DYNAMICS OF PHENOLS AND DIPHENOLOXIDASE CONTENTS OF COTTON CVS DURING HYPERSENSITIVE AND SUSCEPTIBLE REACTION INDUCED BY XANTHOMONAS CAMPESTRlS PV. MALVACEARUM
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Authors
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S. G. BORKAR* AND J. P. VERMA
Diuision of Mycology and Plant Pathology
Indian Agricultural Research Institute, New Delhi 110 012
Keywords:
Cotton, Intercellular fluid, Phenol, Diphenoloxidase, X.c pv. maluacearum, Susceptible reaction, Hypersensitive reactionAbstract
Leaves of resistant cotton cv. 101-1028 to bacterial blight pathogen Xanthomonas campestris pv. malvacearum (Xcm) contained 69 per cent more total phenol than the leaves of susceptible cotton cv Acala-44. Diphenoloxidase and its activity were more in the leaves of resistant cv than in the leaves of susceptible cv. DPO of cotton cvs was specific to pyrogallol and DOPA in-vitro, but only to pyrogallol in-vivo. DPO of resistant cv was more active (produced more amount of dopachrome in-vitro) with pyrogallol than that of susceptible cv and the formation of dopachrome was dependent on the consumption of molecular oxygen in-vitro and in-vivo. Diphenoloxidase activity in the intercellular fluid of both resistant and susceptible cv was generally the same. However, after inoculation with Xcm, the initial enhancement in DPO activity was more in the intercellular fluid of resistant cv than susceptible cv. Infiltration of Xcm into the leaf tissue decreased the total phenol level in susceptible cv during water soaking reaction by 5.4 per cent, whereas increased them by 2.8 per cent in the leaves of resistant cv during hypersensitive reaction. Presence of higher phenol content and increased DPO activity in the IF (after Xcm inoculation) of resistant cv produced more quickly (than in susceptible cv) the dopachrome responsible for tissue necrosislhyper sensitive reaction; whereas, in the leaves of susceptible cv, low phenol content and slower activity of DPO produced brown pigment or dopachrome more slowly. and allowed the Xcm to multiply rapidly to produce susceptible water soaking reaction.
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