Abstract
Wheat (Triticum aestivum L.) is a major staple food crop grown worldwide on >220 million ha. Climate change is regarded to have severe effect on wheat yields, and unpredictable drought stress is one of the most important factors. Breeding can significantly contribute to the mitigation of climate change effects on production by developing drought-tolerant wheat germplasm. The objective of our study was to determine the annual genetic gain for grain yield (GY) of the internationally distributed Semi-Arid Wheat Yield Trials, grown during 2002–2003 to 2013–2014 and developed by the Bread Wheat Breeding program at the CIMMYT. We analyzed data from 740 locations across 66 countries, which were classified in low-yielding (LYE) and medium-yielding (MYE) environments according to a cluster analysis. The rate of GY increase (GYC) was estimated relative to four drought-tolerant wheat lines used as constant checks. Our results estimate that the rate of GYC in LYE was 1.8% (38.13 kg ha−1 yr−1), whereas in MYE, it was 1.41% (57.71 kg ha−1 yr−1). The increase in GYC across environments was 1.6% (48.06 kg ha−1 yr−1). The pedigrees of the highest yielding lines through the coefficient of parentage analysis indicated the utilization of three primary sources—‘Pastor’, ‘Baviacora 92’, and synthetic hexaploid derivatives—to develop drought-tolerant, high and stably performing wheat lines. We conclude that CIMMYT’s wheat breeding program continues to deliver adapted germplasm for suboptimal conditions of diverse wheat growing regions worldwide.
Highlights
Wheat (Triticum aestivum L.) is a major staple food crop grown worldwide on >220 million ha
Plants can cope with drought stress in various ways: (i) through an extensive root system to explore higher amounts of soil volume (Anjum et al, 2011), (ii) through osmotic adjustment and the accumulation of solutes such as proline that may improve water uptake (Keyvan, 2010; Anjum et al, 2011), (iii) by maintaining the balance between antioxidants and reactive oxygen species (ROS) levels, which can help to reduce the extent of the oxidative damage due to ROS (Anjum et al, 2011), and (iv) through induced leaf senescence as a survival mechanism to avoid drought and maintain favorable water status, which contributes to nutrient remobilization, allowing the rest of the plant to take advantage of the accumulated nutrients of the senescent leaves (Munné-Bosch and Alegre, 2004)
The first objective of our study was to determine the rate of genetic gain for grain yield (GY) per se in 12 yr of Semi-Arid Wheat Yield Trials grown under suboptimal conditions, with the aid of mixed models and fitting a factor analytical (FA) structure to the variance-covariance matrix of the GE
Summary
Wheat (Triticum aestivum L.) is a major staple food crop grown worldwide on >220 million ha. Breeding can significantly contribute to the mitigation of climate change effects on production by developing drought-tolerant wheat germplasm. The Bread Wheat Breeding Program of the CIMMYT has the objective to breed for 60 million ha in developing countries (i.e., over one-quarter of the global wheat harvested area). To achieve this goal, the concept of the “mega-environment” has been crucial in classifying wheat growing environments according to common environmental features, agronomic practices, and end-use products (Rajaram et al, 1993; White et al, 2001). Frequently only 50% of data is recovered to conduct multilocation analyses
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