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OLUWOLE, OLUBUSAYO OLAYEMI and Covenant University, Theses (2023) SEED LONGEVITY EVALUATION AND GENOME-WIDE ASSOCIATION STUDIES ON SOME NUTRITIONAL TRAITS OF AFRICAN YAM BEAN. ["eprint_fieldopt_thesis_type_phd" not defined] thesis, Covenant University.

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African yam bean (AYB) (Sphenostylis stenocarpa Hochst. Ex A. Rich) is a neglected legume that has potential to contribute towards alleviating food insecurity in sub-Saharan Africa. As an underutilised legume, AYB provides a great source of protein and starch, with low oil content. Seed nutritional content is a quantitative trait influenced by environmental effects, genes and an interaction of both. These seed nutritional contents (e.g. oil content) are known to influence seed longevity. Seed longevity is the period of time a seed remains viable during storage. Understanding the genetic basis of nutritional traits will contribute to adequate plant conservation as well as food and nutrition security. The aim of this research was to identify the candidate genes associated with AYB seed oil content, seed protein content and the seed starch content, and also assess the influence of these traits on seed longevity of African yam bean. A total of one hundred and thirty-four accessions of African yam bean were used for this research. The nutritional traits i.e., the seed oil, protein and starch contents were analysed using the Soxtec, Kjeltec and Phenol-sulphuric acid method, respectively. Twelve AYB accessions were selected from the one hundred and thirty-four accessions on the basis of high and low protein and oil content for the seed longevity evaluation. The seeds were planted and at harvest maturity, the seeds were harvested, divided into five seed lots and dried at two different temperatures (17 ℃ (control) and 45 ℃). In this study, variation was observed in the seed lots subjected to initial high-temperature drying (45 ℃) and their subsequent seed longevity. Ten out of twelve accessions, which were subjected to two-stage drying at 45 ℃ and 17 ℃ showed better seed longevity when compared to seeds dried at only 17 ℃ in the drying room. A significant positive association was observed between the seed longevity (p50) of seeds across all the treatments indicating that seed starch content has a role to play in AYB seed longevity. A genome-wide association study (GWAS) was also carried out on some nutritional traits (i.e., seed oil, seed protein and seed starch content) collected from two planting seasons (2018/2019 and 2019/2020) for one hundred and thirty-four accessions of African yam bean based on 2,485 SNP (single nucleotide polymorphism) markers. A total of five, six, and two SNP markers were found to be significantly associated with genes responsible for oil, protein and starch content, respectively. Also, one pleotropic marker 100004767|F|0-39:A>T-39:A>T was observed to be associated with both AYB seed oil and protein content. This study identified the candidate genes that may be responsible for AYB seed oil, protein and starch content and this can expedite the molecular breeding process using marker-assisted selection. Also, the two-stage temperature drying revealed the importance of adequate seed drying for optimum ex situ conservation of seeds. The effect of high temperature drying (45 ℃) on the seed longevity of AYB provided a more efficient protocol to be used in conserving genetic resources, which indirectly contribute to food security.

Item Type: Thesis (["eprint_fieldopt_thesis_type_phd" not defined])
Uncontrolled Keywords: African yam bean, Genome-wide Association Studies, Seed longevity, Seed oil content, Seed protein content, Seed starch content, Sphenostylis stenocarpa.
Subjects: Q Science > Q Science (General)
Q Science > QH Natural history > QH301 Biology
Divisions: Faculty of Medicine, Health and Life Sciences > School of Biological Sciences
Depositing User: AKINWUMI
Date Deposited: 04 Aug 2023 14:11
Last Modified: 04 Aug 2023 14:11

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