# Genetic and Environmental Factors Associated to Glutenin Polymer Characteristics of Wheat
## 3 Results and Discussion
### The Temperature during Grain Maturation Had a Major Influence on Polymers' Characteristics  
Without taking into account the influence of the PC, GH, and glutenin alleles on polymer characteristics, the cumulative daily average temperatures over the month of July were used as unique explanatory variates to explain the polymer characteristics. The best regression, computed to maximize the R\({}^{2}\), was of a linear type for Rw and of an exponential type for Mw and PI. As shown in Figure 2, the cumulative daily average temperatures over the month of July explained 55.1%, 44.8%, and 59.3% (for each, \(n=885\) and \(p<10^{-4}\)) of the phenotypic variations of Rw, Mw, and PI, respectively. These regressions clearly evidence the influence of temperature in the experimental field trial during the last month of the wheat crop, which is highly associated to increasing the polymer characteristics. Other regressions performed using either the average temperature of May or of June or the average temperatures cumulated during the 50 days usually acquired from grain formation to maturity did not explain as much of the polymer characteristics as did the average temperature of the month of July. The vertical dots, corresponding to phenotypic values measured in each location, on Figure 2 result partly from genetic differences between cultivars, which differed for the PC, GH, and glutenin compositions. Nevertheless, as reported in Table 2, a significant part of about 40%, 27%, and 23% of the phenotypic variations of Mw, Rw, and PI, respectively, remain to be explained. The cultivars did not have similar earning precocities, possibly causing different adapted responses to higher temperatures during grain accumulation. In addition, although the A4F-MALLS measurements were replicated, due to a lack of measures on field replicates for all cultivars, the interactions (cultivars \(\times\) locations) were not tested for the 192 cultivars on the 11 locations. Several significant interactions were reported between GH (PinB alleles) and HMW-GS (Glu-A1 alleles or Glu-A3 alleles) for the three polymer characteristics with cultivars grown in 2008-2010 [24]. From a practical approach, when the PC and GH of the grain sample, measured by NIRS, are introduced into the regression, together with the average temperature of the last month of the wheat crop (i.e., July), the above percentages were almost unchanged: 58.4%, 45.0%, and 60.4% for Rw, Mw, and PI, respectively. The highly significant increasing polymer characteristics, associated with different average temperatures from the month of July, were computed from hourly (night and day) daily temperatures recorded in locations where the multilocal trials were implanted: three locations in 2004, two in 2005, three in 2009, and three in 2010. The difference between lowest sum of the daily average temperatures in July (546 \({}^{\circ}\)C) registered at La Chapelle d'Armentiere (North of France) in 2004, and the  
Figure 2: Regressions between the characteristics of the glutenin polymers, measured using Asymmetric Flow Field-Flow Fractionation Multi-Angle Laser Light Scattering (A4F-MALLS), and the cumulative daily mean temperatures (\({}^{\circ}\)C) of July (noted Tmean July) in the 11 wheat trial locations. (**a**) Rw of polymers (nm), **(b**) Mw of polymers (Da), and (**c**) PI of polymers (PI = Mw/Mn). Two locations with similar Tmean values (July, Verneuil I’Etang 2005: 586 \({}^{\circ}\)C and Mons en Pévele 2009: 586.1 \({}^{\circ}\)C) are not separated on the figures. R\({}^{2}\): percentage of phenotypic variance. highest average temperature (656.6 \({}^{\circ}\)C) registered at Clermont Ferrand (Central France) in 2010 was 110.6 \({}^{\circ}\)C. It corresponds to a difference of only 3.5 \({}^{\circ}\)C of the daily average temperature between the two experimental sites (17.6 \({}^{\circ}\)C versus 21.1 \({}^{\circ}\)C). When introduced in the fitted equations (Figure 2), this 3.5 \({}^{\circ}\)C difference caused tremendous changes in the characteristics of the polymers.