The impact of genotype x environment effects on runner type peanut seed vigor response to temperature

Authors: GREY, T - UNIVERSITY OF GEORGIA; BRANCH, W - UNIVERSITY OF GEORGIA; TUBBS, R - UNIVERSITY OF GEORGIA; SNIDER, JOHN - UNIVERSITY OF GEORGIA; WEBSTER, THEODORE; ARNOLD, JASON - PIONEER HI-BRED INTERNATIONAL; XIAO, LI - AUBURN UNIVERSITY

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/8/2016
Publication Date: 7/11/2016
Citation: Grey, T.L., Branch, W.D., Tubbs, R.S., Snider, J.L., Webster, T.M., Arnold, J., Xiao, L. 2016. The impact of genotype x environment effects on runner type peanut seed vigor response to temperature. Agronomy Journal. 108:1424-1433.

Interpretive Summary: United States peanut production from 2007 to 2014 centered mainly in the southern states of Georgia, Alabama, Florida, North Carolina, South Carolina, Virginia, Texas, and Mississippi. The value of peanut to this region has ranged from $0.6 to 1.75 billion over the last eight years. Producers plant different cultivars across this region, but production mainly centers on runner market-type peanut. One unique aspect of runner-type peanut is that almost all cultivars are releases from public institutions from the Southeast region including the University of Georgia, University of Florida,and USDA-ARS, with two additional state breeding programs at Auburn and Clemson Universities recently initiated. New cultivar releases have been a constant factor in grower production as many have improved disease resistance, yield, quality, and value. Planting cultivars with high germination is essential for maximum net return on input costs. Vigor testing can be utilized to evaluate seed for successful field establishment under different environmental conditions. Strong primary seedling development in standard germination testing is regarded as an indicator of strong vigor, but this does not always translate into adequate field performance. One method of testing seed quality, germination, and vigor is the use of a thermal gradient device, allowing for examination single seed lot or multiple seed lots at differing temperatures simultaneously. The objectives of this research were to collect seed from peanut cultivars grown in the same environmental regime each year using the same production practices and then determine if there were genotypic differences. These data indicated that a thermal gradient apparatus successfully evaluated peanut seed of runner-type cultivars for seed vigor, which will assist breeders in determining the success of the cultivar over a range of temperatures, unlike the standard peanut germination test.

Technical Abstract: Experiments were conducted from 2007 to 2012 to evaluate the genotype-by-environment effects on germination and vigor of eight peanut (Arachis hypogaea L.) runner-type cultivars from University of Georgia research trials conducted under the same production practices each year. Irrigated experiments were established in fields with a three year rotation with all other variables (fertility, management, and pesticides) kept consistent each growing season to minimize environmental effects. Peanut seed germination and vigor by plot replication were evaluated in Petri-dishes incubated over a thermal gradient ranging from 14 to 30 C at approximately 1.0 C increments. Peanut seed were counted daily up to 7 consecutive days after initial germination and considered germinated when the radicle was greater than 5 mm long, at which time seed was removed from the dish. Growing degree day (GDD) accumulation for each temperature increment was calculated based on daily mean temperature for that Petri dish as measured by thermocouples. A Lorentzian distribution model was used to establish the temperature and time (hours) to maximum germination. With respect to maximum germination and temperature; Georgia-07W (23.9 C) < Florida-07 (25.0 C) < Georgia Greener (25.2 C) < Georgia-06G (25.3 C) = Tifguard < Georgia Green (26.4) < Georgia-09B (27.1) = Georgia-02C. Non-linear regression indices from logistic growth curves with three parameters were used to elucidate seed germination by cultivar. These data included maximum indices of germination for each cultivar by year, GDD value at 80% germination (Germ80), and temperature required by each cultivar for optimum germination. Peanut cultivar vigor varied by year with respect to overall GDDs to reach 80% germination (Germ80) and maximum germination (b0). Ranking of cultivars by GDD to reach Germ80 were: Georgia Green < Georgia-02C < Georgia-06G = Georgia Greener < Georgia-09B < Georgia-07W < Tifguard < Florida-07. This indicates that Georgia Green, a small seeded cultivar, had much greater vigor than Florida-07, a larger seeded cultivar, over the course of the experiments. Georgia-06G peanut seed were consistent with respect to germination, Germ80, and b0 among the eight evaluated cultivars over the six years of testing. All cultivars exhibited phenotypic variation by year, and genotypic stability across years.