Submitted to: Peanut Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/21/2017
Publication Date: 7/25/2017
Citation: Sorensen, R.B., Nuti, R.C., Holbrook Jr, C.C., Chen, C.Y. 2017. Peanut peg strength and associated pod yield and loss by cultivar. Peanut Science. 44:77-82. doi.org/10.3146/PS17-1.1.

Interpretive Summary: Variability in phenotypic peg strength may contribute to greater digging losses in some peanut cultivars. Previous research has shown that peg strength can vary due to agronomic practices, field condition, peg age, moisture content, peanut cultivar, and fungal. Other research showed that cultivar Georgia-06G had greater peg strength than either Georgia-09B or Tifguard. This same study showed that peanut yields were greater at early plant and harvest dates and decreased as the plant aged. Conversely, peanut pod loss was lower with early plant and harvest dates but increased with later harvest dates. At present, peanut breeding programs in the United States do not have stronger peg strength as a breeding objective. Therefore, the release of new cultivars with advanced genetic characteristics, i.e., increased yield, disease resistance, drought resistance, etc., has no existing data comparing peg strength with harvestable yield. The objective was to compare peg strength, pod yield, and pod loss of various released and advanced line peanut cultivars at two locations and harvested at various dates. Peanut cultivars selected in 2010 were Georgia Green (GG), Georgia Greener (GNR), Georgia-02C (02C), Georgia-06G (06G), Georgia-07W (07W), Florida-07 (F07), Tifguard (TFG), and the advanced breeding lines Exp27-1516 (EXP27) and TifGP-2. The same cultivars were used in 2011 plus Georgia-09B (09B) (Branch, 2010) and Georgia-10T (10T). The experimental design at both sites was a factorial design within randomized complete block with three harvest dates and four replications per cultivar. The soil at both locations was Tifton loamy sand (Fine-loamy, kaolinitic, thermic Plinthic Kandiudults) with 1-2% slope. There were three harvest dates each year. Harvest date 1, 2 and 3 were on average at 132, 146 and 157 days after planting (DAP) across both years and sites. At each harvest date, a minimum of six peanut plants from each cultivar and replication were hand dug. The samples were washed with tap water to remove any excess soil. Three peanut plants were separated from the total sample. Peanut vines were separated using scissors to remove excess stems and leaves. After removing excess leaves and branches, the pegs with the associated stems were placed in plastic bags and stored in a refrigerator. All samples were processed within two days of sampling. Each peanut pod was placed in a “U” shaped metal bracket that was attached to an electronic force gauge connected to a computer. The force gauge was adjusted to collect the maximum force needed to detach the peanut from the peg. The stem was pulled manually away from the pod at a steady force until the pod detached. Force data were then sent electronically to the computer. Electronic force data for each peg and eventually the total plot was named and saved into separate electronic files for retrieval and analysis. Peanut cultivars that tended to be in the top three spots of the greatest peg strength, greatest yield and lowest pod loss was 02C and 06G. Other cultivars may have had stronger peg strength, greater pod yield or lower pod loss but none were more consistent that these two cultivars across years, locations, and times of harvest. Pod yield and pod loss data for the 2010 and 2011 crop years and at both locations were analyzed using linear regression to identify possibly relationship between pod yield and pod loss. Linear regression analysis showed an r2=0.07 which implies small relationship between pod yield and pod loss. There was a better linear and non-linear (polynomial) relationship (r2=0.41 and 0.45, respectively) between harvest date and pod loss such that as time increased past the optimum harvest date pod loss increased by about 129 kg/harvest. The increased loss of pod after the optimum digging date for all peanut cultivars has been well documented by previous researchers, breed

Technical Abstract: Peanut (Arachis hypogaea L.) peg strength and associated pod yield and digging loss were documented for nine cultivars and two breeding genotypes across three harvest dates at two Southwest Georgia locations during 2010 and 2011. Cultivars selected were Georgia Green, Georgia Greener, Georgia-02C, Georgia-06G, Georgia-07W, Florida-07, Tifguard, Georgia-09B and Georgia-10T, and advanced breeding lines EXP27-1516 and TifGP-2. There were three harvest dates that averaged 132, 146 and 157 days after planting (DAP) across both years and sites. At each harvest date, a minimum of three peanut plants from each plot were separated from the total sample and excess stems and leaves were removed with scissors leaving individual peanut pegs and pods with about 5-cm of stem. Each peanut pod was placed in a “U” shaped metal bracket attached to an electronic force gauge and the stem was pulled manually away from the pod at a steady force until the pod detached. A digging loss (scavenge) machine was used to collect pods remaining in the soil after harvest. Peg strengths were greater at Dawson (6.14 N) compared to Tifton (5.28 N) in 2010 but were similar in 2011 (4.51 and 4.39 N, respectively). Dawson had consistently higher yields (5326 kg/ha) than Tifton (3803 kg/ha) and consistently lower pod loss (562 kg/ha) than Tifton (936 kg/ha). Peanut cultivars with greater peg strength across locations and harvest dates were Georgia-06G, Florida-07, and Georiga-02C. Cultivar Georiga-06G showed the greatest yield across locations and years. Other cultivars may have had stronger peg strength, greater pod yield or lower pod loss but none were more consistent than these three cultivars across years, locations, and harvest dates.