Molecular phylogeny and morphological studies reveal a 30-year- old rain tree (Samanea saman) maintains populations of Meloidogyne enterolobii, a new host plant in Thailand

Samanea saman (Jacq.) Merr., commonly known as rain tree, is a crucial shade tree with traditional medicinal properties. In our study, 50 soil samples were collected around the rhizosphere of rain tree in Bangkok, Pathum Thani, Uttaradit, Khon Kaen and Ubon Ratchathani Provinces in Thailand. Meloidogyne populations were only found in soil samples from Mueang district, Khon Kaen Province and a 30-year-old rain tree exhibited root gall symptoms caused by root-knot nematodes (Meloidogyne) on its adventitious roots. The species of the nematodes were identified based on its morphological and molecular characteristics. The results demonstrated that the perineal patterns and morphometrics of the nematodes were highly similar to the original description of M. enterolobii, except for a squarish dorsal arch and two faint lateral lines. During the molecular analysis, nematode DNA was extracted and amplified using three primer sets, C2F3/1108, D2A/D3B and MK7F/MK7R SCAR primer, to generate polymerase chain reaction (PCR) products of 700, 750 and 520 bp, respectively. The polygenetic tree of the two markers displayed similarity among the COII and the 16S rRNA gene in mitochondria and the D2/D3 region in 28S rRNA. Therefore, the nematodes were identified as M. enterolobii Yang and Eisenback, 1983. This study reports a new host record of M. enterolobii on rain tree.