Journal Article

Identification of Molecular Markers Linked to Colour Differentiation and Heat Resistance in Cowpea (Vigna unguiculata L. Warp)

Abstract

Cowpea (Vigna unguiculata) is an important legume crop in the arid regions. Molecular markers linked to colour differentiation and heat resistance in cowpea (Vigna unguiculata L. Walp) varieties were investigated using simple sequence repeat-polymerase chain reaction (SSR-PCR) markers. Ten cowpea varieties (brown and white coloured) obtained from the IITA gene bank in Ibadan were pre-germinated in Petri dishes with sterile water for four days. Genomic DNA was then extracted from the young shoots using the Quick DNA TM plant/seed mini prep kit and procedure. The resulting purified genomic DNA from each variety was split into triplicate (Control, heat-treated at 75°C and 100°C for one hour) to produce 30 genomic DNA samples. SSR-PCR marker assays were carried out on cowpea genomic DNA. Firstly, 8 SSR primers were used for preliminary and discriminate screening of the DNA samples. Two of these primers were found to be polymorphic and reproducible: 6743/7061 for SSR. A phylogenic relationship was established from cluster analysis of optical density and gel photographs using NTSYS-PC and UPGMA. IRRISTAT statistical tool was used to carry out ANOVA analysis of the amplified DNA concentration. SSR primers 6743/7061 produced 25% and 40% polymorphism, respectively. Cluster analysis of the amplified fragments of 30 genomic DNA samples of gel and optical density data reveals overall primers' ability to differentiate colour and heat response among the 10 cowpea varieties. The primers were also effective in differentiating varieties. Cowpeas with brown seed coats were genetically linked to higher heat resistance than white cowpeas.

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