Rapid breeding and varietal replacement are critical to adaptation of cropping systems in the developing world to climate change

Gary N Atlin,Jill E Cairns,Biswanath Das

doi:10.1016/j.gfs.2017.01.008

Abstract

Plant breeding is a key mechanism for adaptation of cropping systems to climate change. Much discussion of breeding for climate change focuses on genes with large effects on heat and drought tolerance, but phenology and stress tolerance are highly polygenic. Adaptation will therefore mainly result from continually adjusting allele frequencies at many loci through rapid-cycle breeding that delivers a steady stream of incrementally improved cultivars. This will require access to elite germplasm from other regions, shortened breeding cycles, and multi-location testing systems that adequately sample the target population of environments. The objective of breeding and seed systems serving smallholder farmers should be to ensure that they use varieties developed in the last 10 years. Rapid varietal turnover must be supported by active dissemination of new varieties, and active withdrawal of obsolete ones. Commercial seed systems in temperate regions achieve this through competitive seed markets, but in the developing world, most crops are not served by competitive commercial seed systems, and many varieties date from the end of the Green Revolution (the late 1970s, when the second generation of modern rice and wheat varieties had been widely adopted). These obsolete varieties were developed in a climate different than today's, placing farmers at risk. To reduce this risk, a strengthened breeding system is needed, with freer international exchange of elite varieties, short breeding cycles, high selection intensity, wide-scale phenotyping, and accurate selection supported by genomic technology. Governments need to incentivize varietal release and dissemination systems to continuously replace obsolete varieties.

Highlights

Plant breeding is a key mechanism for adaptation of cropping systems to climate change
Even if breeding programs obtain heat- and drought-tolerant parents, aggressively accelerate breeding cycles, and test materials under the full range of environments likely to occur in the future within their target population of environments (TPE), they will not contribute to climate change adaptation if varieties are not continuously replaced in farmers’ fields
We have argued here that climate change adaptation in crop production can be delivered by rapid-cycle breeding programs that generate a steadily improving stream of varieties

Summary

Elements of climate-adaptive breeding and seed systems

CGIAR gene banks, as well as those of the USDA, still freely provide breeding programs with access to the great diversity in their collections (Heisey and Day Rubenstein, 2015; Galluzi et al, 2015) These collections consist mainly of unimproved landraces, which are important sources of alleles for stress tolerance and disease resistance but are usually narrowly adapted to their environment of origin, and are unsuitable for modern commercial agriculture because they lack the fertilizer responsiveness and yield potential farmers need now. The preservation and expansion of the CGIAR's global breeding networks is critical to the developing world's capacity to adapt to climate change These networks, which often test varieties in a broad range of environments and regions, generating materials with a broad range of adaptation, are often the only accessible sources of elite germplasm from other countries for small breeding programs. They are critical to climate change adaptation in the developing world

The importance of rapid breeding cycles

The need for seed systems that rapidly replace varieties

Findings

Conclusions