Genetic Improvement in Agronomic Traits of Hard Red Winter Wheat Cultivars 1919 to 1987

Abstract

Periodic evaluation of genetic improvement of crop cultivars is useful, both as a demonstration of the importance of plant breeding to the public and as a way of identifying traits or target environments that may require increased efforts by breeders. Evaluation of cultivars from different eras in a common environment is the most direct of the several methods that have been used to estimate breeding progress. Thirty‐five hard red winter wheat (Triticum aestivum L. em. Thell.) cultivars introduced or released between ca. 1874 and 1987 were evaluated in experiments at three locations in Kansas during 1986 and 1987 (three other cultivars were evaluated only in 1987) to estimate genetic progress achieved by hard red winter wheat breeding programs. Linear regression of cultivar means on years of release showed increases of 16.2 kg ha−1 yr−1 in grain yield, 0.4 kg m−3 yr−1 in volume weight, and 0.04 g yr−1 in thousand‐kernel weight. Days to heading and plant height decreased at rates of −0.1 d yr−1 and −0.5 cm yr−1, respectively. There were also significant increases over time in lodging resistance. There was no significant change in biomass yield over time. Rates of genetic improvement varied significantly across evaluation environments, with the greatest gain in grain yield (1.4% of the experiment mean per year) estimated in an epidemic of stem and leaf rust (caused by Puccinia graminis Pers. f. sp. tritici Eriks. & Henn., and P. recondita Rob. ex. Desm. f. sp. tritici, respectively). Moderate gain per year (0.6%) was estimated in the most highly productive environment, lower gain (0.4%) was found under drought stress, and there was no gain when evaluation was conducted under an epidemic of tan spot (caused by Helminthosporium tritici‐ repentis Died.), a foliar disease. High levels of resistance to H. tritici‐repentis had not been incorporated into hard red winter wheat cultivars. No evidence of a yield plateau was found for hard red winter wheat cultivars evaluated under a range of environmental conditions in Kansas.

Characterization of brazilian wheat cultivars in terms of nitrogen use efficiency

“…These results agree with Rodrigues et al (2007), who found that the genetic gain for GY was more associated with BY than HI in Brazil (r=0.79**). However, this contradicts other studies which point out that the HI is the main responsible for pushing forward the genetic potential of grain yield in wheat (Cox et al, 1988). In the current study there was no significant association between HI and GY (Figure 3b).…”

Breeding Progress for Grain Yield and Yield Related Characters of Kabuli Chickpea (Cicer arietinum L.) in Ethiopia Using Regression Analysis

“…The breeding effect was estimated as a genetic gain for grain yield and associated traits in chickpea improvement by regressing mean of each character for each variety against the year of release of that variety. The magnitude of genetic progress from breeding was estimated by regressing the mean performances of the genotypes on years of varietal release using 1974, when the first variety was released, as the base year (Cox et al, 1988). The linear relationship between a dependent variable Y and independent variable X is represented by the equation:…”

“…The accurate estimation of genetic progress realized from long-term breeding efforts is a difficult task but various procedures may be used. Among the available procedures, the performance of genotypes in common environments regressed over years of varietal release of a given crop as a continuous quantitative variable provided the most direct estimate of genetic gain from breeding and has widely been used in different crops (Cox et al, 1988). For example, genetic progresses using the same procedure were reported in barley (Martintello et al, 1987), groundnut (Mozingo et al, 1987), sunflower (Pereira et al, 1999), wheat (Brancourt-Hulmel et al, 2003;Parveen & Khalil, 2011;Rodrigues et al, 2007;Shearman et al, 2005), soybean (Jin et al, 2010;Liu et al, 2012;Morrison et al, 2000;Ustun et al, 2001) and maize (Luque et al, 2006).…”

Modeling carbon dynamics in vegetation and soil under the impact of soil erosion and deposition

“…The harvest index of winter wheat from 1900 to 1988 increased at a rate of 0.0016 yr À1 (r 2 = 0.68) according to the data of Cox et al [1988]. In this study, we assumed that the historical changes of potential Hi for all crops follow the pattern of winter wheat cultivars as observed by Cox et al [1988].…”

“…The harvest index of winter wheat from 1900 to 1988 increased at a rate of 0.0016 yr À1 (r 2 = 0.68) according to the data of Cox et al [1988]. In this study, we assumed that the historical changes of potential Hi for all crops follow the pattern of winter wheat cultivars as observed by Cox et al [1988]. This assumption was supported by the increase rate of 0.0017 yr À1 observed in corn from 1960 to 1992 [Huggins and Fuchs, 1997], 0.0012 -0.0024 yr À1 for wheat [Austin et al, 1980;Riggs et al, 1981;Wych and Rasmusson, 1983], and others summarized by Hay [1995].…”