First Report of Plant-Parasitic Nematodes on Seashore Paspalum (Paspalum vaginatum) in Florida

18S rRNA and COI haplotype diversity of Trichodorus obtusus from turfgrass in South Carolina

The stubby-root nematode, Trichodorus obtusus, was recently identified on zoysiagrass in South Carolina, USA. In Florida, T. obtusus causes more damage than other stubby-root nematodes encountered in turfgrass. The objective of this study was to use morphological analysis, mitochondrial DNA (COI: cytochrome oxidase 1) and nuclear (18S rRNA) sequence data to study the genetic structure and haplotype diversity of populations recovered from turfgrasses in South Carolina. Numerous morphological differences were observed among populations. Three 18S haplotypes were shared among South Carolina and Florida populations, and six mitochondrial haplotypes were identified in South Carolina samples. Of the six COI haplotypes, four haplotypes were restricted to one population from St Augustinegrass. The lowest haplotype diversity was found in samples from zoysiagrass. Sequences of the COI mtDNA gene of T. obtusus were published in GenBank and represent the first mtDNA sequences for the genus Trichodorus.

Effects of Trichodorus obtusus on zoysiagrass and bermudagrass root weight and turfgrass quality

Trichodorus obtusus is a damaging stubby-root nematode encountered on turf. Few reports exist about the effects of T. obtusus feeding on turfgrass in field settings. A 2-year field trial was conducted to evaluate the effects of T. obtusus on turf quality and root weight of Tifway bermudagrass and Empire zoysiagrass. Core samples and turf quality ratings were taken on multiple sampling dates, from plots at multiple locations in South Carolina, USA. Nematode population densities, root weights and turf quality were used to describe the linear and non-linear relationships between them. Zoysiagrass root weights increased, but turf quality decreased with nematode population density. Bermudagrass root weights and quality decreased in response to increased nematode population densities. Our results show that T. obtusus can cause significant reductions in turfgrass quality, and zoysiagrass and bermudagrass were able to tolerate low nematode population densities before turf quality reductions were detectable.