Saffron Agronomy and Technology

Abstract The saffron bulb mite (Rhizoglyphus robini Claparède) is considered a serious threat in saffron cultivation areas in Iran. This soil-borne mite reduces the growth and is a cause of the yellowness of saffron plants and eventually destroys the corms. Due to the significance of this strategic product and its medicinal and export aspects, it is impossible to register any synthetic chemical compounds against pests and diseases of this plant in the country. Therefore, finding non-chemical and based on natural substances methods for the control of this pest is necessary. In this research the use of mite-pathogenic fungi is considered a promising approach for controlling this pest. To isolate and identify these fungi, soil samples were collected from saffron farms in 32 regions of Torbat-Heydarieh County in Khorasan Razavi province in 2022 and 2023. Overall, 55 fungal isolates related to eight genera were obtained and among them, 26 isolates could colonize the mites. The potent isolates that killed mites and caused at least 50 percent mortality after ten days were compared statistically. The results showed that on the 10th day, the effect of Metarhizium sp. isolate M-Kh and Cordyceps sp. isolate Co-TZ on mite mortality was 100 percent which was higher than other fungi, but, their difference with some isolates belonged to Beauveria sp. was insignificant (P<0.05). The mite colonization percentage of M-Kh isolate was 100 percent and significantly higher than other fungi (P<0.05). Cladosporium sp., Aspergillus spp., Penicillium spp., Fusarium spp., and Mucor spp. also caused the death of mites, but their effect was insignificant. Based on available information, this is the first report of the pathogenicity of the mentioned fungal genes against the saffron bulb mite in Iran. According to the results, these selected fungi can be used as biological control agents to protect saffron corms against mites.