2020 Progress Made Possible Through Oklahoma Peanut Commission and National Peanut Board Support

• A total of 34 breeding lines and reference cultivars were evaluated at the Caddo Research Station for agronomic characteristics and soilborne diseases (Sclerotinia blight and pod rot).
• The runner trial included Lariat, Tamrun OL11, FloRun ‘107’, eight breeding lines from the United States Department of Agriculture-Agricultural Research Service (USDA-ARS) and oneInternational Peanut Group breeding line. The Spanish/Valencia trial tested OLé, Schubert, Span-17, Valencia C, two USDA-ARS Spanish breeding lines and two New Mexico State University Valencia breeding lines. The Virginia trial evaluated 14 entries: Jupiter, ACI 351, Contender, Venus, Walton, IPG 464 and eight breeding lines from North Carolina State University.
• The Spanish/Valencia plots were dug 131 days after planting (DAP). Runner and Virginia plots were dug 170 DAP. Environmental conditions in September and October were favorable for Sclerotinia blight. Low levels of pod rot were observed in the advanced breeding line/cultivar trial.
• Numerically, the top two runner entries for revenue were Lariat ($992 per acre) and ARSOK-R92-13 ($925 per acre). ARSOK breeding line R96-8 had the least Sclerotinia blight at 7%. In contrast, the susceptible control, FloRun ‘107’, had 54% disease.
• For the Spanish/Valencia entries, ARSOK-S96-5 ($629 per acre), Span-17 ($624 per acre) and ARSOK-S88-2 ($615 per acre) had the highest numerical crop values. Span-17 had relatively low but significantly more Sclerotinia blight than other entries.
• In the Virginia trial, the three highest numerical crop values were from Contender, NC17EX and Jupiter ($895, $830 and $830 per acre, respectively). No significant differences in Sclerotinia blight were observed. The Virginia entries had significant differences in pod sizes (number per ounce) and distribution of pod size classes by weight.
• Eight Virginia entries were tested in the pod rot nursery: Jupiter, ACI 351, Contender, IPG 464, NC1EX, NC2EX, NC7EX and NC17EX. Moderately high levels of pod rot were observed, but there were no significant differences among the entries. 

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 2020, 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 agronomic characteristics (e.g., yield and seed grade) and resistance to soilborne diseases 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.

 

Methods and Field Conditions for Evaluating Advanced Breeding Lines and Cultivars

A total of 34 breeding lines and reference cultivars (12 runner, eight Spanish/Valencia and 14 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-ft 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 on May 18. The Spanish/Valencia entries were dug on Sept. 25 – 131 days after planting – and threshed on Sept. 29. The runner and Virginia fields were dug 170 days after planting on Nov. 3 and threshed on Nov. 5 and 6. 

 

Due to limited inoculum, three of the four blocks were inoculated with pure sclerotia of Sclerotinia minor on Aug. 31. 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. Environmental conditions in 2020 were favorable for Sclerotinia blight due to cooler-than-average temperatures in September and October, in addition to above-average precipitation in September (Table 1). Additional water (0.5 inches to 1 inch) was applied to the plots 20 times between June 2 and Sept. 18 using a center pivot system. 

 

¹  Mean temperature and rainfall are for May 18 (planting date) to May 31 and Nov. 1-3 (last digging date). Departure from 15-year average includes all days in May.

²  Data from some days is not available due to incomplete Mesonet records. 

 

Ratings for Sclerotinia and southern blights were collected on Sept. 18 in the Spanish/Valencia plots and on Oct. 2 for the Virginia and runner plots. Disease incidence was measured by counting the number of 6-inch sections within each plot that had symptoms of Sclerotinia blight and southern blight. Little southern blight was observed. Spanish/Valencia plots were examined for pod rot three days after digging; Virginia and runner plots were rated for pod rot within three hours of digging.

 

Peanut grades were determined following USDA-Agricultural Marketing Service guidelines using one 200-gram samples from each plot. One 500-gram sample per plot was 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. 

 

Performance of the Runner Market Type Entries

Twelve runner peanut entries were evaluated (Table 2): high-oleic cultivars Lariat, Tamrun OL11 and the Sclerotinia blight-susceptible FloRun ‘107’, eight breeding lines from the ARS-Stillwater peanut program and one breeding line from Dylan Wann (International Peanut Group, Brownfield, Texas).

 

Statistical differences were found among runner entries for crop value, yield and all shelling characteristics. Numerically, the top two runner entries for revenue and yield were Lariat ($992 and 6,014 pounds per acre) and ARSOK-R92-13 ($925 and 5,602 pounds per acre). The lowest crop value and yield were obtained from FloRun ‘107’ ($651 and 4,054 pounds per acre). Breeding line ARSOK-R90-12 had the highest grade at 71.9%, and ARSOK-R96-8 had the lowest grade at 62.6%. ARSOK-R96-8 was most resistant to Sclerotinia blight with 6.7% disease incidence, and the susceptible control cultivar FloRun ‘107’ and IPG breeding line 08-1-0016 were least resistant. 

 

Table 2. Yield, grade, Sclerotinia blight and shelling characteristics in advanced runner and Spanish/Valencia breeding lines and commercial cultivars planted at the Caddo Research Station in Fort Cobb, Oklahoma on May 18, 2020.1

 

Performance of the Spanish/Valencia Market Type Entries

Two Spanish breeding lines from ARS-Stillwater and two Valencia lines from Naveen Puppala (New Mexico State University) were evaluated in addition to cultivars Valencia C, OLé, Schubert and Span-17. The 2020 contract price for Valencia peanuts was $750 per ton (Puppala, personal communication), but all entries were analyzed using the Spanish contract price of $475 per ton to facilitate comparisons. Significant differences among the Spanish and Valencia entries were found for all agronomic characteristics except visibly damaged kernels (Table 2). ARSOK-S96-5 produced the highest value crop and yield ($629 and 4,477 pounds per acre) and was significantly greater than the three Valencia entries. Span-17 and ARSOK-S88-2 had the highest seed grade, both at 65%, which was significantly greater than AROSK-S96-5 at 59%. Little Sclerotinia blight was observed, but Span-17 had more disease than the other entries.

 

Performance of the Virginia Market Type Entries

A total of 14 Virginia peanut entries were evaluated (Tables 3 and 4): Jupiter and high-oleic cultivars ACI 351, Contender, Venus, Walton and IPG 464; six early-maturing lines from Thomas Isleib (NCEX series, North Carolina State University); and two early-maturing lines from Jeffrey Dunne (N15041 and N16034, also NCSU). The Virginia entries differed statistically except in incidence of Sclerotinia blight, percentage small seed and visibly damaged kernels (Table 3). Numerically, the top three entries for crop value and yield were Contender ($895 and 5,421 per acre), NC17EX ($830 and 5,112 per acre) and Jupiter ($830 and 5,251 per acre). N16034 was significantly lower in grade than the other entries. Significant differences in number of pods per ounce were found for all categories of pod sizes (Table 4), as well as the distribution of pod sizes by weight (Figure 1). 

 

Table 3. Yield, grade, Sclerotinia blight and shelling characteristics of advanced Virginia breeding lines and commercial cultivars planted at the Caddo Research Station in Fort Cobb, Oklahoma on May 18, 2020.

 

¹  Entries sorted from highest to lowest contract revenue per acre from Table 3. Plots dug on Nov. 3 (171 days after planting). Numbers with the same lowercase letter within columns for each market type are not significantly different (α = 0.05).

²  Number of pods per ounce for pods riding slotted screens sized for super jumbo (40/64 x 3-inch slots), jumbo (37/64 x 3 inches), fancy (32/64 x 3 inches). Pass-through pods fit through 32/64 x 3-inch screen.

³  Percentage of pods by weight.

 

Figure 1.  Distribution of Virginia pod sizes by weight from the advanced breeding line/cultivar trials in 2018 to 2020.

 

Average Performance over the Past Three Years (2018-2020)

Seven runner, five Spanish and nine Virginia entries were evaluated from 2018 to 2020 (Table 5). In 2018, harvest dates for the runner, Spanish and Virginia plots were 141, 130 and 147 days after planting, respectively. In 2019, all market types experienced a severe early freeze before being harvested 162 days after planting. Little Sclerotinia blight was present in 2019.

 

When data from multiple years were combined, significant differences in Sclerotinia blight, yield and grade were found among the runner entries. All entries were better than the susceptible control, FloRun ‘107’, in Sclerotinia resistance. The highest numerical yields were obtained from Lariat and ARSOK-R92-13. Seed grades for ARSOK-R90-12 were significantly greater than FloRun ‘107’ and ARSOK-R93-10. Among the Spanish entries, Span-17 had significantly more Sclerotinia blight than other entries. No statistically significant differences were observed among entries in yield, but Span-17 had better seed grade than Schubert and OLé. The nine Virginia entries were not significantly different in Sclerotinia blight. NC17EX had the highest numerical yield at 4,792 pounds per acre, which was greater than NC7EX and NC22EX. The grades obtained from NC7EX and NC17EX were significantly higher than Jupiter.

 

Table 5.  Three-year averages for Sclerotinia blight, yield (pounds per acre) and seed grade in advanced breeding lines and commercial cultivars at the Caddo Research Station in Fort Cobb, Oklahoma (2018-2020).¹

 

Pod Rot Nursery Results

For the pod rot nursery, a total of eight Virginia entries (ACI 351, Contender, Jupiter, IPG 464, NC1EX, NC2EX, NC7EX and NC17EX) were evaluated in a field where moderately high levels of pod rot were observed in 2017 (Table 6) and where pod rot-susceptible germplasm lines are planted every three years. The field was planted on May 18, using a randomized complete block design with four blocks. Plots were managed for leaf spots, Sclerotinia and southern blights and were irrigated identically to the advanced line/cultivar plots. Plots were dug on Oct. 16, 152 days after planting, and evaluated for pod rot within three hours after digging by estimating the percentage of discolored pods. Moderately high levels of pod rot were observed (Table 6), but no significant differences were found among the Virginia entries. Numerically, NC17EX and Jupiter had the highest levels of pod rot at 54% and 53%, respectively. Entries with numerically less pod rot included NC2EX and NC17EX, both at 36%.

 

Table 6. Pod rot in Virginia entries planted in the pod rot nursery and cultivar/advanced breeding line trial at the Caddo Research Station in Fort Cobb, Oklahoma in 2019 and 2020.¹

¹ Numbers with the same lowercase letter within columns for each market type are not significantly different (α = 0.05).
² Percentage of pods with symptoms of pod rot estimated within 3 days after digging.

 

 

Additional Acknowledgments

We thank Angela Harting and Lisa Myers 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 and Golden, and Maria Balota (Virginia Tech) provided seed of Walton. This research is supported by USDA-ARS Current Research Information System Project No. 3072-21220-008-00D. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the USDA, which is an equal opportunity provider and employer.