**5. Research**

There were differences for environmental measures taken during the course of each experiment. All experiments were conducted at times when runner-type peanut seed production could normally occur and are thus representative of producer practices. Cumulative rainfall ranged from 555 to 841 mm between the times of the first and last planting (**Table 1**), which are representative for the region. Irrigation was applied as recommended when required (data not shown). Maximum solar radiation (MJ m−2) and total GDD occurred each year with the May, as opposed to April or June, planting dates for all three site-year locations. Significant cultivar-byyear interactions prevented the data from being combined by cultivar across tests. Therefore, data for the Dawson 2008 and 2009, and Headland 2009 seed experiments were analyzed separately and presented by seed location and planting date for each cultivar (**Table 1**).

There are three primary requirements for seed germination: heat, water, and oxygen. Temperature was the only variable evaluated for the runner-type peanut seed in this research. It is an important factor influencing germination in the field [48, 50]. Germination patterns by day against temperature under thermal times were consistent from year to year (Data not shown). Patterns were nonlinear in progression with germination beginning slowly at low temperatures, followed by a rapid growth phase from 20 to 32°C and then remained constant. The optimum temperatures for experiments were >25°C for all intervals greater than 48 hours. Variation in radicle development occurred with respect to temperature, and therefore variation in vigor detected (**Figure 4**).

**Figure 4.** Runner-type peanut seed radicle length 144hours after initiation for temperatures of 18, 22, 26 and 30°C.Photograph curiosity of Sidney Cromer.

Germination varied by year and planting date for each experiment. For Dawson 2008 runner-type peanut seed germination was 79–93% across all planting dates and cultivars when averaged over all temperatures (**Table 2**). While these differences are noted, they do not relate to seed vigor. For non-linear regression, the seed produced from all cultivars had a greater germination rate (parameter *a*) of 89–93% for the 12 May 2008 planting date, as opposed to the 21 April or 1 June plantings at 79–86%. Using 95% confidence intervals, the three parameters in the logistics growth curves were compared within cultivars over planting dates [51]. Maximum germination rate (parameter *a*) were different dependent on the cultivar and time of planting (**Table 2**). Overall runner-type peanut seed produced from 21 April, 12 May, and 2 June 2008 plantings maintained a high level of vigor when exposed to gradient temperatures ranging from 14 to 35°C. Overlap existed in parameters *b*1 and *b*2 in most cultivars, indicating that the initial germination rate and growth speed were similar (**Figure 5**), although some significant differences did occur (**Table 2**). Runner-type

**5. Research**

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curiosity of Sidney Cromer.

There were differences for environmental measures taken during the course of each experiment. All experiments were conducted at times when runner-type peanut seed production could normally occur and are thus representative of producer practices. Cumulative rainfall ranged from 555 to 841 mm between the times of the first and last planting (**Table 1**), which are representative for the region. Irrigation was applied as recommended when required (data not shown). Maximum solar radiation (MJ m−2) and total GDD occurred each year with the May, as opposed to April or June, planting dates for all three site-year locations. Significant cultivar-byyear interactions prevented the data from being combined by cultivar across tests. Therefore, data for the Dawson 2008 and 2009, and Headland 2009 seed experiments were analyzed sepa-

There are three primary requirements for seed germination: heat, water, and oxygen. Temperature was the only variable evaluated for the runner-type peanut seed in this research. It is an important factor influencing germination in the field [48, 50]. Germination patterns by day against temperature under thermal times were consistent from year to year (Data not shown). Patterns were nonlinear in progression with germination beginning slowly at low temperatures, followed by a rapid growth phase from 20 to 32°C and then remained constant. The optimum temperatures for experiments were >25°C for all intervals greater than 48 hours. Variation in radicle development occurred with respect to temperature, and therefore variation in vigor detected (**Figure 4**).

**Figure 4.** Runner-type peanut seed radicle length 144hours after initiation for temperatures of 18, 22, 26 and 30°C.Photograph

rately and presented by seed location and planting date for each cultivar (**Table 1**).


a Year seed were grown, tested the following year after processing; n = 1920 seed.

b CL, confidence limit; Germ80, cumulative growing degree day value at 80% germination; NA, not applicable as the seed lot of that cultivar did not achieve 80% germination over the duration of the assay; GDD, growing degree day.

c Parameter estimates calculated by nonlinear regression equation (2) for seed germination with respect to time based on GDD accumulation: *a* is the height of the horizontal asymptote at a very large X, *b1* is expected value of Y (cumulative germination) at time X = 0, and *b2* is a measure of growth rate.

<sup>d</sup>Values for each parameter within a column for each cultivar followed by the same letter are not significantly different at the 5% probability level. General linear models procedures were used with mean separation using 95% asymptotic confidence intervals. To obtain the equation for the respective regression line in **Figure 1**, the parameters from this table are used.

**Table 2.** Standard germinationa , logistic growth parameter estimates, 95% confidence limits (CL<sup>b</sup> ), and vigor indices (Germ80 b ) for germination of seed lots of runner-type peanut planted over 40-day period in 2008<sup>a</sup> at Dawson Georgia using a thermogradient germination assay.

peanut seed produced for all planting dates and cultivars in 2008 Dawson Germ80 were 22–40 GDD. This was similar to other research comparing runner-type breeder seed over a 6-year period with Germ80s of 24–42 GDD [37].

Data from 2009 varied by location, planting date, and cultivar. Germination was 59–75% for runner-type seed produced at Dawson (**Table 3**). Runner-type peanut seed produced from the Dawson 11 May 2009 plantings had the most consistent maximum germination rates

**Figure 5.** Cumulative germination patterns for runner-type peanut seed produced in 2008 at Dawson Georgia, based on nonlinear regression using growing-degree day (GDD) accumulation with a base temperature 15°C. To calculate the regression equation for the respective seed lot, the parameter estimates shown in **Table 2** for the Eq. (2) were used. Germination was measured on a thermal gradient.


peanut seed produced for all planting dates and cultivars in 2008 Dawson Germ80 were 22–40 GDD. This was similar to other research comparing runner-type breeder seed over a

Data from 2009 varied by location, planting date, and cultivar. Germination was 59–75% for runner-type seed produced at Dawson (**Table 3**). Runner-type peanut seed produced from the Dawson 11 May 2009 plantings had the most consistent maximum germination rates

> **Georgia-03L 2008 Dawson**

> > **FR458 2008 Dawson**

**Growing-degree days**

**20 40 60 80 100**

**Georgia Green 2008 Dawson** 

> **21 April 12 May 2 June**

**AT3085RO 2008 Dawson**

**AT271516 2008 Dawson**

**Figure 5.** Cumulative germination patterns for runner-type peanut seed produced in 2008 at Dawson Georgia, based on nonlinear regression using growing-degree day (GDD) accumulation with a base temperature 15°C. To calculate the regression equation for the respective seed lot, the parameter estimates shown in **Table 2** for the Eq. (2) were used.

**Growing-Degree Days 0 02 0 40 6 80 100**

Germination was measured on a thermal gradient.

6-year period with Germ80s of 24–42 GDD [37].

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(parameter *a*) of 79.8–93.6%, as compared to 21 April at 54.3–72.8%, and 1 June at 57.3–97.1% (**Table 3**). Vigor differences were noted as none of the seed produced from 21 April plantings achieved 80% maximum rate of germination. Similarly, all seed produced from 1 June planting at Dawson in 2009, except GA-03 L at 97.1%, had low vigor as determined by maximum rate of germination (**Figure 6**). The Germ80 for Dawson 2009 seed were 25–40 GDD for the 11 May

**Figure 6.** Cumulative germination patterns for runner-type peanut seed produced in 2009 at Dawson Georgia, based on nonlinear regression using growing-degree day (GDD) accumulation with a base temperature 15°C. To calculate the regression equation for the respective seed lot, the parameter estimates shown in **Table 3** for the Eq. (2) were used. Germination was measured on a thermal gradient.


Characterization of Genotype by Planting Date Effects on Runner-Type Peanut Seed Germination... http://dx.doi.org/10.5772/intechopen.70584

(parameter *a*) of 79.8–93.6%, as compared to 21 April at 54.3–72.8%, and 1 June at 57.3–97.1% (**Table 3**). Vigor differences were noted as none of the seed produced from 21 April plantings achieved 80% maximum rate of germination. Similarly, all seed produced from 1 June planting at Dawson in 2009, except GA-03 L at 97.1%, had low vigor as determined by maximum rate of germination (**Figure 6**). The Germ80 for Dawson 2009 seed were 25–40 GDD for the 11 May

> **Georgia Green 2009 Dawson**

> > **21 April 11 May 1 June**

**GA-03L 2009 Dawson**

> **FR458 2009 Dawson**

**40 Growing-Degree Days**

**20 60 80**

**AT3085O 2009 Dawson**

**AT271516 2009 Dawson**

**Figure 6.** Cumulative germination patterns for runner-type peanut seed produced in 2009 at Dawson Georgia, based on nonlinear regression using growing-degree day (GDD) accumulation with a base temperature 15°C. To calculate the regression equation for the respective seed lot, the parameter estimates shown in **Table 3** for the Eq. (2) were used.

**40 Growing-degree days 0 02 60 80**

Germination was measured on a thermal gradient.

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plantings, however, seed from the 21 April plantings had poor vigor and never achieved Germ80, while only GA-03 L had a Germ80 of 35 GDD for seed from the 1 June planting date.

Runner-type seed produced by any planting date for Headland 2009 had very poor germination and vigor. Germination was less than 70% (**Table 4**). The maximum rate of germination (parameter *a*) for vigor was less than 75.6% for all cultivars and planting dates. Germ80 was not achieved indicating low vigor (**Figure 7**). Previous research has indicated that there can

**Figure 7.** Cumulative germination patterns for runner-type peanut seed produced in 2009 at Headland Alablama, based on nonlinear regression using growing-degree day (GDD) accumulation with a base temperature 15°C. To calculate the regression equation for the respective seed lot, the parameter estimates shown in **Table 4** for the Eq. (2) were used. Germination was measured on a thermal gradient.

be variability of vigor for runner-type peanut seed of unknown origin, especially when the environmental condition under which that seed is produced is unknown [22].
