The southern root-knot nematode (Meloidogyne incognita) is the most important yield-limiting plant-pathogenic nematode that affects soybean production in the mid-South. It is found in nearly all soybean producing counties in Arkansas and can cause significant (>70%) yield loss when the wrong soybean variety (i.e. susceptible) is planted in a field with a high population density of root-knot nematodes.
During the 2018 season, the Lonoke Extension Plant Pathology Program selected 58 soybean varieties that were grouped based on herbicide technologies and maturity groups to be evaluated in a southern root-knot nematode infested field. Due to the number of Roundup and Xtend MG IV entries, this group was divided into two experiments to minimize variability in root-gall ratings.
The final nematode population densities (Pf) collected at harvest ranged from 206-887 individuals per 100 cm3 soil in each test. The Pf counts are lower than in 2017 because most of plants matured early; thus, the peak nematode population occurred before samples were collected at harvest.
Percent of root system galled was estimated for at least 8 root systems from each replication per test at R4-R5 growth stage. Soybean varieties in each category with the lowest gall rating contributed to the greatest yield (Table 1-5).
Soybean varieties with <10% of root of system galled are considered resistant compared to those with the greatest galling percentage. For example, ‘Terral REV 48A46’ is resistant compared to ‘Progeny P 4255 RX’ (2.9/99 = 2.9%).
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On average, the grain yield for these varieties were lower than that from 2017 due to dry summer conditions that favored nematode impact on yield. This information and that on the variety testing website can be used to make decisions about variety selection for the 2019 cropping season.
Download the variety information tables here: 2018 Selected Soybean Variety Performance in RKN Infested Field