Evaluation of rust disease tolerance and antioxidant enzyme activity from organogenesis and somatic embryogenesis in safflower (Carthamus tinctorius L.) cv. NARI-H-15

Abstract

Importance of the work: Rust fungi (Puccinia carthami) play a critical role as major threats to diminishing safflower growth, quality, and productivity worldwide. Therefore, there is a need to develop and deploy rust-resistant safflower plants. Recently, in vitro selection of fungal toxins has been an effective tool for disease resistance in many crops.
Objectives: The present study aimed to standardize an efficient protocol for rust-resistant safflower (Carthamus tinctorius L.) cv. NARI-H-15 plant development through organogenesis and embryogenesis processes using P. carthami fungal culture filtrates (FCFs) as selection pressure.
Materials & Methods: In vitro FCF selection technique with organogenesis and somatic embryogenesis pathways were used for the experimental purpose to develop tolerant plants. Antioxidant enzyme and pathogenicity assay methods were applied to determine the level of tolerance against biotic stress.
Results: For organogenesis, immature leaf calli cultured on 40% FCF-selected Murashige and Skoog (MS) medium induced 22.8% more shoot organogenesis and 16.6% more rooting than cotyledonary leaf calli. For somatic embryogenesis, cotyledon-derived embryogenic calli cultured on 40% FCF-selected MS medium produced 30% more somatic embryogenesis with 17% more germination than immature-leaf-derived embryogenic calli. Fully regenerated FCF-tolerant plants were transferred to pots containing a soil mixture, with 52% of plants survived under greenhouse conditions. Further experiments evaluated the reactive oxygen species scavenging enzymes in FCF-tolerant plants. Catalase activity decreased while peroxidase and superoxide dismutase activities were higher in the FCF-tolerant plants than for the control, based on quantitative and qualitative analysis. The pathogenicity results confirmed the disease resistance of the in vitrodeveloped FCF-treated plants.
Main finding: Application of 40% FCF in tissue culture medium appears to be the reliable strategy for enhancing rust disease resistance in safflower cv. NARI-H-15 against P. carthami.