Location: Hard Winter Wheat Genetics Research
Project Number: 3020-21000-012-016-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 1, 2022
End Date: Aug 31, 2025
Objective:
1) Conduct mutational analysis of stripe rust-resistant Amblyopyrum muticum intogression plants for the purpose of cloning the resistance genes.
2) Conduct whole genome sequencing of isolates of Tilletia spp. from wheat for genetic diversity analysis.
3) Conduct field screening of wheat lines for resistance to stripe rust and stem rust.
Approach:
Amblyopyrum muticum is a wild relative of wheat that carries many useful traits. Introgression lines have been created whereby small portions of the genome from A. muticum have been transferred to wheat. We have identified introgression lines with small alien segments that confer resistance, and we plan to clone the resistance genes in those lines. Two thousand seeds of a stripe rust-resistant Amblyopyrum muticum introgression line will be treated with EMS chemical mutagen. Plants will be greenhouse-grown and allowed to self-fertilize after treatment. The second generation will be screened with the stripe rust fungus to identify mutants that are susceptible.
Tilletia tritici and T. laevis are fungi that cause common bunt of wheat. Tilletia controversa is the fungus that causes dwarf bunt of wheat. T. laevis is easy to identify by its smooth spore wall. Distinguishing the other two species morphologically is difficult. We will collect 200 strains of Tilletia species from the Central Plains and compare them to reference isolates of T. tritici, T. controversa, and T. laevis. We will perform whole genome Illumina sequencing using DNA from the haploid phase of each of the ~200 diversity panel isolates. Haploid single-primary sporidium cultures from each isolate will be obtained from germinating teliospores using a micromanipulator. At least 10x coverage of sequencing data will be produced for variant discovery and genotyping using GATK (McKenna et al. 2010).
The experimental approach for stripe rust (also known as yellow rust, YR) is to evaluate germplasm in an inoculated nursery where irrigation is available. Stem rust (SR) field evaluations are conducted at Rocky Ford, KS. Approximate nursery sizes for YR and SR annually are 4000-6000 rows and 1500-2500 rows, respectively. Screening nurseries are planted in incomplete blocks of 80 genotypes containing: 4 to 8 replicated check varieties that are augmented in each block with test genotypes. Replicated check varieties are specific to each disease screening nursery and are used to provide statistical adjustment for spatial variation in disease incidence and severity. For YR, flag leaves will be scored for percent severity and infection type using standard scales. For SR, stems will be scored for percent severity and infection type using standard scales. Field nurseries are planted as 1.2-m rows of each genotype, with 16-row wide sections of the trials planted between highly susceptible spreader genotypes, which are inoculated with pathogen isolates under appropriate environmental conditions. YR spreaders are inoculated with composites of local races of the pathogen. Stem rust nursery spreaders are inoculated with the prevalent North American race of SR, QFCSC.
