Putting root-knot nematode-resistant cultivars to the test.
Peanut root-knot nematode is one of the major pests in peanut production in Florida and throughout the Southeast. Along with crop rotation and nematicide application, use of resistant peanut cultivars is a primary method for managing peanut root-knot nematode.
All current root-knot nematode-resistant peanut cultivars derive resistance from the same parental peanut source. When successfully incorporated into a cultivar, this resistance greatly reduces infection and damage caused by peanut root-knot nematode. In fields with severe peanut root-knot nematode pressure, resistant cultivars consistently increase yield relative to susceptible cultivars with nematicide application.
In recent years, the number of peanut cultivars breeder-
designated as root-knot nematode resistant has increased. The primary goals of these new resistant cultivars have been to increase yield and grade as well introduce other desirable traits, such as resistance to other pathogens. While these cultivars have been tested in the areas they were developed, primarily South Georgia, local testing is always useful. Therefore, small plot trials were conducted to compare these resistant cultivars under severe pressure from peanut root-knot nematode.
What Did The Trials Show?
Trials were conducted at West Florida Research and Education Center in 2023 and 2024, as well as North Florida Research and Education Center-Suwannee Valley in 2024. The resistant cultivars listed in Table 1 were included in the trials. Georgia 23RKN was not included either year, and Georgia 22MPR was only included in 2024. Resistant cultivars were compared to root-knot nematode-susceptible Georgia 06G with in-furrow Velum nematicide at 6.5 fluid ounces or Georgia 06G without a nematicide.
Tif NV-HiO/L, Tif NV-HG, Georgia 14N and Georgia 22MPR were very effective at minimizing root-knot nematode infection during the season and mitigating galling at the end of the season. In contrast, in-furrow Velum nematicide was not effective at mitigating root-knot nematode infection or below-ground symptoms in this study.
Unlike other cultivars marked as resistant, ACI N104 showed a more intermediate level of resistance. It did not reduce mid-season infection relative to the susceptible Georgia 06G but had some efficacy at managing pod galling at the end of season. Mid-season root-knot nematode eggs for NFREC 2024 as well as pod galling and harvest root-knot nematode soil counts for WFREC 2024 values, which are not shown in the charts here, were low and not affected by treatments. This was likely due to very hot and dry conditions before the affected assessments.
Reducing Nematodes For Subsequent Crops
Resistant cultivars — except ACI N104 — also consistently reduced final root-knot nematode soil abundances. In addition to demonstrating management for the current crop, managing final root-knot counts can have carryover benefits for maintaining lower root-knot nematode pressure for subsequent crops. ACI N104 helped manage final root-knot nematode counts at NFREC in 2024 but was not effective at WFREC in 2024. This is consistent with previous comments about ACI N104 having a more intermediate level of resistance than other resistant cultivars.
Yield at WFREC in 2023 was very poor at around 1,500 pounds per acre due to extreme heat and drought late in the year, which devastated the unirrigated field trial. At WFREC in 2024, yield was generally greater for the resistant cultivars than Georgia 06G. Georgia 22MPR did not perform as well as the top-yielding cultivars at WFREC in 2024, likely because the stand was poor at that location. In contrast, at NFREC, Tif NV-HG and Georgia 22MPR yielded better than the other resistant cultivars or Georgia 06G. Tif NV-HG was the most consistent performer for the 2024 trials, which provides some reassurance, as it will be the most widely available root-knot nematode-resistant peanut cultivar this year. Inconsistent yield with other resistant cultivars was unexpected because of prior consistent yields for resistant cultivars under root-knot nematode pressure. The challenging environmental conditions in these trials likely contributed to inconsistency.
For growers wanting to try a resistant cultivar for the first time, or switching to a new resistant cultivar, start on limited acreage. Planting side-by-side with a familiar cultivar can be a good place to start. Additional information about these and other cultivars can also be found on the Florida peanut team website at nfrec.ifas.ufl.edu/florida-peanut-team. PG
