Email: Velu@cgiar.org

Accelerating the rate of genetic gain for grain yield, grain Zn together with key agronomic traits is pivotal for delivering improved wheat varieties. Great progress has been made in the past decade in transferring alleles for high-zinc (Zn) and iron (Fe) from diverse genetic resources into elite wheat breeding lines. However, the major challenge is to maintain simultaneous and high rates of genetic gains for grain yield and grain Zn to meet the food and nutritional security demands through the continuous delivery of biofortified varieties that are competitive to replace non-biofortified varieties successfully.

Although a few intermediate effect QTL regions are identified for grain Zn, both yield and Zn content are quantitatively inherited. Increased breeding efforts and new approaches are therefore required to combine them in high frequency in CIMMYT’s elite germplasm, ensuring that Zn levels are steadily increased to the required levels across the CIMMYT breeding pipelines. The addition of Zn as a core-trait will be achieved through significant acceleration in the breeding cycle, expanding population sizes, extensive Zn phenotyping, yield testing, phenotyping for biotic and abiotic stresses, molecular-assisted selection and genomic selection.

While continuing to increase agronomic performance, high Zn alleles has been added as a core-trait. Eventually Zn content will be increased in the elite lines annually along with the frequency of elite lines with high yield and other agronomic traits that have potential to be released by partners. A genomics assisted “rapid cycle recurrent selection” scheme achieved through rapid generation advancement approaches are being used in the CIMMYT wheat breeding program to mainstream grain Zn in the majority of elite lines.

Early-generation advancement using the speed breeding scheme that reduces operational costs and reduce time to recycle new parents; making advancement decisions for elite lines using data from intensive multi-trait, multi-year and multi-environment phenotyping; selection indices based parental selection and reycling and maintaining effective partnerships with the National Agricultural Research Systems for testing, releasing, and disseminating varieties to farmers.

Following activities implemented in the CIMMYT’s spring wheat breeding program to accelerate rate of genetic gain.

Faster recycling approaches: The 3-yr breeding cycle uses a rapid bulk generation advancement (RBGA) scheme fully optimized; The accelerated generation advancement coupled with field selections will shorten the breeding cycle from 6.25 to 3.65 years (saving 40% time).

Improved selection accuracy and increased selection intensity: We optimized the selection strategy to identify parental lines combining high yield, disease resistance and high Zn by increasing selection intensity.

Optimized the testing strategy for stage 1 and stage 2 lines. All stage 1 lines are phenotyped across 4 selection environments in Obregon, and the promising high yielding, high Zn lines are recycled after stage 1 while the best lines are advanced to stage 2 testing.

Centralized trait augmentation pipeline: the centralized speed breeding trait-augmentation approach introgressed some key resistance genes for stem rust, yellow rust, wheat blast and spot blotch into elite backgrounds.

Zn mainstreaming: Mainstreaming of grain Zn in elite lines was accelerated and about 60% of current crossing block parents possess high Zn; new crosses were made using parents with high breeding value for grain yield, high Zn and other agronomically important traits.