Tomato plants infected with the root-knot nematode (RKN) M. javanica produce ethylene at a rate several fold higher than the uninfected plants (1). This increase coincides with an increase in 1-amino cyclopropane-l-carboxylic acid (ACC) level in the plant’s root and leaves (2). When excised roots were treated with aminoetoxyvinylglicine (AVG) or aminooxyacetic acid the nematode-induced ethylene production was inhibited, indicating that the nematode-infection induced ethylene production by accelerating the rate of ACC formation from S-adenosyl-methionine. Altering the rate of ethylene production in the infected roots did not affect nematode development up to the 3rd stage of juveniles, nor did it affect nematode penetration and initiation of gall formation. However, development of adult nematodes was markedly inhibited by both ethylene stimulators or inhibitors, whereas the rate of gall growth was accelerated by stimulators of ethylene production and suppressed when the production or action of the hormone was inhibited. Examination of fractured galls with SEM revealed that the hypertrophied cortical parenchyma of the galls treated with AVG, was less developed than the untreated control. On the other hand, the parenchyma of galls treated with supraoptimal concentration of auxin was larger in diameter than that of the untreated galls, due to the induction of ethylene production by the auxine. In all treatments the vascular cylinder was not affected in size and structure, nor were the coencytes induced by the RKN M. javanica.

Part of the Advances in Agricultural Biotechnology book series (AABI, volume 9)