Activity of indolyl-3-acetic acid oxidase and peroxidase in roots of carrot infested with Meloidogyne hapla Chiuu.

Abstract

IAA-oxidase and peroxidase activity was measured in storage and side roots of healthy and M. hapla infested carrots of two sultivars. Cultivar 'Perfekcja' is sensitive whereas cv. 'Slendero' is tolerant to the northern root-knot ne-matode. 3-, 4-, and 5-month-old plants were subjected to analyses. In M. hapla infested plants of both cultivars IAA-oxidase inhibitors accumulated. Kinetics of IAA oxidation in vivo were the same in healthy and infested plants. IAA-oxidase activity in vitro was inhibited in crude extracts of the infested tissues, the inhibition being prevented by PVP. Peroxidase activity increased in secondary phloem and decreased in galled side roots of both cultivars when compared with healthy controls. In galled side roots of the youngest 3-month-old plants peroxidase activity was not decreased. IAA-oxidase inhibitors accumulated in the infested roots.It is concluded that M. hapla has no direct effect on IAA-oxidase. Degree of tolerance to nematodes is correlated with the ratio of IAA-oxidase inhibitors to IAA-oxidase rather than with the absolute activity of IAA-oxidase.