Pathogenicity and reproduction of isolates of reniform nematode, Rotylenchulus reniformis, from Louisiana on soybean

Authors: KULARATHNA, MANJULA - Louisiana State University; OVERSTREET, CHARLES - Louisiana State University; MCGAWLEY, EDWARD - Louisiana State University; Stetina, Salliana - Sally; KHANAL, CHURAMANI - Louisiana State University; GODOY, FELIPE M. - Louisiana State University; MCINNES, BENJAMIN - Louisiana State University

Submitted to: Nematropica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/22/2019
Publication Date: 9/1/2019
Citation: Kularathna, M.T., Overstreet, C., Mcgawley, E.C., Stetina, S.R., Khanal, C., Godoy, F.C., Mcinnes, B.K. 2019. Pathogenicity and reproduction of isolates of reniform nematode, Rotylenchulus reniformis, from Louisiana on soybean. Nematropica. 49:31-41.

Interpretive Summary: The reniform nematode is a microscopic worm that feeds on plant roots and causes significant yield loss in soybean in the southern United States. Little is known about variability among populations of this nematode in Louisiana with respect to its ability to infect, reproduce, and cause damage to the soybean crop. In greenhouse and microplot trials comparing populations from four parishes in Louisiana (West Carroll, Rapides, Morehouse, and Tensas) on soybean lines resistant or susceptible to the nematode, variation was documented. Across all soybean lines, the Morehouse population caused the most damage to the plants, though reproduction by this isolate was lower than that of the other three populations tested. Though the nematode was able to reproduce on all of the commercial soybean cultivars tested, REV 56R63 supported less reproduction than the others. The variability documented in these populations underscores the importance of using a range of reniform nematode populations by plant breeders aiming to develop soybean varieties with resistance to this pest.

Technical Abstract: The reniform nematode (Rotylenchulus reniformis) is one of the major pests on both soybean and cotton in the southern United States. Although there are resistant soybean cultivars available, this resistance may not be uniform across different geographical isolates of the pathogen. Experiments were conducted to evaluate soybean responses to indigenous isolates of reniform nematode in Louisiana on commercial cultivars and resistant germplasm lines. Experiments in greenhouse and microplot environments were conducted during 2016 and 2017 to evaluate the comparative reproduction and pathogenicity of single populations of R. reniformis isolated from West Carroll (WC), Rapides (RAP), Tensas (TEN) and Morehouse (MOR) parishes of Louisiana. Data from full-season microplot studies, averaged over 2 trials, showed significant differences in reproduction and pathogenicity of the nematode on REV 56R63, Pioneer P54T94R, and Dyna-Gro 39RY57 soybean cultivars. Reproduction by the MOR isolate was 46.8% lower than that by the WC isolate. However, the MOR isolate was the most pathogenic one with 20.8% lower plant and 44.6% lower pod weight compared to the non-inoculated control. Data from 60-day duration greenhouse experiments reflected a similar trend. In greenhouse trials the susceptible cultivar Progeny P4930LL and the resistant PI lines 90763 and 548316 were included with the cultivars employed in the microplots. Reproduction by the MOR isolate was 33% less than that by WC isolate. Reduced reproduction by the MOR isolate relative to the WC isolate was accounted for by a 50% reduction in the numbers of eggs per root system. In both microplot and greenhouse environments, REV 56R63 was a significantly less suitable host than was Pioneer P54T94R, Dyna-Gro 39RY57 and PI 548316.