18-BTT EAGER: A system for the production of haploid inducer lines and cytoplasmic male sterile doubled haploids for efficient hybrid production

Hybrid cultivars are a cornerstone of modern crop production. Seed companies spend many years developing elite inbred parental lines that are used to produce the hybrid seed that farmers plant each season. A major bottleneck in the plant breeding cycle is the need to repeatedly backcross promising parental lines to make them fully inbred. One time-saving solution to this challenge is to use double haploids to directly produce fully inbred lines in one generation. With this approach a haploid plant is first isolated, and then chemical treatment is used to double its chromosomes. The resulting double haploid is by definition fully inbred. For this strategy to be of practical use to plant breeders, a reliable method for producing the initial haploid plants is required. In this proposal our objective is to develop and test a general strategy for making haploid inducer lines that should provide plant breeders with the tool they need to efficiently produce double haploid elite parental lines for hybrid seed production.

Hybrid cultivars are a cornerstone of modern crop production. Seed companies spend many years developing elite inbred parental lines that are used to produce the hybrid seed that farmers plant each season. A major bottleneck in the plant breeding cycle is the need to repeatedly backcross promising parental lines to make them fully inbred. One time-saving solution to this challenge is to use double haploids to directly produce fully inbred lines in one generation. With this approach a haploid plant is first isolated, and then chemical treatment is used to double its chromosomes. The resulting double haploid is by definition fully inbred. For this strategy to be of practical use to plant breeders, a reliable method for producing the initial haploid plants is required. In this proposal our objective is to develop and test a general strategy for making haploid inducer lines that should provide plant breeders with the tool they need to efficiently produce double haploid elite parental lines for hybrid seed production.

Another important component of hybrid seed production is the use of cytoplasmic male sterility. Because seed harvested from a male-sterile plant is guaranteed to be hybrid, using cytoplasmic male sterility in a breeding program makes large scale hybrid seed production practical and cost effective. In order for double haploid technology to be commercially useful for hybrid seed production, it is therefore essential that the strategies for producing double haploids are compatible with cytoplasmic male sterile breeding systems. For this reason, this project will integrate the production of haploid inducer lines within a cytoplasmic male sterile breeding framework in order to maximise the practical benefit and applicability to breeders.

If we are successful, the system that we will establish to create haploid inducer lines for the rapid production of cytoplasmic male sterile double haploids would be broadly applicable to any crop where cytoplasmic male sterility is used to produce hybrid seed, such as alfalfa, beet, canola, carrot, onion, sorghum, sunflower, rice, and the vegetable Brassicas. There is thus considerable potential impact of the outcomes of this project on commercial plant breeding programs in a wide range of economically important crops worldwide. This is particularly important given the issues of Food Security facing many countries, and the need to breed more nutritious and resilient crops. Ultimately our work will benefit consumers by making improved varieties of these crops more rapidly available to the public. This project will provide scientific training and professional development opportunities for postdoctoral associates and students. Because CRISPR/Cas9 gene editing plays a central role in this work, we plan to develop an outreach activity focused on how gene editing can be used to improve vegetable crops. We will present this activity to the general public via established events such as Saturday Science, the Wisconsin Science Festival, and Wisconsin Science Expeditions.