Ab-Ghaffer, Mohamad Bahagia (2012)
Ph.D. thesis, University of Birmingham.
The Brown Plant Hopper (BPH) Nilaparvata lugens (Stal) is the most important phloem feeding insect which can cause a serious problem for world rice production especially in
Asia. Development of novel control strategies can be facilitated firstly by a comparison of BPH feeding behaviour on varieties exhibiting natural genetic variation, and then elucidation of the underlying mechanisms of resistance using molecular information. First, BPH feeding behaviour on 12 rice varieties with varying resistance was investigated using the Electrical
Penetration Graph (EPG) and honeydew clock approaches. Seven feeding behaviours(waveforms) were identified and could be classified into two phases, feeding and nonfeeding.
Cluster analysis separated 12 varieties into 3 main groups, resistant, moderately resistant and susceptible. Gene expression microarray analysis on all the varieties was then
undertaken to identify candidate genes which may contribute to resistance. Insects were not introduced to the rice plant because the research interest was in constitutive rather than inducible genes. The results revealed the difference between resistant and susceptible varieties, and agreed with the EPG and honeydew clock experiment results. Correlation between expression and EPG results, gene ontology (GO) analysis and genetic mapping of known BPH resistance gene markers were conducted to strengthen the candidate genes. Out of 239 genes, a hexose transporter was found in all three analyses and therefore, it was classified as the strongest constitutive candidate gene. The position of this gene is close to QBph10 marker (RM484) on chromosome 10. This gene is involved in the uptake of glucose or fructose and is found expressed in sink organs, indicating that high expression is associated with the increment in nutrient contents. Consequently, it would also increase BPH feeding ability on that plant. There were also several other strong candidate genes identified.
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