Date of Graduation

5-2017

Document Type

Thesis

Degree Name

Master of Science in Cell & Molecular Biology (MS)

Degree Level

Graduate

Department

Biological Sciences

Advisor/Mentor

Ainong Shi

Committee Member

John R. Clark

Second Committee Member

Pengyin Chen

Third Committee Member

Vibha Srivastava

Keywords

Association mapping, Cowpea, Salt tolerance

Abstract

Cowpea [Vigna unguiculata (L.) Walp.] (2n=2x=22) is a leguminous crop providing inexpensive protein for human consumption that can be grown worldwide. Salinity is one of the major threats to cowpea production, particularly in semi-arid regions of Africa. Salinity significantly affects seed germination and decreases pod yield in cowpea. However, little has been done to provide farmers salt-tolerant cowpea cultivars. Knowledge on the genetics of cowpea salt tolerance is very limited. This study aimed to:(1) evaluate cowpea salt tolerance at germination stage, (2) evaluate cowpea salt tolerance at seedling stage, (3) conduct an association study for cowpea salt tolerance at germination and seedling stages and to identify SNP markers associated with salt tolerance in cowpea. A total of 151 cowpea genotypes at germination stage and 203 cowpea genotypes at seedling stage were evaluated in this research. Association analysis was performed on 116 genotypes at germination stage and 155 genotypes at seedling stage. The results indicated that: (1) substantial variability in salt tolerance was found among the tested cowpea genotypes at both germination and seedling stages; (2) three SNPs, Scaffold87490_622, Scaffold87490_630, and C35017374_128 were highly associated with salt tolerance at germination stage; (3) seven SNPs Scaffold93827_270, Scaffold68489_600, Scaffold87490_633, Scaffold87490_640, Scaffold82042_3387, C35069468_1916, and Scaffold93942_1089 were found to be associated with salt tolerance at seedling stage, and (4) PI582422, 09-529, PI293584, and PI582570 were highly salt tolerant at germination stage, and PI293570, PI582812, PI582856, PI180014, PI257463, 09-175, 09-529, PI666260, I582402, and PI582340 were highly salt tolerant at seedling stage. This research will have practical applications in cowpea breeding and genetics. The salt tolerant lines could be used as parents for breeding programs and the SNP markers could be used as a tools in cowpea molecular breeding through marker-assisted selection.

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