Histopathological changes and enzymatic activities induced by Meloïdogyne Incognita on resistant and susceptible potato

International audienceAll potato cultivars are susceptible to root-knot nematodes (Meloidogyne spp.) which infest the roots and induce galls on the surface and necrotic spots in the flesh tuber of potato, Solanum tuberosum. Infested tubers are unacceptable for processing and fresh market. Tubers are also putative source of dissemination of the nematode. A French nematode- resistant tetraploid potato genotype gained from ex-S. sparsipilum material hybridized with S. tuberosum in F1 and in their back cross progenies and designated as 02T.155.6 was tested and compared in the present study in Egypt as a suitable different environment. Histopathological changes and chitinase activity induced by M. incognita population, of common occurrence in Egypt, in four French tetraploid materials and two common cultivars known as nematode- resistant and susceptible potato genotypes were investigated. Hypertrophied cells were initiated in both cortical and steler regions of the roots which were then developed to abnormal xylem elements expanding into the cortex in French susceptible genotypes designated as 02T.149.6, 02T.150.54, and 02T.157.16. Nematode within the vascular tissue (stele) could induce giant cell development close to nematode heads. The largest number of such induced cells was shown by the cultivars Spunta and Diamant. The clone 02T.155.6 with putative nematode resistance demonstrated none or very little nematode development. Recently dead second stage juveniles could also indicate incompatible plant reaction to the invading nematodes in 02T.155.6. M. incognita, Giza population, resistance was generally more coherent to 02T.155.6 as demonstrated by our histological investigations but less coherent as shown by another Egyptian M. incognita population. Chitinase activity was enhanced in M. incognita (Giza)-inoculated with respect to uninoculated roots in all plants. After inoculation, such an activity generally increased more in roots of a potato genotype previously known to have resistance or relatively low numbers of both nematode galls and eggmasses than in the other tested cultivars. Peroxidase and catalase activities of nematode- inoculated with respect to uninoculated potato roots were presented and discussed