Author(s):

Vijay Kumar and Sunita Chandel

Abstract: To study the mechanism of resistance developed in rose cultivar High and Peace against Podosphaera pannosa was pretreated with SAR chemicals viz. salicylic acid, β-aminobutyric acid, calcium silicate, potassium bicarbonate, phosphoric acid, dipotassium orthophosphate and potassium silicate were assayed at six sampling intervals of 0 (at time of spray), 2, 4, 6 days, at bud formation and one month after bud formation for various biochemical constitutions like reducing and non-reducing sugars, total phenols, peroxidase and polyphenol oxidase activity and PAL activity. The results revealed that the dipotassium orthophosphate treated rose leaves developed highest amount of the reducing sugar (146.33 µg/g) with passage of time which was followed by salicylic acid (133.72 µg/g), β-aminobutyric acid (128.50 µg/g) and potassium silicate (124.00µg/g). While the lowest amount of reducing sugar was recorded in calcium silicate (117.67 µg/g) including control (115.33 µg/g). However, dipotassium orthophosphate treated rose leaves contain highest amount of the non-reducing sugar (65.00 µg/g) followed by salicylic acid (52.00 µg/g), β-aminobutyric acid (49.33 µg/g), potassium silicate (41.00 µg/g) and potassium bicarbonate (37.00 µg/g) while least amount of non-reducing sugar was found in calcium silicate (31 µg/g) treated plants followed by phosphoric acid (35.00 µg/g) at 6th day of spray. The total phenol (137.67 µg/g) was higher in dipotassium orthophosphate and salicylic acid with 130.72 µg/g irrespective of sampling intervals and different plant stages in comparison to rest of the treatments. maximum polyphenol activity in dipotassium orthophosphate treated rose leaves (0.261) followed by salicylic acid (0.242), β-aminobutyric acid (0.218) and potassium silicate (0.196) while lowest in calcium silicate (0.112) followed by phosphoric acid (0.145) and potassium bicarbonate (0.175). revealed the effectiveness of dipotassium orthophosphate in enhancing the peroxidase activity being highest (0.416) followed by salicylic acid (0.390), β-aminobutyric acid (0.360), potassium silicate (0.343) and potassium bicarbonate (0.313). While the least activity registered in calcium silicate (0.225). The highest PAL activity registered in dipotassium orthophosphate (0.586) followed by salicylic acid (0.523), β-aminobutyric acid (0.480) and potassium silicate (0.438) and potassium bicarbonate (0.403). While least PAL activity was observed in treatment with calcium silicate (0.287).

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