The host status of glyphosate-tolerant soybean genotypes to Meloidogyne incognita and Pratylenchus infection

Akhona Mbatyoti,Antoinette Swart,Mariette Marais,Annelie De Beer,Hendrika Fourie,Dirk De Waele,Mieke Stefanie Daneel

doi:10.1007/s40858-020-00416-y

Abstract

The host status of South African adapted, genetically modified (GM) glyphosate-tolerant soybean genotypes to root-knot (field and glasshouse) and lesion (field) nematodes were assessed. Analyses of root and soil samples of 29 genotypes (collected from seven production areas during the 2014/15 season) enabled the identification of nine plant-parasitic nematode genera and 10 species. Predominant endoparasitic genera in root samples were Meloidogyne (Meloidogyne incognita and M. javanica) and Pratylenchus (Pratylenchus brachyurus, P. zeae and P. teres). Rotylenchulus parvus was the predominant semi-endoparasite in soil, followed by Scutellonema brachyurus and Helicotylenchus sp. Only ‘PAN 1583 R’ and ‘PAN 1521 R’ maintained less than 10% of the Meloidogyne spp. densities present in roots of the most susceptible genotype, while all genotypes were susceptible to the Pratylenchus spp. The host status of 36 soybean genotypes to M. incognita infection, evaluated in two follow-up glasshouse experiments terminated 56 days after inoculation of ca. 1000 M. incognita eggs and second-stage juveniles (J2) per seedling, varied substantially for final population density (Pf), reproduction factor (Rf) and relative percentage susceptibility (%S). Only ‘PRF-GCI7’ and the resistant reference ‘LS 5995’ had Rfs < 1 for both experiments, despite higher minimum and maximum temperatures recorded for the second experiment. Continuous evaluation of soybean genotypes for their host status to predominant nematode pests and their use to reduce densities of such species in producer’s fields are crucial to enable sustainable crop production, and contribute towards food provision and security.

Highlights

Soybean (Glycine max L.) is an important oilseed and protein crop cultivated in South Africa (Dlamini et al 2014; PRF 2020), with genetically modified (GM), glyphosate-tolerant soybean genotypes dominating local production
Meloidogyne incognita was the predominant root-knot nematode species, with high Mean population density (MPD) (252219) and Prominence value (PV) (236680) per 50-g roots when data were pooled across localities and genotypes, compared to substantially lower MPD (69260) and PV (25915) for M. javanica when data of all genotypes were combined per locality
Glasshouse host status evaluations showed that genotypes LS 5995 and PRF-GCI7 consistently showed resistance to M. incognita with reproduction factor (Rf) < 1 and %S < 10, confirming results by Fourie et al (2006) and Venter (2014)

Summary

Introduction

Soybean (Glycine max L.) is an important oilseed and protein crop cultivated in South Africa (Dlamini et al 2014; PRF 2020), with genetically modified (GM), glyphosate-tolerant soybean genotypes dominating local production. Pronounced changes have been experienced in terms of the implementation of advanced technology and cropping practices in soybeanbased cropping systems since the first nematode survey was done in the mid-1990s (Fourie et al 2001) These are for example represented by the commercialization of glyphosatetolerant soybean genotypes (from the 2001/2002 growing season (Wolson 2007) and increased conservation agriculture being practiced by local producers (Engelbrecht 2016). In South Africa, about 57 plant-parasitic nematode species have been listed on soybean (Marais et al 2017a; Mbatyoti et al 2020) with root-knot nematodes (Meloidogyne spp.) being predominant (Fourie et al 2015). Mainly due to Meloidogyne spp. infection, ranging from 25 to 100% have been reported for South African production areas (Riekert and Henshaw 1998; Fourie et al 2015)

Objectives

Methods

Results

Conclusion