sibispp@unisa.ac.za

Triticum aestivum L. is one of the most dominant human and livestock feed crops. Yields of wheat have declined worldwide due to pathogens and pests. Russian wheat aphid is the most devastating aphid pest affecting wheat cultivation in South Africa and other regions. Feeding by this insect causes severe symptoms, including 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 emergence of resistance-breaking biotypes negates the use of resistant cultivars against the RWA. Feeding by the RWA on wheat induces differential expression of microRNA genes. Thus, this study used next-generation sequencing to identify a larger pool of microRNAs and further characterise them and their putative targets.Twelve microRNA libraries from Tugela uninfested, Tugela Dn uninfested, Tugela infested and Tugela Dn infested were constructed respectively. The expression of candidate miRNAs and their targets was determined by quantitative real-time PCR.

The predicted target genes were analysed for their gene ontology placement to determine their biological role in plants. Five hundred three miRNA candidates were obtained; only 87 matched the known Triticum aestivum miRNA. The identified miRNAs seem to target known resistance gene family members and previously identified resistance responses from wheat after infestation by the RWA.

The gene ontology results indicated that most of the identified targets in this study play a role in regulating some biological pathways known to be regulated during wheat-RWA interaction.The use of the next-generation sequencing method has boosted small RNA discoveries at an unprecedented scale.

However, a few of several thousand discovered small RNAs have been functionally characterised. The field of small RNA functional genomics research is still in its early phase, and in the case of complex crops like Triticum aestivum, the progress is even slower. More work needs to be done to characterise more miRNAs. Identifying and characterising more small RNA and their target genes will contribute to our understanding of wheat and RWA interaction.

Once a better understanding of this interaction is achieved, then this knowledge can be utilised in the future production of crops with better resistance against RWA.

Keywords: microRNA, Next-generation sequencing, Russian wheat aphid, Triticum aestivum