Radopholus duriophilus sp. n. (Nematoda: Pratylenchidae) from Western Highland of Vietnam

Abstract

Abstract A new species of the genus Radopholus associated with durian (Durio zibetinus M.) in the Western Highland of Vietnam is described as Radopholus duriophilus sp. n. The new species is close to R. similis, but is distinguished from R. similis by the position of the excretory pore located posterior to pharyngo-intestine junction (vs at level of pharyngo-intestine junction), oval shape sperm (vs rod-like), four incisures terminating far behind position of phasmid (vs three incisures terminating at or just behind phasmid), and bursa in male never reaching tail terminus (vs bursa reaching tail terminus). Females of R. duriophilus sp. n. differ from R. nativus females by stylet length (16.5-19 vs 19-23 μm), oval or kidney-shaped sperm (vs rod-like), four incisures at level of phasmid (vs three) and their areolated lateral field (vs not areolated). The position of excretory pore of both female and male is located posterior to pharyngo-intestine junction (vs at level or anterior to pharyngo-intestine junction). Females of R. duriophilus sp. n. differ from R. clarus females by stylet length (16.5-19 vs 19-21 μm) and areolated lateral field (vs no areolation). Females of R. duriophilus sp. n. differ from R. musicola females by their lateral field with equidistant incisures at mid-body (vs two deep outer folds and two faint shallow inner incisures), oval or kidney-shaped sperm (vs rod-like), and rounded terminus tail (vs sharply pointed). The species also sp. n. differ in male stylet length (11.5-15 vs 8.8-12 μm). Females of R. duriophilus sp. n. differ from R. bridgei females by stylet length (16.5-19 vs 15-17.5 μm), median bulb length (11-16.5 vs 11-13 μm), length of hyaline tail (3-11 vs not more than 4 μm), and lateral field areolated for entire body (vs not areolated except irregularly on neck and tail). The male differs by stylet length (11.5-15 vs 10-12 μm) and length of the hyaline portion (4-9 vs 1-4 μm). In addition, the relatively high level of ITS sequence divergence of the new species from R. similis populations and the presence of nucleotide autapomorphies support a separate specific status for these durian populations. Results of surveys revealed that R. duriophilus sp. n. is rather widely distributed in durian orchards and associated with decline and death of trees in many durian nursery gardens. Densities of nematode population reached thousands of individuals per g of root samples.