Mississippi Delta Community College

This study explores the phenotypic, genotypic, and serological differences among Edwardsiella ictaluri isolated from farm-raised catfish Ictalurus spp. and ornamental fish (Danio spp. and Puntius tetrazona) in the USA. Plasmid analyses revealed diverse plasmid profiles, with varied antimicrobial resistance genes indicating diverse resistance and virulence mechanisms. Analysis of complete genome sequences revealed multiple virulence factors, including the Type III and Type VI secretion systems, with varied presence between the catfish and ornamental derived strains. Molecular analyses, including multi locus sequence analysis (MLSA) and repetitive extragenic palindromic-PCR, identified discrete genotypic differences, identifying an optimally informative MLSA scheme for demonstrating intraspecific relationships among E. ictaluri conspecifics. Serological assessments revealed marked differences between catfish and ornamental isolates, indicating distinct antigenic profiles and suggesting that E. ictaluri vaccines derived from catfish isolates may have limited efficacy against ornamental isolates, supporting anecdotal reports from the industry. This research advances our understanding of this important bacterial fish pathogen, laying a foundation to help guide approaches in vaccine design and disease mitigation in catfish and ornamental fish moving forward.

Dero digitata, a freshwater oligochaete worm found worldwide, serves as the definitive host for the myxozoan Henneguya ictaluri, the cause of proliferative gill disease (PGD) in ictalurid catfish. The study objectives were to describe pathologic changes associated with developing actinospores within D. digitata from a commercial catfish pond during an active PGD outbreak. Specific in situ hybridization probes identified H. ictaluri, Henneguya exilis, and Raabeia-type TGR 2014 actinospore development in pure infections associated with intestinal epithelial hypertrophy, hyperplasia, and vacuolation. Results support findings from other myxozoans demonstrating clonal expansion of myxozoan populations occurs through asexual reproduction of the oligochaete host.

Biostimulants have garnered significant interest due to their potential to enhance crop productivity while optimizing nitrogen (N) uptake and nitrogen use efficiency (NUE). However, field research testing their efficacy in corn ( Zea mays. L) production remains largely unexplored. Therefore, a field study was conducted in 2022 and 2023 in Mississippi (MS). A split plot design was implemented, with N rates as the main plot including 0 (control), 90, 180, 269 kg N ha −1 at Starkville, while Stoneville included an additional rate of 224 kg N ha −1 . The subplot consisted of seven treatments, including a no biostimulant (check) and six microbial biostimulants (Source Corn®, Envita®, iNvigorate®, Blue N®, Micro AZ™, and Bio level phosN®) applied either as foliar at V4-V5 growth stages or in-furrow at planting. Nitrogen rates positively affected grain yield at all three site-years, whereas biostimulants effects on grain yield were only observed at one site (Stoneville 2022). Moreover, these differences only existed between six biostimulants and they were not significantly different from check plot with no biostimulant. Higher N rates reduced the efficiency of grain production in terms of NUE parameters and N uptake, showing a consistent inverse trend across all site years. This study observed minimal synergistic benefits of microbial biostimulants, despite evaluating their effectiveness alongside varied N rates. Further research testing diverse biostimulant categories with varied dosages and application timings is warranted to confirm their potential benefits for higher productivity and agricultural sustainability. • Biostimulants were unable to improve corn grain yield. • Sites responded differently to nitrogen rates in terms of corn grain yield. • Maximum recovery efficiency of nitrogen was obtained at 90 kg N ha −1 .

In the southern United States, thrips are a significant early season pest of cotton. In the United States, in 2022, 98% of cotton acres were infested with thrips, and, of those acres, 45% were treated for thrips. Thrips injury resulted in over $113 million dollars in losses plus control costs to the cotton industry in the United States that year. A new Bacillus thuringiensis trait known as ThryvOn has been commercialized to provide control against thrips. There is ongoing debate about the need for an insecticidal seed treatment to improve thrips control on ThryvOn varieties. Field studies were conducted to determine if the addition of an imidacloprid seed treatment improved efficacy against tobacco thrips and to determine if reduced rates of seed treatments (0, 25, 50, 75, and 100% of the labeled rate) provided benefits for thrips control in ThryvOn cotton. To control for infestation pressure, a complementary greenhouse study was conducted using the same treatments under controlled conditions. Imidacloprid provided only a limited benefit for improved management on ThryvOn cotton in the greenhouse study, but no benefit in the field study. Efforts in pest surveillance should be continued in ThryvOn cotton to allow for foliar applications when warranted based on established thresholds. No conclusions can be drawn about the benefits of an imidacloprid seed treatment for resistance management in ThryvOn cotton from this study, but these data suggest that any benefit would be minimal.

No‐tillage (NT) management protects soil from wind and water erosion and improves soil health. Uncertainty in farm production under location‐specific NT practices poses challenges to adopting it by the farming community. To address this challenge, a 4‐year study (2019–2022) was conducted on farm‐size plots (∼1.25 ha) focused on comparing soybean (Glycine max [L.] Merr.) yield and soil health benefits of an NT system with a conventional tillage (CT) system in silt loam soil. The NT and CT plots were under corn production over the previous 11 years. Compared to CT, in the 0–20 cm layer, soil bulk density (ρ), total nitrogen (TN), and soil organic carbon (C) increased, but field‐saturated hydraulic conductivity (Kfs) decreased in the 10 cm below the soil surface under NT. Higher ρ was also noticed in the 10–30 cm soil. There were no significant differences between NT and CT in water stable aggregate stability for 0.25–0.5, 0.5–1.0, 1.0–2.0, and 2.0–4.0 mm aggregate classes. While the higher ρ and lower Kfs under NT can potentially restrict plant root expansion, the beneficial effects of C and TN appear to make up for those adverse effects, culminating in comparable seed yield returns. Over four years, soybean seed harvested from NT (5440 kg ha−1) was 1% less than CT (5480 kg ha−1). Therefore, adopting the NT system increases net returns by reducing tillage‐associated expenses without compromising soybean yields in the Lower Mississippi Delta region, which can improve soil and water conservation.

Abstract Planting date, row configuration, and seeding rate are three critical factors in obtaining maximum soybean [Glycine max (L.) Merr.] grain yield and can vary based on soil texture. Therefore, two studies were conducted at the Delta Research and Extension Center in Stoneville, MS. The first study was conducted from 2019 to 2021 and sought to determine the effects of planting date (optimal and delayed 21 days), and row configuration (single‐, twin‐, and triple‐row) on soybean growth, development, and grain yield. The second study was conducted in 2021 with three site‐years to determine the effects of seeding rate (130,000, 180,000, and 220,000 seeds acre−1) in a triple‐row configuration on soybean grain yield compared to a single‐row configuration at 130,000 seeds acre−1 on two soil textures (silt loam and clay). Both studies were repeated on silt loam and clay soil textures in every site‐year. In the first study, the optimal planting date increased soybean grain yield regardless of soil texture. On both soil textures, twin‐ and single‐row configuration yields were equivalent, but triple‐row configuration reduced soybean grain yield up to 9%. Similarly, triple‐row configuration reduced soybean density and height at R3 and R8 growth stages. In the second study, increasing triple‐row configuration soybean seeding rate by at least 38% provided similar soybean grain yields to a single‐row configuration at 130,000 seeds acre−1. These data indicate that triple‐row soybean planting configurations do have some benefits, but that future research should focus on equipment limitations experienced in the current research.

Abstract Objective The Delta Select line of Channel Catfish Ictalurus punctatus was established in 2006 and has undergone five generations of genetic selection, specifically targeting increased growth rate and carcass yield, and was released to U.S. catfish farmers in 2020. While improvements in growth rate and carcass yield have been confirmed, performance for other important production traits has yet to be evaluated. Infectious disease, particularly bacterial infections caused by Edwardsiella spp., cause significant economic losses to catfish producers in the southeastern United States. Given the economic consequences of these bacterial pathogens, experimental infectivity trials were conducted comparing susceptibility to Edwardsiella spp. between the Delta Select line and a randomly bred line of Channel Catfish originating from the same base population (Delta Control line). Methods Twenty-six full-sib families from each line were used in infectivity trials consisting of a high and a low dose of E. ictaluri (immersion challenge: high dose = 1.6 × 107 CFU/mL, low dose = 8.0 × 106 CFU/mL) and E. piscicida (intracoelomic challenge: high dose = 6.3 × 105 CFU/fish, low dose = 1.9 × 105 CFU/fish). Result The high challenge dose resulted in the highest mortality for both pathogens (p < 0.001), regardless of selection line. There was no significant difference in cumulative percent mortality between the Delta Select and Delta Control lines following the E. ictaluri challenge at either dose (p = 0.55). Delta Selects had reduced mortality (p < 0.001) in response to E. piscicida challenge compared with the Delta Controls, regardless of dose. Conclusion These results indicate that selection for increased growth rate and carcass yield in the Delta Select Channel Catfish line did not negatively impact resistance to E. ictaluri while potentially improving resistance to E. piscicida.

Corn (Zea mays) biomass accumulation and nutrient uptake by the six-leaf collar (V6) growth stage are low, and therefore, synchronizing nutrient supply with crop demand could potentially minimize nutrient loss and improve nutrient use efficiency. Knowledge of corn's response to nutrient stress in the early growth stages could inform such nutrient management. Field studies were conducted to assess corn recovery from when no fertilizer application is made until the V6 growth stage, and thereafter, applying fertilizer rates as those in non-stressed conditions. The early season nutrient stress and non-stress conditions received the same amount of nutrients. As the availability of nutrients for plant uptake is largely dependent on soil moisture, corn recovery from the early season nutrient stress was assessed under different soil moisture regimes induced via irrigation scheduling at 50% and 80% field capacity under overhead and subsurface drip irrigation (SSDI) systems. Peanut (Arachis hypogaea) was the previous crop under all conditions, and the fields were under cereal rye (Secale cereale) cover crop prior to planting corn. At the V6 growth stage, the nutrient concentrations of the early season-stressed crops, except for copper, were above the minimum threshold of sufficiency ranges reported for corn. However, the crops showed poor growth, with biomass accumulation being reduced by over 50% compared to non-stressed crops. Also, the uptake of all nutrients was significantly lower under the early season nutrient stress conditions. The recovery of corn from the early season nutrient stress was low. Compared to non-stress conditions, the early season nutrient stress caused 1.58 Mg ha-1 to 3.4 Mg ha-1 yield reduction. The percent yield reduction under the SSDI system was 37.6-38.2% and that under the overhead irrigation system was 11.7-13%. The high yield reduction from the early season nutrient stress under the SSDI system was because of water stress conditions in the topsoil soil layer. The findings of the study suggest ample nutrient supply in the early season growth stage is critical for corn production, and thus, further studies are recommended to determine the optimum nutrient supply for corn at the initial growth stages.