Investigating the effect of corm weight, mycorrhiza fungi and Azotobacter bio fertilizer on qualitative characteristic and secondary metabolites of saffron (Crocus sativus L.)

Abstract

Introduction: Saffron (Crocus sativus L.) is a valuable medicinal plant and a fragrant and expensive export spice from the lily family. Today, the positive results of using biofertilizers have led farmers to use more biological and organic fertilizers in saffron cultivation. In the meantime, the use of biofertilizers is considered due to the increased water retention capacity and nutrient absorption. Also, the combination of low-input ecological systems such as co-inoculation of crops with mycorrhiza fungi and nitrogen-fixing bacteria can be a suitable and environmentally friendly alternative to chemical fertilizers and today's high-input systems. Therefore, the present study was conducted to investigate the effect of corm weight, mycorrhizal fungi, and Azotobacter biofertilizer on qualitative characteristic and secondary metabolites of saffron, so that by selecting the best amount of biofertilizers and the appropriate corm weight of the saffron, and as a result, reducing the use of chemical fertilizers, steps can be taken to develop the cultivation and improve the yield of this important medicinal plant. Materials and Methods: In order to investigate the effect of corm weight, mycorrhizal fungi and Azotobacter biofertilizer on qualitative characteristic and secondary metabolites of saffron, an experiment was conducted in the 2023-2024 crop year as a factorial design in a randomized complete block design at the Birjand Agricultural Faculty Research Farm. The experimental factors included three levels of corm weight (0.1 to 4, 4.1 to 8 and 8.1 to 12 grams), two levels of bacterial biofertilizer (application and non-application of Azotobaror-1 fertilizer containing Pantoea agglomerans strain O4 bacteria) and two levels of mycorrhizal biofertilizer (containing arbuscular mycorrhizal fungi strains Glomus mosseae, Glomus intraradices and Glomus etunicatum and a control without mycorrhiza). Bacterial treatments were applied in the first year of planting by inoculating saffron corms by preparing a suspension of the above bacteria mixed with distilled water in two times. The first time was done before planting by dipping the corms and the second time was done with irrigation 40 days after planting and also in the first irrigation of the second year according to the instructions of Zistfanavar Sabz Company. Mycorrhiza treatments were done at a rate of 10 grams for each seedling by adding it to the planting hole at the time of planting according to the instructions of Daneshbonyan Zist Sepidan Hayat Paya Company. Results and Discussion: The results of the interaction effects of the weight of the corm, mycorrhizal fungi and Azotobacter bacteria on the photosynthetic pigments of saffron leaves showed that The treatment of the corms of the weight group of 8.1-12 grams and the use of mycorrhizal fungi and Azotobacter bacteria increased chlorophyll a and total chlorophyll by 225.92 and 148.57 percent, respectively, compared to the treatment of the corms of the weight group of 4.1-8 grams and no use of fungi and bacteria. The treatment of 8.1-12 grams of corm and the use of mycorrhizal fungi and Azotobacter bacteria increased carbohydrate by 51.08 percent compared to the treatment of the corms of the weight group of 0.1-4 grams and the use of Azotobacter bacteria, and total phenol by 127.07 percent compared to the control treatment. The combined treatment of mycorrhizal fungi and Azotobacter bacteria had the highest amount of flavonoids. The highest content of crocin, safranal and picrocrocin was obtained from the treatment of the corms of the weight group of 8.1 to 12 g and the lack of use of mycorrhizal fungi and the use of Azotobacter bacteria. Conclusion: Simultaneous application of Azotobacter bacteria and inoculation of 8.1-12 g corms with mycorrhizal fungi improved photosynthetic pigments and biochemical properties, and planting 8.1-12 g corms and using Azotobacter bacteria increased the active ingredients of saffron. Therefore, the use of biofertilizers and the development of mycorrhizal hyphae in agricultural soil, including in the planting site of saffron corms, can improve saffron cultivation in sustainable agriculture and reduce losses caused by excessive use of chemical fertilizers.