Assessing parental donation effects on the baking quality of hybrid wheat to improve breeding efforts

Milson, James Alexander ORCID: 0000-0002-5155-6266 (2025). Assessing parental donation effects on the baking quality of hybrid wheat to improve breeding efforts. University of Birmingham. Ph.D.

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Abstract

Molecular advances now mean that a system-based production of F1 hybrid wheat seed is imminent. Like maize, rice, and barley, hybrid wheat could benefit from increased yield, disease resistance, and improved growth. This is largely due to the phenomenon of heterosis, where hybrids outperform their parental varieties. Unlike other hybridised crops, we need to understand the baking quality of hybrid wheat. The goal is to produce high baking quality hybrid wheat varieties while also having the benefits seen in the other crops.

Baking quality is known to be influenced by multiple loci, each with multiple possible alleles with varying effects. While these alleles are well studied in inbred lines, which are homozygous, the interactions within hybrids, especially when in heterozygous states, is not well understood. We therefore investigated the influence of parental quality genotype on the baking quality within a hybrid breeding population, aiming to understand how different parental genotypes of 17 possible alleles contribute to the baking quality of hybrid wheat. Across three years of field trials using the 227 hybrid crosses produced for the bread-making market in France, we found that the Hagberg falling number phenotype depended on the maternal donations of the Glu-1 loci whereas the hardness index depended on the paternal donations. Although reciprocal quality genotypes were present in the hybrid breeding population, varieties were only used as either a male or female in the field based F1 production.

To further test the effect of different parental genotypes, we created a population of reciprocal hybrids that differed by one or a few quality alleles. This preliminary study, based on one year of field data, showed a greater number of parent-of-origin effects on baking quality phenotypes than had been observed in the breeding population. Parent-of-origin effects were often attributed to the differential expression of parental alleles. To determine whether this was the cause of the phenotypes observed, we measured the relative expression of Glu-B1 in the reciprocal hybrids. We conducted the test at the time point of highest expression, 30 days after pollination, and found no differences in the expression of these alleles. Therefore, the parentof-origin effects observed on the quality phenotype were not due to differences in allele expression in 30-day-old seeds.

To further our understanding of parental effects in hybrid wheat grains, we identified imprinted genes in the leaf-early and mature-stage endosperm of Paragon × Cadenza and Paragon × Chinese Spring F1s and their reciprocal F1s. In total, we identified 126 genes that were imprinted in the endosperm. Genes imprinted across both time points or crosses were hypothesised to have imprinting maintenance essential for their function. We identified three maternally imprinted endosperm genes at all time points and in both crosses, meaning that the maternally donated gene was expressed while the paternal gene was largely silenced. While these genes did not yet have annotated functions, they presented interesting avenues for further research. We also identified 19 transcription factors that were imprinted in the F1
endosperm of wheat, suggesting that further gene networks were also under the control of one of the parental genomes. Among these imprinted transcription factors, four maternally imprinted NAC transcription factors had homologs known to regulate starch and seed storage
protein synthesis in rice and maize. This suggested that part of the control of these pathways was maternally regulated; however, these transcription factors needed to be functionally characterised in wheat to confirm this.

In summary, the work described in thesis demonstrated that certain quality traits could be influenced by parental contributions, indicating that wheat hybrid breeding programs need to design crosses to incorporate specific alleles from a particular parent. However, not all beneficial alleles require this approach, and further research will be required to confirm these findings and determine their specificity to the quality market or broader breeding efforts. While parent-of-origin effects were not linked to differential allele expression, a broader analysis of gene expression identified several genes that were imprinted in developing endosperm and could potentially influence quality traits.

Type of Work:	Thesis (Doctorates > Ph.D.)
Award Type:	Doctorates > Ph.D.
Supervisor(s):	Supervisor(s) Email ORCID Catoni, Marco UNSPECIFIED orcid.org/0000-0002-3258-2522 Borrill, Philippa UNSPECIFIED orcid.org/0000-0002-7623-8256 Bird, Nicholas UNSPECIFIED orcid.org/0000-0002-2476-9020
Licence:	All rights reserved
College/Faculty:	Colleges > College of Life & Environmental Sciences
School or Department:	School of Biosciences
Funders:	Biotechnology and Biological Sciences Research Council
Subjects:	Q Science > QK Botany S Agriculture > S Agriculture (General)
URI:	http://etheses.bham.ac.uk/id/eprint/16035

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