Comparative Effectiveness of Potential Elicitors of Soybean Plant Resistance Against Spodoptera Littoralis and Their Effects on Secondary Metabolites and Antioxidant Defense System

Abstract

Cotton leaf worm (Spodoptera littoralis) is considered one of the most destructive agricultural pests in Egypt. It is overcome by the producer by using chemical pesticides, but that leads to the appearance of new generations and causes environmental pollution. So in the present investigation six soybean genotypes (Giza-82, Giza 22, Giza 83, Giza 21, Giza 35 and Giza 111) were planted under natural infection with cotton leaf worm. The effect of two elicitors, methyl jasmonate (20 µM MeJA) and sodium nitroprusside (500 µM SNP) on the six soybean genotypes was studied to enhance the ability of the susceptible genotypes to resist cotton leaf worm. Results showed that Giza 35 and Giza 111 showed tolerance performance under natural infection compared to Giza 22 and Giza 82 as sensitive ones, while Giza 83 and Giza 21 showed moderate tolerance. Treatments with MeJA and SNP positively affected contents of secondary metabolites (phenol, flavonoid and tannin), non-enzymatic antioxidants (anthocyanin, tocopherol and ascorbic acid) and enzymatic antioxidants (catalase, peroxidase, polyphenol oxidase and Guaiacol peroxidase) in shoots of all soybean genotypes. Treatment with MeJA was found to be more effective than SNP and enhanced the resistance of the susceptible genotypes. In conclusion, treatment of soybean plants with MeJA and SNP would be effective enhancing the ability of these plants to resists cotton leaf worm infection and increased secondary metabolites and antioxidants responsible for plant defense.