Abstract
Breeding for grain yield (GY) in bread wheat at the International Maize and Wheat Improvement Center (CIMMYT) involves three-stage testing at Obregon, Mexico in different selection environments (SEs). To understand the efficiency of selection in the SEs, we performed a large retrospective quantitative genetics study using CIMMYT’s yield trials evaluated in the SEs (2013–2014 to 2017–2018), the South Asia Bread Wheat Genomic Prediction Yield Trials (SABWGPYTs) evaluated in India, Pakistan, and Bangladesh (2014–2015 to 2017–2018), and the Elite Spring Wheat Yield Trials (ESWYTs) evaluated in several sites globally (2003–2004 to 2016–2017). First, we compared the narrow-sense heritabilities in the Obregon SEs and target sites and observed that the mean heritability in the SEs was 44.2 and 92.3% higher than the mean heritabilities in the SABWGPYT and ESWYT sites, respectively. Second, we observed significant genetic correlations between a SE in Obregon and all the five SABWGPYT sites and 65.1% of the ESWYT sites. Third, we observed high ratios of response to indirect selection in the SEs of Obregon with a mean of 0.80 ± 0.21 and 2.6 ± 5.4 in the SABWGPYT and ESWYT sites, respectively. Furthermore, our results also indicated that for all the SABWGPYT sites and 82% of the ESWYT sites, a response greater than 0.5 can be achieved by indirect selection for GY in Obregon. We also performed genomic prediction for GY in the target sites using the performance of the same lines in the SEs of Obregon and observed moderate mean prediction accuracies of 0.24 ± 0.08 and 0.28 ± 0.08 in the SABWGPYT and ESWYT sites, respectively using the genotype x environment (GxE) model. However, we observed similar accuracies using the baseline model with environment and line effects and no advantage of modeling GxE interactions. Overall, this study provides important insights into the suitability of the Obregon SEs in breeding for GY, while the variable genomic predictabilities of GY and the high year-to-year GY fluctuations reported, highlight the importance of multi-environment testing across time and space to stave off GxE induced uncertainties in varietal yields.
Highlights
Increasing the grain yield (GY) potential of bread wheat (Triticum aestivum L.) and developing resilient varieties are critical to ensure food security amidst the low (0.9%) global average rate of increase (Ray et al, 2013) and escalating challenges like fluctuating temperatures, low precipitation, erratic rainfall patterns, and extreme weather conditions (Wheeler and von Braun, 2013; Curtis and Halford, 2014; Trnka et al, 2014; Tack et al, 2015; Zampieri et al, 2017; Hatfield and Dold, 2018)
Statistical analysis of the GY data (Supplementary Table 4) indicated that in the SABWGPYT sites, the highest mean GY in all the years was observed in India Jabalpur where the mean GY across years ranged between 6.5 and 8.3 t/ha, followed by India Ludhiana (5.4 to 7 t/ha), India Pusa (4.4 to 6.1 t/ha), Pakistan Faisalabad (3.4 to 4.6 t/ha), and Bangladesh Jamalpur (3.1 t/ha)
The mean GY in Pakistan Faisalabad had increased by 36.8% across the two cycles (2015–2016 and 2016–2017)
Summary
Increasing the grain yield (GY) potential of bread wheat (Triticum aestivum L.) and developing resilient varieties are critical to ensure food security amidst the low (0.9%) global average rate of increase (Ray et al, 2013) and escalating challenges like fluctuating temperatures, low precipitation, erratic rainfall patterns, and extreme weather conditions (Wheeler and von Braun, 2013; Curtis and Halford, 2014; Trnka et al, 2014; Tack et al, 2015; Zampieri et al, 2017; Hatfield and Dold, 2018). Borlaug Experimental Research Station, Ciudad Obregon, Sonora, Mexico (27°29′N, 109° 56′W) and analyzes GY data returned by collaborating national partners from its target population of environments (TPEs) to identify lines with temporal and spatial stability over a range of environmental conditions (Crossa et al, 1991; Fox, 1994; Cooper and Byth, 1996; Cooper et al, 1997; Braun et al, 2010) These strategies adopted by CIMMYT have bolstered the development of high-yielding, widely adapted stable wheat lines (Rajaram and Skovmand, 1977; Braun et al, 1996; Singh and Trethowan, 2007; Lage et al, 2008) that have a remarkable impact globally, especially in developing countries (Byerlee and Moya, 1990; Heisey et al, 2002; Lantican et al, 2005; Lantican et al, 2016).
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