Biochemical and histological studies were made on roots of pepper (Capsicum
annuum) infected with root-knot nematode and treated by certain chemical
resistance inducers (salicylic acid (SA), indol acetic acid (IAA),ethylene (Eth),
Jasmonic acid (JA), in addition to a biofertilizer named (Halex-2). These resistance
inducers were tested at three concentrations 100, 200 and 300 μM for SA, IAA, and
Eth and 15, 20 and 25 μM for JA while the biofertilizer was tested at 7g/L as biotic
resistance inducers against root-knot nematode Meloidogyne incognita under
greenhouse conditions at the Faculty of Agriculture Shebin El-Kom, Menoufia
University in season 2016. All concentrations of the tested inducers significantly
reduced root-galling and nematode population in soil as well as the number of egg
masses and developmental stages per root system. The greatest inhibition effect on
reproduction of nematode was recorded with Eth at 300μM, which did not
significantly differ from that of a nematicide-treated plants. Also, all treatments
significantly enhanced all vegetative plant growth characters compared with the
infected plants. Biochemical analysis showed a significant increase in the activity of
antioxidant enzymes (peroxidase, polyphenoloxidase and catalase), total and
reducing sugars, and total phenols at the highest concentration of the tested
inducers, especially, Eth compared with the nematode-infested plants. Histological
studies indicated that less giant cells were observed in almost all treatments
compared to the nematode-infected control plants. However, the highest
concentrations of IAA, Eth (300μM) and Halex-2 treatments showed a good
performance, with no giant cells found. Sixty days after nematode inoculation, all
treatments (except SA and Halex-2) showed a poor formation of regular giant cells
divided from cytoplasm and contained less number of nuclei compared to the
infected plants. It seems that the tested inducers could be recommended to control
M. incognita on pepper plants. Thereby, decreases the costs and side effects of
using nematicides.