Central to sorghum’s continued success is the development of high-performing hybrids, which blend the best traits of different parent lines to enhance yield and express desirable traits such as insect and disease resistance, drought tolerance, standability and overall quality. A considerable amount of science, time and work goes into making modern day sorghum hybrids. But how exactly are these hybrids made?

A hybrid combines the traits of its two parent lines. These two parent lines consist of a pollen parent (R-line) and a seed parent (A-line). The seed parent is male sterile and does not produce pollen. This allows it to be pollinated by the pollen parent to create the hybrid seed that goes into the commercial seed bag and is planted by the grower.

The lifeline of developing a new commercial hybrid is the creation of elite parent lines with desirable traits. These lines are developed by recombining existing elite parental lines to create new breeding populations or by adding specific traits of interest to existing parental lines by crossing an elite line with a specific donor parent of the desired trait. Once the cross is made it can take up to nine generations with traditional breeding techniques before the new line is ready for commercial hybrid production.

The Hybridization Process

1. Parental Selection: The first step in creating a hybrid is selecting suitable parental lines. Breeders choose lines with complementary traits that they want to combine in the hybrid. For example, one parent might have high yield potential while the other exhibits strong resistance to a particular disease.
2. Crossing: Before the cross can be made, one of the lines must be made male sterile. This is done manually by carefully removing the male reproductive organs (anthers), using a procedure called ‘plastic bag emasculation’, or increasingly by treating with a chemical (TFMSA) that renders the plant male sterile. Pollen from the selected male parent is then transferred to the newly created female parent’s receptive stigma.
3. Seed Development: After successful pollination, the female parent develops seeds that contain genetic material from both parents. These seeds are harvested and planted to grow the hybrid seed.
4. Field Evaluation: The hybrid is then grown in experimental plots to evaluate its performance under different environmental conditions.
5. Selection and Testing: Promising hybrids undergo further testing and selection to ensure their stability and consistency across multiple growing seasons and locations. This rigorous testing phase helps breeders identify hybrids that are well-suited for commercial production.
6. Commercialization: Once a hybrid has proven its performance and stability, parent seed is increased to sufficient quantities to allow for commercial seed production. The parent seed is planted in alternating blocks of the pollen parent and seed parent. Grain from the seed parent is then harvested, processed and ultimately goes into the commercial seed bag that is sold to the grower.

The entire process of making the initial cross to develop a new parent line to commercial production of a new hybrid can take 10 to 12 generations. Fortunately, by using greenhouses and utilizing environments with long growing seasons or located in the southern hemisphere, multiple generations can be accomplished in a single year. New technologies such as doubled haploid can also greatly shorten the number of generations needed to achieve homozygosity of the parent seed.

Computational Breeding

Successful breeding has always been a numbers game with the more crosses that are made between parent lines the greater the odds of finding a successful cross that leads to a new commercial hybrid. However, in recent years advances in technology such as genetic markers and genomic sequencing, and drones that identify desirable plants in the field, provide data that can now be entered into computer programs to select the best candidates for crossing. This greatly increases the odds of breeders making a successful cross that leads to a better hybrid.

Creating sorghum hybrids is a complex yet essential process that combines traditional breeding techniques with cutting-edge technology. By carefully selecting parental lines, cross-pollinating them, and rigorously testing the resulting hybrids, breeders can develop the next generation of hybrids with higher yield, improved resilience and better quality.

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This story originally appeared in the Spring 2024 Issue of Sorghum Grower magazine.