Developing systems to control male fertility in wheat for hybrid breeding, enhanced pollen production and increased yield

The challenge

Control of fertility and successful reproduction is key to grain set and, thus, crop yield in cereals. Self-pollinating crops tend to have lower yield capability than hybrids (generated by intercrossing between elite lines). This "Hybrid Vigour" has been shown to increase yield but also abiotic and biotic stress resistance. Hybrid crops, thus, provide opportunities to increase yield and productivity in a sustainable manner. The challenge for hybrid production, however, is the need to avoid the natural tendency for many crops to self-fertilise prior to outcrossing, while ensuring effective cross-pollination for hybrid seed production. Mechanisms that control fertility in a reversible manner are critical to deliver such systems and this is a key goal for wheat breeding.

The project

This project will develop systems to control cereal fertility. It will focus on wheat but also use barley as a further characterisation system. 

The main objectives of the project are: 

1. Development and evaluation of systems for inducible control of hybrid development.

To develop systems to control male fertility for hybrid breeding in wheat, by capitalising upon knowledge from our environmental switchable systems for controlling male fertility in barley. These systems will be tested for their ability to control fertility stably under different environmental conditions for breeding and hybrid production. 

2. To identify traits for enhanced pollen production and resilience of pollen viability. 

Diverse germplasm, including wheat TILLING populations and Introgression lines from the Nottingham Wheat Improvement Centre, will be screened for traits for optimal male fertility, to maximise fertility in male breeding lines. These will include increased anther size, enhanced pollen release and viability, with particular focus towards resilience to abiotic stress.

3. Evaluation of traits for optimal reproduction and hybrid development.

Traits for breeding and hybrid development will be transferred into elite germplasm to evaluate the impact on fertility control and the effect on yield of outcrossing as compared with inbred materials.

4. To assess allelic diversity and generate markers at key loci for pollen development.

Allelic diversity at key loci will be used to provide understanding of the traits for crop fertility. Markers will be developed for these loci to enable germplasm to be tracked during breeding schemes. This will allow traits linked to enhanced fertility or for those that could potentially lead to reduced fertility particularly under variable environments to be identified in breeding schemes. 

Hybrid seed production also relies upon effective males to pollinate the female lines, therefore traits for optimal pollen production, viability and release are also of major importance. Wheat pollen development is particularly sensitive to environmental damage, with rapid reductions in viability post anthesis, combined with general sensitivity to abiotic stress (e.g. high and low temperature) during development. Reductions in fertility due to environmental stress are often seen in wheat crops and these can have major impacts on yield. Reproductive resilience to variable environmental conditions and abiotic stress is, therefore, critical to sustainable yields. This can only be delivered by detailed knowledge of pollen development and systems that regulate fertility. 

The benefits

This work will provide a greater understanding of pollen development in cereals towards establishing switchable systems for the control of wheat fertility but also by identifying traits for enhanced pollen production and viability, particularly under environmental stress, which are critical for ensuring successful pollination in breeding programmes. By investigating the mechanisms behind these traits and by generating tools for breeding and selection, effective breeding to increase crop productivity and resilience will be realised.

Also..

Increased expression of the MALE STERILITY1 transcription factor gene results in temperature-sensitive male sterility in barley

José Fernández-Gómez, Behzad Talle, Zoe A Wilson (2020) J Exp Bot. 71: 6328-39