Molecular and Morphological Characterization of an Unusual Meloidogyne arenaria Population from Traveler's Tree, Ravenala madagascariensis.

An unusual variant of Meloidogyne arenaria was discovered on roots of a traveler's tree (Ravenala madagascariensis) intended for display at a public arboretum in Pennsylvania. The population aroused curiosity by the lack of visible galling on the roots of the infected plant, and the female vulval region was typically surrounded by egg sacs. Most morphometrics of the population fit within the ranges reported for M. arenaria, with a mosaic of features in common with either M. platani or other tropical Meloidogyne spp. Molecular characterization included analysis of four loci. The mitochondrial sequence, extending from cytochrome oxidase II (COII) to the 16S (1RNA) gene, was nearly identical to another M. arenaria population and closely related to sequences from M. morocciensis and M. thailandica. The 28S D2-D3 expansion segment was most similar to those from M. arenaria, M. incognita and M. paranaensis, and the IGS-2 was most related to those from M. thailandica, M. arenaria and M. incognita. Analysis of partial Hsp90 genomic sequences revealed the greatest similarity to M. arenaria, M. thailandica and an Hsp90 haplotype from M. floridensis, and a composite sequence comprised of EST from M. arenaria. No morphological or molecular features clearly distinguished this population as a new species, and, when considered as a whole, the evidence points to its identification as M. arenaria.