EFFECT OF ABIOTIC AND BIOTIC TREATMENTS ON BACTERIAL ANGULAR LEAF SPOT AND PHENOLIC COMPOUNDS OF CUCUMBER
2007
S Mahmoud
Bacterial angular leaf spot disease caused by Pseudomonas syringae pv. lachrymans is one of the most important foliage disease of cucumber. The present work was planned to control the dis-ease using six inducers i.e. salicylic acid, cobalt sulphate, di-basic potassium phosphate, lithium chloride, potassium silicate and tri-potassium phosphate, in addition two bioagents named Pseu-domonas fluorescens and Bacillus subtilis were applied as foliar treatments to induce systemic resistance in cucumber plants against bacterial angular leaf spot disease. The most effective in-ducers were salicylic acid, dibasic potassium phosphate and lithium chloride, respectively. On the other hand, Bacillus subtilis was least effective one followed by potassium silicate and Ps. fluo-rescens, respectively. While, tri-potassium phos-phate, cobalt sulphate were moderate in this re-spect. Efficacy of used inducers prolonged about till six weeks after treatment.The inducers were shown to increase phenolic compounds of cucumber leaves, whereas after two weeks of treatment up to six weeks, free and total phenol in the treated plants showed higher amounts than those in the untreated ones. Another trend was obtained with conjugated phenol. A positive correlation had been noticed between ef-ficacy of inducers and accumulated amounts of free and total phenol in cucumber leaves, i.e. the higher inducer efficacy the higher free and total phenol accumulation.
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