was found. It was concluded that the evaluation of combination between crop cycle length and corm dimension is necessary in the saffron management in order to achieve the optimum yield of stigmas and corms, to improve the qualitative traits of spice and to enhance the by-products as corms of D1 class.