Population and molecular genetics of root-knot nematodes

<p>This thesis describes studies of root-knot nematodes <em>Meloidogyne</em> spp. - an economically important pest in agriculture - using population and molecular genetics. Variability in virulence to <em>Mi</em> bearing tomato genotypes is shown for <em>Meloidogyne</em> spp <em>.</em> isolates and their impact of implementation of proper management systems is discussed. Genetic polymorphisms in <em>Meloidogyne</em> spp. were assessed using molecular techniques that reveal nuclear and mitochondrial DNA divergence on different hierarchical levels. cDNA library constructed from the pre-parasitic second stage juveniles of <em>Meloidogyne incognita</em> was screened by single pass 5'-end sequencing <em></em> to investigate genes expressed at the onset of parasitism. One expressed sequence tag homologous to an endoxylanase was used to identify a novel cell wall degrading enzyme - xylanase. Several lines of evidence support the endogenous origin of the nematode xylanase. The amino acid sequence revealed a high similarity with bacterial xylanases indicating that nematode xylanase may have been acquired from bacteria by horizontal gene transfer.</p>