Induction of resistance in pepper plants against powdery mildew disease by using chemical and biological inducers

Abstract

The present study was carried out to evaluate the efficacy of some chemical and biotic inducers of resistance in controlling powdery mildew of pepper plants. The chemical inducers namely, mono-potassium phosphate (KHPO24), di-potassium phosphate (KHPO) and potassium silicate (KSiO2423) were applied as foliar treatment. The biotic namely, Bacillus subtilis as (Rhizo-N®), Trichoderma harzianum as (Plant Guard®), Pseudomonas fluorescens (two isolates Pf1, Pf2), one isolate of Trichoderma harzianum (T1), and Trichoderma viride (T2) were applied as seed and soil treatment. Combined treatment of chemical and biotic inducers was also tested. The efficacy of treatments was expressed of reduction in disease severity and conidial production on leaf tissue. The highest significant reduction in disease severity were recorded when KSiO23 (17 mM), KHPO (100 mM) and KHPO2424 (100 mM) were applied as foliar spray, the caused reduction in disease severity reached 59.0, 54.6 and 50.0 % respectively. As for the biotic inducers results showed that Rhizo-N® (Bacillus subtilis), Plant Guard® (Trichoderma harzianum) and Pseudomonas fluorescens (Pf1) significantly decreased powdery mildew severity compared with untreated control, reduction in disease severity recorded 46.8 %, 44.7 % and 43.5 %, respectively. Results clearly showed that the application of chemical inducers as foliar spray combined with biological inducers as seed or soil treatment showed more significant reduction in disease severity of powdery mildew than chemical and biological inducers alone. All chemical and biological inducers improved plant growth, fresh weight, dry weight, plant height and leaf area (cm2) and reduced the defoliation as compared with untreated control. Biochemical studies showed that the combined biotic and chemical treatments increased enzyme activities such as peroxidase and polyphenol oxidase as well as phenols and pigments.