Induced resistance in pepper plants against root knot nematode by some inducers in relation to the histological changes

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.