Gene silencing in bread wheat (Triticum aestivum L.) following a biolistics approach
Thesis (MSc)--Stellenbosch University, 2014.
ENGLISH ABSTRACT: Global food security is hampered by a variety of insects/pest and plant diseases. In wheat, the Russian wheat aphid (RWA) is a significant pest problem in many areas of the world. Wheat has developed defensive mechanisms against the RWA over time which are activated upon feeding. One such mechanism is the hypersensitive response (HR) which is effective against phloem-feeding insects i.e. D. noxia (Diuraphis noxia, Kurdjumov, RWA). In this study, two genes associated with the hypersensitive response i.e. ascorbate peroxidase (APX) and glutathione S transferase (GSTF6b) were investigated to elucidate their function in the defensive mechanism of wheat using a reverse genetic approach i.e. particle bombardment. This study has succeeded in the established of a tissue culture and transformation system which generated three genetically modified wheat plants with decreased resistance to RWA feeding due to gene silencing. The establishment of this system enabled to test the association of defensive related genes in wheat to RWA resistance. Expression analysis performed on obtained transgenics before and after RWA infestation reavealed that the silenced plants were more susceptible to RWA feeding. Chlorosis was observed in the Gamtoos-S-APX transgenic plant which is an indicator of oxidative damage to the photosynthetic machinery of the plant. Decreased GSTF6b transcripts was found in the transgenic Gamtoos-S-GSTF6b and transgenic Gamtoos-R-GSTF6b transgenic plants but no visible symptoms of infestation was observed in these two plants. Resistance breeding could be strengthened by developing broad spectrum resistance plants by incorporating wheat defensive related genes with known function into the breeding programs. The use of this transformation system will allow rapid identification and introduction of agronomically important genes by upregulating these genes to enhance bread wheat against aphid infestation.