2022 Progress Made Possible Through Oklahoma Peanut Commission and
National Peanut Board Support

• A total of 43 breeding lines and reference cultivars were evaluated at the Caddo Research Station for agronomic characteristics and soilborne diseases (Sclerotinia blight and pod rot).
• The 16-entry runner trial included Lariat, FloRun ‘107’, Southwest Runner, ACI 080, ACI
  476, ACI 3321, IPG 914 and nine breeding lines from the United States Department of
  Agriculture-Agricultural Research Service. The 15-entry Spanish/Valencia trial tested six USDA-ARS Spanish breeding lines, four New Mexico State University Valencia breeding lines and the cultivars OLé, IPG 3628, Schubert, Span 17 and Valencia C. The Virginia trial evaluated 12 entries: Jupiter, ACI 351, Contender, Comrade, and two breeding lines from North Carolina State University and six from USDA-ARS.
• All plots were planted in June to ensure green foliage was present in case conditions were favorable for Sclerotinia blight in late September to October. Plots were planted on June 6 and dug 148 days after planting (Oct. 31). The season was marked by unusually high average temperatures for July (5 degrees above 15-year mean) and below-average rainfall from July to September. The 2022 disease trial had a total of 3,203F degree days.
• Numerically, the top two runner entries for revenue were Lariat ($1,270 per acre) and ARSOK R109-1 ($1,241 per acre) at a contract price of $675 per ton. Average seed grade varied among entries from 72 to 61%. Moderately high levels of Sclerotinia blight were observed in mid-October, and the most resistant entries included Southwest Runner (10%), ARSOK R96-8 (18%) and Lariat (25%). Little pod rot was observed.
• OLé and ARS Spanish breeding lines S105-2E, S105-4E and S96-5 had the highest numerical crop value and yields when priced at $700 per ton (>$1,150 and >4,875 lbs. per acre). As in past years, Valencia entries generally yielded less than most Spanish entries. High levels of Sclerotinia blight were observed in the small-seeded runners Span 17 and IPG 3628 (54 and 80%, respectively). Little Sclerotinia blight (<12%) was present on the Valencia and true Spanish entries.
• All Virginia entries yielded above 4,300 lbs. per acre except ACI 351, but average seed
  grade was relatively low, ranging from 61 to 67%. Numerically, entries with the three highest crop values were ARSOK V98, Comrade and ARSOK V99 (>$1,090 per acre). Sclerotinia blight was highest in ACI 351, Jupiter and Comrade (>58%) and lowest in ARSOK V99 (6%). Little pod rot was observed. The entries differed significantly in pod size distribution, and Comrade had the largest percentage of super jumbo pods by weight.
• Little pod rot was present in the Virginia pod rot nursery, and high levels of root-knot nematodes were present in the disease trial field.

A major goal of the ARS peanut research program in Stillwater is to develop and release high-oleic peanut cultivars for the Southwest with improved yield, disease resistance and seed characteristics. In 2022, we evaluated commercial and advanced breeding lines of runner, Spanish/Valencia and Virginia peanuts in small plots at Oklahoma State University's Caddo Research Station in Fort Cobb. The objectives of these field studies were: 1) to compare advanced breeding lines to commercially available cultivars for resistance to Sclerotinia blight and agronomic characteristics, such as yield and seed qualities and 2) to evaluate a selection of Virginia entries for pod rot resistance in fields where soilborne levels of the pathogens causing peanut pod rot were promoted by planting susceptible genotypes the previous year.

 

Methods and Field Conditions for Evaluating Advanced Breeding Lines and Cultivars

A total of 44 breeding lines and reference cultivars (16 runner, 15 Spanish/Valencia and 12 Virginia market types) were evaluated. Runner and Virginia peanut market types were each grown and evaluated separately, but Spanish and Valencia entries were combined in the same field and analyzed together. All advanced breeding lines were high oleic. Each entry was planted at a density of five seeds/ft in plots consisting of two 15-foot-long rows with 36-inch-wide beds. A randomized complete block design was used by dividing the field into four sections (blocks) to account for potential disease gradients and environmental variables. All plots were planted approximately one month later than normal (June 6) to ensure green foliage was available for late-season epidemics of Sclerotinia blight. All plots were inverted on Oct. 31, 148 days after planting and threshed on Nov. 2-3. The pod rot nursery was planted on June 27 to reduce the number of volunteers, and plots were dug on Oct. 26.

 

Additional water was applied to all plots 19 times (total 10.85”) between June 17 and Oct. 14 using a center pivot system. Each row in the two-row plots was inoculated with 0.5g of Sclerotinia minor sclerotia on Sept. 7. Fields were managed for weeds, foliar diseases and southern blight (caused by Athelia rolfsii) following Extension recommendations but were not managed for Sclerotinia blight, pod rot or nematodes. Entries were evaluated for Sclerotinia and southern blights on Sept. 30 and on Oct. 12 and 14. Disease incidence was measured by counting the number of 6-inch sections within each plot that had symptoms of Sclerotinia blight and southern blight. On Oct. 18, approximately 10 soil cores were collected near the taproots from three plots planted to Jupiter for nematode counts. All plots were examined for pod rot on the same day the plants were inverted.

 

Peanut grades were determined following USDA-Agricultural Marketing Service guidelines using two 200-gram samples from each plot. Two 500-gram samples per plot were used to determine pod sizes in the Virginia entries. Yield was adjusted by factoring in the area lost by plots in the path of the center pivot wheels. Data were analyzed using one-way ANOVA in PROC GLIMMIX of SAS (ver. 9.4). The Type I error rate for pairwise comparisons of breeding lines and cultivars was controlled at α = 0.05 using the ADJUST=SIMULATE option.

 

Summary of 2022 Field Conditions

A total of 3,203-degree day heat units (in Fahrenheit) accumulated for the 2022 disease trial. The season was characterized by unusually high temperatures for July (+5F above average) and below average rainfall from July to September (Table 1). Cooler evening temperatures in September and October facilitated the development of Sclerotinia blight. Little southern blight and pod rot were observed. The nematology lab at Oklahoma State University found 276 root-knot nematodes per 100 cc soil in the soil cores, levels considered to be well above recommended thresholds (Nathan Walker, pers. communication). Little pod rot was observed in the Virginia pod rot nursery, so ratings were not taken.

 

Performance of the Runner Market-Type Entries

Sixteen runner peanut entries were evaluated (Table 2):

• High-oleic cultivars Lariat, ACI 080, ACI 476, ACI 3321 and IPG 914
• The Sclerotinia blight-susceptible and resistant cultivars FloRun ‘107’ and Southwest Runner, respectively, for reference
• Nine breeding lines from ARS-Stillwater

Statistical differences were found among runner entries for crop value, yield and all-shelling characteristics (Table 2). Numerically, the top two runner entries for crop value or revenue – a combined measure of yield and seed grade – and yield were Lariat ($1,270 per acre; 5,324 lbs. per acre) and ARSOK R109-1 ($1,241 per acre; 5,215 lbs. per acre) at a contract rate of $675 per ton. Average seed grade among entries was 68%, and six entries produced seed grades of 70% or higher: Lariat, ACI 080 and ARSOK lines R109-1, R106-9, R107-2 and R93-1. High levels of Sclerotinia blight were observed in the susceptible control FloRun ‘107’ (88%) and in all ACI cultivars, IPG 914 and multiple breeding lines (≥50%). The most Sclerotinia-resistant entries were Southwest Runner, ARSOK 96-8 and Lariat (10 to 25%).

Many of the same entries from 2022 were also evaluated in 2021, albeit in a field that consistently produces lower yields (Table 3). Over both years, Lariat produced the highest numerical yield and grade. Conditions in 2021 were unfavorable for Sclerotinia blight, but the most susceptible and resistant entries over both years were the control entries FloRun ‘107’ and Southwest Runner, respectively.

 

Performance of the Spanish/Valencia Market-Type Entries

Six Spanish breeding lines from ARS-Stillwater and four Valencia lines from New Mexico State University were evaluated in addition to cultivars Valencia C, OLé, Schubert, IPG 3628 and Span 17 (Table 4). The 2022 contract price for Valencia peanuts was $950 per ton (N. Puppala, pers. communication), but all entries were analyzed using the Spanish contract price of $700 per ton to facilitate comparisons between the market types. In 2022, yields and crop values from several Spanish entries numerically exceeded those from the small-seeded runners Span 17 and IPG 3628. Yields in Span 17 and IPG 3628 were likely limited due to being severely affected by Sclerotinia blight (54 and 80%, respectively). In comparison, relatively little Sclerotinia blight was observed on Spanish and Valencia entries. As in past years, Valencia entries generally yielded less than Spanish entries. While yields in 2021 were markedly less than in 2022, the Spanish/
Valencia entries performed similarly over both years (Table 5).

 

Performance of the Virgina Market-Type Entries

A total of 12 Virginia peanut entries were evaluated in 2022 (Table 6):

• Jupiter and high-oleic cultivars ACI 351, Comrade and Contender
• Two early-maturing breeding lines from North Carolina State University, N15041 and N17045
• Six USDA-ARS breeding lines

 

The Virginia entries differed statistically in all categories except visibly damaged kernels (Table 6). At a contract price of $675 per ton, six entries (Comrade, Contender and ARSOK lines V98, V99, V103-2 and V101-1) had crop values significantly greater than ACI 351 (>$1,060 vs. $794 per acre). Despite being planted in June, crop yields for six entries exceeded or approached 5,000 pounds per acre. However, seed grades were low, averaging 64%, and Comrade had the highest grade at 67%. Several entries, including Comrade and ACI 351, were as susceptible to Sclerotinia blight as Jupiter (>58%). The most resistant Virginia entry was ARSOK V99 at 6% disease incidence. Significant differences were observed among the Virginia entries for number of pods per ounce for each of the pod size classes (Table 6) in addition to the distribution of pod
size classes by weight (Figure 1). Comrade, ACI 351, V103-3, V103-1 and Jupiter had the greatest percentage of super jumbo pods (≥65%).

 

Over the past two years, ARSOK V99 had the highest average yield (4,332 pounds per acre) and the least amount of Sclerotina blight (7%; Table 7). The two-year seed grade average in Comrade (69%) was significantly greater than in Jupiter (63%). All Virginia entries except ARSOK V99 and V98 appeared moderately or highly susceptible to Sclerotinia blight.

 

Acknowledgments

We thank Angie Harting, Lisa Myers, Karen Weckler and Kyren Bunyard at USDA-ARS, and Robert Weidenmaier, Harley Houston and Brennan Leighton at the Caddo Research Station, for invaluable technical support. Seed for several commercial lines were originally provided by Birdsong, Golden and the International Peanut Group. University breeders Naveen Puppala (New Mexico State University) and Jeff Dunne (North Carolina State University) provided Valencia and Virginia breeding lines, respectively.