Biochemical and histological changes in sesame roots associated with charcoal rot disease resistance and enhancing plant growth induced by gamma-irradiated seeds at low doses

Abstract

The current study aimed at irradiating sesame seeds with gamma radiation at 4.22, 8.45, 12.68, and 16.9 Gy and 2 and 4 cm to control charcoal rot disease caused by Macrophomina phaseolina (Mp) and also investigating their effects on some biochemical and histological changes in sesame roots associated with charcoal rot disease resistance with enhancing plant growth, seed yield, and oil content. In pot and field experiments under either artificial or natural soil infestation with the Mp inoculum, sowing of irradiated sesame seeds with gamma radiation at low doses significantly reduced the incidence of charcoal rot disease recorded based on root colonization by the Mp fungus and developed symptoms and enhanced plant growth measured by increasing plant height, number of capsules, and seed yield per plant, as well as percent of seed oil content compared with the control of non-irradiated seeds. The irradiation dose of 12.68 Gy was the most effective, followed by the 8.45 Gy dose. The biochemical study of sesame roots associated with charcoal rot disease resistance induced by gamma-irradiating seeds at 12.68 Gy at 2 cm showed a gradual increase in the total protein content, the activity of peroxidase and polyphenol oxidase, phenolic, and lignin contents in plant roots for up to 28 days compared to those originated from non-irradiated seeds. The histological study of the protected plant roots at 28 days old originating from seeds exposed to a 12.68 Gy dose showed a high thickening of the cuticle and epidermis cell walls and lignified cortical cells.