Abstract
Wheat (Triticum aestivum L.) is one of the most dominant crops for human and livestock feed. Yields of wheat have declined worldwide due to pathogens and pests. Diuraphis noxia Kurdjomov, Hemiptera, Aphididae (commonly known as Russian wheat aphid, (RWA)) is one of the most devastating aphid pest affecting wheat cultivation in South Africa and other regions. Feeding by this insect causes the appearance of severe symptoms that includes necrosis, streaking and trapping of the heads of the wheat plant. This reduces crop yield and can lead to the death of susceptible cultivars. The use of resistant cultivars against the RWA is being negated by the emergence of resistance breaking biotypes. Previously it was shown that Feeding by the RWA on wheat induces differential expression of microRNA genes. Thus, this study aimed to use next-generation sequencing to identify a larger pool of microRNAs and to further characterise them and their putative targets. In this study, three microRNA libraries (n=12) from Tugela uninfested, Tugela DN uninfested, Tugela infested and Tugela DN infested were constructed respectively. A total of 503 microRNA candidates were obtained of which 42 matched known wheat microRNA. Targets of the identified microRNAs were predicted to include known resistance gene family members and previously identified resistance responses in wheat after infestation by the RWA. The expression of candidate microRNAs and their targets were determined, and displayed differential regulation in both cultivars...
Ph.D. (Botany and Plant Biotechnology)