Article Figures & Data
Figures
- Figure 1.
—QTL detected under short and long days in the phytotron at NCSU and in experimental field plantings in Rhode Island and North Carolina. Solid symbols represent QTL detected under SD conditions in the phytotron and SD field conditions experienced by the fall seasonal cohorts. Open symbols represent QTL detected under LD conditions in the phytotron and LD conditions experienced in the field by the spring seasonal cohorts. Lines bracketing the QTL symbols denote the 2-LOD support limits (see Table 4 for exact values). Significance of individual QTL at an experiment-wide error rate of α= 0.05 was determined through permutation tests, with the exception that the QTL with a “+” is significant only at α< 0.15. Multiple symbols with overlapping support limits within an experimental treatment indicate that the LR test statistic dropped below the significance threshold between the two QTL peaks. Colors highlight specific results: pink denotes QTL for bolting date common to all environments; green denotes QTL common to long days in the phytotron and long-day field settings (>12 hrs); blue denotes QTL common to short days in the phytotron and short-day field settings (<12 hrs); gold denotes QTL common to long and short days in the phytotron; and red denotes QTL that significantly affected bolting date only in one or more field environments.
Tables
- TABLE 1
Differences in photoperiod at time of germination and bolting among the seasonal environments and geographic regions
Environment Approximate
date of
germinationDate of first
boltingDays to
first
boltingAverage
days to
boltingShortest photoperiod
between germination
and boltingPhotoperiod
at boltingFall Rhode Island Oct. 17-19 March 1 134 150 9 hr 09 min 11 hr 14 min North Carolina Oct. 31-Nov. 3 December 19 49 73 10 hr 26 min 9 hr 45 min Spring Rhode Island March 21-23 April 28 38 44 12 hr 10 min 13 hr 53 min North Carolina Feb. 22-24 April 15 52 60 11 hr 09 min 13 hr 05 min -
Dates of germination are the dates on which the seed stratification treatments ended and seed trays were placed under ambient photoperiods. Date of first bolting indicates the date the first plants in a cohort began bolting, that is, differentiated a flowering inflorescence, while days to bolting is the absolute number of days elapsed between the time of germination to the time of bolting. The following column provides the average number of days to bolting for a cohort. Because changes in day length may influence bolting date, the shortest photoperiod experienced by a cohort after planting, in addition to the photoperiod on the date of bolting, are presented in the last two columns. Note that the North Carolina fall and Rhode Island spring cohorts experienced day lengths consistently shorter and longer than 12 hr, respectively, from the time of germination to bolting, while the other two cohorts experienced increasing day lengths prior to bolting.
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- TABLE 2
Restricted maximum-likelihood estimates of the among-line variance component, VL, and associated P value within each field and controlled environment
Environment VL Verror P Fall Rhode Island 2.21 13.62 <0.0001 North Carolina 77.40 435.04 <0.0001 Spring Rhode Island 5.31 18.51 <0.0001 North Carolina 5.69 50.21 <0.0001 Long days 2.66 2.77 <0.0001 Short days 11.68 14.70 <0.0001 - TABLE 3
Two-way ANOVA for bolting date responses to seasonal environments in Rhode Island and North Carolina
Source d.f. Mean Variance
squareP Mean Variance
componentA. Rhode Island Line 94 118.30 0.01 1.05 Season 1 1.20 × 106 <0.0001 — Line × season 94 75.29 <0.0001 2.80 Error 4047 18.06 18.04 B. North Carolina Line 94 1527.74 0.05 10.57 Season 1 5.00 × 106 <0.0001 — Line × season 94 1080.54 <0.0001 38.55 Error 3880 250.26 250.59 - TABLE 4
QTL for bolting date under short and long days in the phytotron and in fall and spring seasonal cohorts in Rhode Island and North Carolina
Trait Chromosome QTL map position in
cM (nearest marker)2-LOD
support limit
(cM range)LR Additive
effect/σG[r2] Short days in phytotron 1 49.45 (CATTS039) 41.64-54.66 31.6 -0.12 0.14 2 41.55 (er) 39.24-45.05 31.8 -0.15 0.14 2 79.76 (RRS2) 69.05-79.76 21.9 0.10 0.08 4 58.74 (JGB9) 47.70-69.39 20.6 0.10 0.09 4 69.31 (mi232) 47.70-69.39 19.2 0.09 0.08 5 126.05 (SNP153) 121.54-129.65 34.1 0.17 0.16 Fall cohort in Rhode Island 1 88.81 (agp1e) 82.71-97.71 15.1 -0.14 0.04 1 93.15 (CH.215L) 91.01-96.87 19.7 -0.17 0.06 2 40.89 (er) 39.24-44.05 44.2 -0.28 0.15 3 53.40 (ve021) 47.39-56.90 39.2 0.20 0.12 4 0.01 (mi51) 0.01-3.32 25.1 0.19 0.07 4 56.40 (AG) 53.02-58.74 24.2 0.16 0.08 5 84.01 (mi83) 69.67-90.96 17.4 -0.14 0.04 5 128.15 (CATHHANK) 122.54-132.15 37.9 0.21 0.12 Fall cohort in North Carolina 1 5.40 (apx1A) 0.01-11.17 14.9 -0.04 0.06 1 15.27 (ATTS0477) 11.17-15.57 14.6 -0.04 0.06 1 111.73 (mi103) 111.73-114.24 24.9 0.07 0.16 1 123.82 (ve011) 121.62-127.09 34.1 0.09 0.18 2 60.27 (ve018) 42.05-79.76 14.8 0.04 0.06 2 76.26 (RRS2) 42.05-79.76 14.1 0.04 0.06 4 50.23 (mi260) 43.45-62.10 16.2 0.05 0.07 4 56.90 (AG) 43.45-62.10 14.5 0.05 0.07 5 58.40 (mi291b) 54.91-63.17 23.8 -0.06 0.10 5 127.05 (ve032) 106.45-132.15 10.1 0.03 0.04+ Long days in phytotron 1 0.01 (ve001) 0.01-11.17 14.3 -0.18 0.07 2 16.93 (g4133) 10.20-29.15 18.3 0.20 0.08 2 25.15 (mi398) 10.20-29.15 16.3 0.20 0.07 2 42.55 (er) 36.74-50.05 23.2 -0.25 0.13 5 19.60 (ve033) 16.60-24.42 26.7 0.35 0.15 5 125.05 (SNP153) 120.09-128.15 35.2 0.28 0.19 Spring cohort in Rhode Island 1 0.01 (ve001) 0.01-3.01 32.9 -0.20 0.15 1 111.73 (mi103) 111.73-136.37 15.3 0.14 0.07 1 123.32 (ve011) 119.04-131.37 25.5 0.18 0.10 2 0.05 (ve012) 0.01-12.00 15.2 0.13 0.06 3 61.07 (g4564b) 49.89-71.94 13.9 0.12 0.06 5 14.34 (g3837) 10.01-31.42 18.5 0.15 0.08 5 19.60 (ve033) 9.73-31.27 18.5 0.15 0.08 5 110.99 (emb514) 109.45-132.15 13.8 0.13 0.07 5 125.05 (SNP153) 116.33-128.15 21.3 0.15 0.09 Spring cohort in North Carolina 1 0.01 (ve001) 0.01-11.17 13.6 -0.16 0.07 1 5.40 (apx1A) 0.01-11.17 14.3 -0.16 0.08 1 84.35 (mi209) 79.82-96.37 17.5 -0.19 0.10 1 89.81 (agp1e) 79.82-97.71 14.1 -0.18 0.09 1 126.59 (agp64) 120.04-134.87 20.4 0.21 0.13 4 9.77 (mi301) 6.08-13.34 16.7 -0.22 0.10 5 122.04 (g2368) 114.99-132.15 14.1 0.17 0.08 5 127.55 (CATHHANK) 114.99-132.15 14.1 0.16 0.08 -
QTL for each trait were mapped using composite interval mapping within each geographic region and season. The first three columns indicate the chromosomal location of the QTL, the nearest marker locus, and the centimorgan range defining the 2-LOD support limits around the QTL. The LR is the test statistic for composite interval mapping, the significance of which is determined through permutation analyses (Doerge and Churchill 1996); for all traits, the significance threshold for an experiment-wide error rate of α= 0.05 was <14.2. The “+” symbol denotes a QTL significant at α< 0.15. The second to last column denotes the additive effects. Effects are positive if the Col allele confers bolting later than the Ler allele and negative if the Col allele confers bolting earlier. The final column shows the proportion of variance explained by a QTL, which was calculated as the proportion of the model sums of squares explained by a given QTL in an ANOVA including all significant QTL as main effects.
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