How Well Do Root-Knot Nematode Resistant Peanut Cultivars Perform in Florida?

by | Feb 14, 2025 | Field Crops, Nematodes, Peanut, Pest Management

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. (For more information on nematode management in peanut production, use the following publication link: Management of Plant-Parasitic Nematodes in Florida Peanut Production).

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 a susceptible cultivar with nematicide application. (For an example, follow this link to earlier article on Nematicides and Resistant Cultivars in Peanut Production)

In recent years, the number of peanut cultivars breeder-designated root-knot nematode resistant has increased (Table 1). The primary aims 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, and newer cultivars have had limited testing in Florida. Therefore, small plot trials were conducted to compare these resistant cultivars under severe pressure from peanut root-knot nematode.

Trials were conducted at West Florida Research and Education Center (WFREC) in 2023 and 2024, as well as North Florida Research and Education Center-Suwannee Valley (NFREC-SV) in 2024. The resistant cultivars listed in Table 1 were included in the trials, except for GA 23RKN, which was not included either year, and GA 22MPR, that was only included in 2024. Resistant cultivars were compared to root-knot nematode susceptible GA 06G with in-furrow Velum nematicide at 6.5 fl. oz/or GA 06G without nematicide.

Figure 1. Root-knot nematode susceptible cultivars exhibiting foliar yellowing (chlorosis) compared with green resistant cultivars in small plot trial at NFREC-SV in September 2024.

–

Resistant cultivars manage root-knot nematode infection and galling damage

TifNV-HiO/L, TifNV-HG, GA 14N, and GA 22MPR were very effective at minimizing root-knot nematode infection during the season (Figure 2) and mitigating galling at the end of the season (Figure 2). In contrast, in-furrow Velum nematicide was not effective at mitigating root-knot nematode infection or belowground symptoms in this study (Figures 2 and 3). Unlike other cultivars marked as resistant, ACI N104 showed a more intermediate level of resistance. It did not reduce midseason infection relative to the susceptible GA 06G (Figure 2) but had some efficacy at managing pod galling at the end of season (Figure 3). For nematode data not shown (midseason root-knot nematode eggs for NFREC 2024 as well as pod galling and harvest root-knot nematode soil counts for WFREC 2024), values were low and not affected by treatments. This was likely due to very hot and dry conditions before the affected assessments.

Figure 2. Midseason (6 weeks after planting) root-knot nematode egg population densities from roots as influenced by cultivars or in-furrow Velum nematicide. Treatments that do not share a letter are significantly different (Fisher’s protected LSD, P<0.05)

–

Figure 3. Root-knot nematode galling of pods at harvest (mean of 10 plants/plot) as influenced by cultivars or in-furrow Velum nematicide. Treatments that do not share a letter are significantly different (Fisher’s protected LSD, P<0.05)

–

Resistant cultivars can also help manage peanut root-knot nematode for the next crop

Resistant cultivars—except ACI N104—also consistently reduced final root-knot nematode soil abundances (Figure 4). 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.

Figure 4. Root-knot nematode soil population densities at harvest as influenced by cultivars or in-furrow Velum nematicide. Treatments that do not share a letter are significantly different (Fisher’s protected LSD, P<0.05)

–

Resistance generally improved yield, but there was inconsistency

Yield at WFREC in 2023 (not shown) was very poor at around 1500 lb/a 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 GA 06G (Figure 5). GA 22MPR did not perform as well as the top-yield cultivars at WFREC in 2024, likely because the stand was poor for GA 22MPR at that location. In contrast, at NFREC, TifNV-HG and GA 22MPR yielded better than the other resistant cultivars or GA 06G. TifNV-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, due to prior consistent yield 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, starting on limited acreage, especially 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 at The Florida Peanut Team Website.

Figure 5. Peanut yield as influenced by cultivars or in-furrow Velum nematicide. Treatments that do not share a letter are significantly different (Fisher’s protected LSD, P<0.05)

Zane Grabau
Latest posts by Zane Grabau (see all)