Hi Sunil,
This is the current implementation of RadTreeView layout and this behavior can not be changed. We have plans to refactor RadTreeView control and more specifically its layout and data engine. The new version will introduce many improvements regarding themes and possibilities for customizations. You can find more information in our Q1 2011 Roadmap.
Kind regards,
Julian Benkov
the Telerik team
Check out the Q1 2011
Roadmap for Telerik Controls for Windows Forms.