Parasitism of the root-knot nematode Meloidogyne hapla on peony in northern Italy

Abstract

A root-knot nematode was frequently detected on the roots of peony (Paeonia lactiflora Pall.) in northern Italy, inducing typical spherical galls with large egg masses (each averaging 320-350 eggs). According to its typical cuticular perineal pattern, esterase and malate dehydrogenase phenotypes, and morphological observations on adults and juveniles, the nematode was identified as Meloidogyne hapla. Galls induced by the nematode on the roots of peony were variable in size but relatively small (only two to three times the healthy root diameter), located mostly along the root axis and less frequently at the root tips. Numerous lateral roots arising from galled main roots were also galled. Comparative histopathological observations of healthy and M. hapla-infected roots of peony showed cellular alterations induced by the nematode in the cortex, pericycle and vascular parenchyma. Permanent feeding sites of the nematode within root tissues consisted of 3-8 giant polynucleate cells surrounding the lip region of females.