Created in 1968, the Multistate Hatch S-1079, S-1059, S-1038, S-1003, S-140 [known as the Peanut Variety and Quality Evaluation (PVQE)] has provided variety testing for over 50 years. This Multistate has been recognized as a strong data support program for the virginia-type (market types are lowercase by convention) cultivar development. The project also provided a forum for various segments of the peanut production, shelling, and processing industries to express the industry’s emerging needs through the annual meetings of the PVQE Advisory Committee.  Virginia-type peanut (Arachis hypogaea L. subsp. hypogaea var. hypogaea) is distinct from other peanut market types, i.e., runner, spanish and valencia. This distinction is from the seed and pod size, which are larger for virginia than for other types. For example, pod count is less than 318 kg^-1 when sized on 15.9-mm by 76.2-mm screen, and seed is an average of 1055 kg^-1 for virginia type when compared with 477 kg^-1 and 1830 kg^-1, respectively, for the other peanut types. Indeed, the virginia-type peanuts are almost twice the weight of the other types, and have high content of extra-large kernels (ELK), i.e. seed not passing a 25.4-mm by 8.5-mm screen, for which farmers receive premiums.  For an average return of $355 ton^-1 of farmer stock peanut, approximately $20 ton^-1 is from the ELK content. 

Significance of the Virginia-type peanut in U.S. peanut production: Virginia-type peanut is grown in Virginia and the Carolinas (VC) as well as the Southwest (SW). In the VC region, peanut is an important cash crop with annual acreages ranging from 175,000 to 230,000 ac. For example, in 2021, total peanut production of this region was 457 × 10³ tons, with a $215 million value from 210,000 harvested acres (USDA-NASS, 2022). From this, 80% is attributable to virginia-type cultivars. Gourmet processing trade sets this region, and Virginia in particular, apart from the other peanut growing states since the majority of these firms are located in Virginia. For this market, it is the largest of the ELK that carry the highest value of the virginia-type peanut, called Super ELK (SELK), i.e. seed not passing a 25.4-mm by 9.6-mm screen. In the SW, virginia-type is grown in Texas and Oklahoma on acres ranging from 20 to 45% of the total certified peanut acreage (Chamberlin et al., 2019, 2022). For example, in 2020, Texas planted 47,232 acres of virginia-type of the total 221,746 production acres (survey conducted by the Texas Peanut Producers Board and Bob Whitney, 2022). In these states, a large portion of the virginia-type peanut is exported. For these markets, pod and seed size, i.e. high content of ELK, and pod color (i.e. pod brightness at least 45 based on Hunter L. score) are important (Chamberlin et al., 2019). For decades, PVQE provided, in addition to yield, information on pod and seed size and quality, i.e. farmer stock grade, and financial return was estimated from yield and grade for each tested line. Pod color has been also measured and, along with yield, grade and economic return, this information was annually published within the PVQE Agronomic and Grade Data reports (Balota et al. 2022a).

The need to maintain quantity and quality: Since the early years of the Multistate, estimated dollar returns to the grower increased from $600 per acre in late 80’ s and 90’ s to $850 per acre with the release of Bailey II in 2019 in the VC region. Because the dollar return is calculated from a complex USDA formula using yield and grade characteristics, this is an indication that both yield and grade are important to consider for further improvement of virginia-type peanut production.  For example, average yield of the cultivars released after being tested in the PVQE Multistate went from 4,000 pounds per acre for cultivars released in early 90’ s to 6,000 pound per acre for the recent releases. Similarly, ELK content of NC-V 11, released in 1991, was 34.2% while that of Bailey II was 47.7%.

Both regions grow virginia-type cultivars with over 74% content of oleic fatty acid (C18:1), or “high oleic” cultivars. The high oleic oil chemistry, i.e. increased C18:1 and decreased linoleic (C18:2) fatty acid content, improves peanut shelf life, reduces rancidity, and increases safety for consumers.  Earlier research showed that high oleic peanut has improved oxidative stability and longer shelf life than non-high oleic peanut.  For example, roasted in shell peanuts with 50% C18:1 reached a Peroxide Value (PV) of 20 meq kg^-1 (as indication of oxidation) after only 2 wks. of storage.  However, peanuts with 80% oleic fatty acid did not reach 20 meq kg^-1 until after 40 wks. of storage (Mozingo et al., 2004).  Since the deployment of S-1059, all lines tested in the PVQE have been high oleic. Recently released cultivars after being tested in the PVQE, i.e. ‘N.C. 21’, ‘N.C. 20’, ‘Walton’, ‘Bailey II’, ‘Emery’, ‘Sullivan’ and ‘Wynne’, are also high oleic. Blanchability is the seed capacity to maintain intact after testa has been removed and represents an important characteristic in peanut processing. Information on oil profile and blanchability was annually included for each breeding line within the PVQE Quality Data reports (Balota et al. 2022b).

The need to improve sustainability: Drought significantly limits peanut production in the VC and SW.  In the SW, the Ogallala aquifer (the only source of irrigation) is declining at a rate of 0.3 m per year, which will cause depletion within the next 30-40 years (Paxton Payton, personal communication, 2019). This decline is already reducing the ability to irrigate at critical growth stages and when temperature exceeds 40 °C. Similarly, in the VC region, precipitation distribution is irregular and often deficient during the summer months.  Concurring with increasingly higher summer temperatures, this leads to frequent droughts which may affect peanut yield, grade, C18:1 content, and economic return in otherwise “rainy” years (Balota et al., 2015; Ramsey et al., 2020; Singh et al., 2014).  In particular, ELK and SELK require ample amounts of water to fill the seeds. Supplementing water through irrigation is an option, but only 10% of the peanut land is irrigated in the VC region.

Additionally, adjusting planting time to avoid drought can enhance the impacts of periodic extreme temperatures at critical flowering times. Therefore, improving peanut yield and quality during drought and extreme temperature episodes in rainfed production is now a priority for peanut production in the U.S.  

Within previous years of uniform cultivar trials, we have identified and released three breeding lines and cultivar ‘Walton’ expressing drought tolerance, i.e., relatively high yields under drought (Balota et al., 2021; Balota & Isleib, 2020; Balota et al., 2015; Tallury et al., 2014). Since deployment of S-1079 and leveraging PVQE efforts with a collaborative project with North Carolina State University (NCSU) (USDA NIFA AWARD # 2016-08666), we have identified several genomic regions and markers associated with drought tolerance traits in peanut (Kumar 2022) and are poised to complete similar work with heat stress tolerance traits. Through collaborative work with Texas A&M University, Oklahoma State University, and USDA-ARS we also leveraged efforts to develop high-throughput methods to phenotype drought and heat stress tolerance (NIFA-AFRI grant no.- 2017-67013-26193) (Sarkar, 2020). Within the current S-1079, we implemented rainout shelter testing for selection of peanut lines tolerant to heat and drought, but this method only allows for testing a limited number of lines at one location. Therefore, moving efforts towards use of “smart” technologies, as proposed in the multi-disciplinary and collaborative effort with Clemson University, NCSU, and Virginia Tech (NIFA-AFRI grant no.-2023-67013-39624) is the next logical step we propose during 2023 – 2028 stage of the project.

The need to exploit genetic and physiological mechanisms: Global increases in temperature and drought are major threats to crop production globally (Lesk et al., 2021). A combination of drought and heat stress can impact a number of physiological processes important in plant development and reproduction. In particular, sub-lethal elevated temperatures can directly impact yield by affecting the timing and production of flowers as well the viability of pollen (Paupiere et al., 2014) and these impacts can be compounded when coupled with drought (Prasad et. Al, 2008). Unraveling the genetic and physiological mechanisms that govern plant responses to these environmental stressors is central to developing crops that are climate adapted or resilient. This is a pressing problem in climate sensitive crops like peanut, where subtle shifts in temperature are threating global production (Ramsey et al., 2022). Yet, improving peanut yield and quality during periodic temperature elevation and drought stress has been identified to be of critical importance for the peanut stakeholders in the USA to maintain their competitiveness in the marketplace. The magnitude of change in the warmest periodic 5-day 1 in 10-year heat event is projected to be ca. 6^°C (U.S. Climate Info 2017). This increase early in pollen development has been shown to have significant impacts on yield in peanut and other legume crops, even over short durations (Prasad et al., 1999). Coupled with late season drought—the most important yield and quality limiting factor in peanut production worldwide (Songsri et al., 2008)—peanut and other crops face constraints during early flowering from heat stress and during pod filling from drought (Prasad et. al, 2008).

While this is true for the major peanut growing regions in the US, it is particularly true for peanut grown in the VC region. The predominant type of peanut grown here is the large seeded virginia-type or “gourmet” (market types are lowercase by convention). Virginia market-type peanut has the largest seed size among all the peanut types grown in the USA, where a kilogram of “gourmet” peanut has about 1000 seeds and runner peanut has about 1900 seeds. Whether larger seed require more water for full development than smaller seed is not known; but it has been shown that spanish types known for their small seed size are more drought tolerant than virginia type peanut (Erickson and Ketring, 1985). Prasad et al., (1999) found that these two types are also prone to pollen declines under heat stress during early flowering. This timing is critical because it means that growers cannot overcome these two stressors with a simple shift in planting time. Historically the VC region has been classified as “sub-humid,” and little attention was paid to short-term drought episodes that can impact seed yield and quality. This oversight is particularly troublesome because the soils of this region are sandy resulting in rapid soil water depletion, which is exacerbated by recurrent intervals of low rainfall and periodic extreme heat events. In the VC region, 85% of peanut is rainfed, but drought stress-related research has been almost absent. Preliminary research determined that uneven rainfall distribution and summer heat events in the VC region can significantly limit peanut yield and production value up to $15,000,000 in otherwise “good rainy” years (Balota et al., 2016). Under these conditions, the most reliable solution for peanut producers to mitigate heat stress and combined heat and drought stress is to adopt tolerant cultivars.