Modeling crop breeding for global food security during climate change

Abstract

Simultaneous genetic improvements in grain yield and heat stress tolerance (HST) are necessary to avoid a fall in crop yields caused by global warming during the 21st century. Future food security depends on crop breeding solutions to this challenge, especially in developing countries where the need is greatest. We stochastically model a wheat breeding program during 60 years of rapid global warming based on rapid 2‐year cycles, with selection in early generations for HST, grain yield, disease resistance, and stem strength. In each cycle, breeding values were estimated by best linear unbiased prediction using all pedigree and phenotypic information (including selfing) back to the founders. We compared two methods of selection and mating design with similar costs. The first method was truncation selection for HST to match predicted increases in land temperatures followed by selection for an economic index composed of weighted estimated breeding values for each trait, followed by random pair‐wise mating among selections. The second method was optimal contributions selection (OCS) for the economic index with an overriding constraint to increase HST in each cycle to match global warming trends, and mating prescribed by OCS. Truncation selection caused a rapid loss of genetic diversity, and HST did not keep pace with global warming. Consequently, grain yield began to decline due to heat stress before 60 years. With OCS, HST matched global warming trends, the economic index almost tripled and grain yield nearly doubled during 60 years of global warming. OCS on an economic index, with a priority to meet HST, increased grain yields and avoided a major threat to global food security caused by global warming.

Transient daily heat stress during the early reproductive phase disrupts pod and seed development in Brassica napus L.

“…In this paper and previously (Chen et al., 2019), small but significant genetic variation exists among oilseed rape varieties for tolerance to heat stress. Potentially, screening for heat stress tolerance could be incorporated into oilseed rape breeding programs as part of an optimized breeding strategy for heat stress tolerance, grain yield, disease resistance, and other important agronomic traits (Cowling et al., 2019). We suggest that TC2 (transient daily maximum 32°C, minimum 22°C) would be suitable for large‐scale screening for heat tolerance in canola, because TC2 produced wider variation among genotypes in seed yield and pod formation on the main stem than TC3 (Figure 7).…”

“…Canola seed yield losses of up to 133 kg/ha in Canada (Kutcher et al., 2010) and 300 kg/ha in Australia (Si & Walton, 2004) were expected for every 1°C increase in mean daily postanthesis temperature. Future losses in grain yield due to global warming can be minimized if optimized breeding strategies are employed to simultaneously improve heat stress tolerance, grain yield, disease resistance, and other important agronomic traits (Cowling et al., 2019).…”

Application of multi-trait Bayesian decision theory for parental genomic selection

“…Under the OCT method, the selection of candidates is based on high genetic merit, and on the relationship among the candidates for selection. In general, the main question is how to balance high genetic gains in the next generation while maintaining genetic diversity ( Kinghorn 2011 ; Cowling et al 2019 ). Akdemir and Sánchez (2016) optimized genomic mating between parents under GS by applying a method that uses a function that combines measures of inbreeding as part of the objective function being minimized for a single trait.…”

Gaining Acceptance of Novel Plant Breeding Technologies

“…Crop breeders have been urged to adopt 'multi-objective optimised genomic breeding strategies' to secure future food security [40]. For example, new alleles from gene editing could contribute to heat tolerance in crops, which will be vital for improving grain yield over the next 60 years of global warming [41]. OCS was developed by animal breeders to limit inbreeding depression and minimise genetic drift and loss of potentially valuable alleles [42].…”