1- WHAT IS THE MEANING OF GOVERNMENT BOND?
Government Bond; is a kind of debt security issued by Undersecretariat of Treasury in order to fulfill its more than 1 year debt needs.
With those financial instruments, government guarantees to pay it with its interest yield on the dates specified.
Legal persons can take advantage of government bonds. Furthermore, banks also can keep those bonds in asset item of their financial statements as an investment tool.
Those bonds can be fixed rate, floating rate and exchange rate indexed government bonds.
They are sold with discount sale price like commercial papers.
The difference between discount sale price and nominal price in the date of maturity will be the beneficiary’s income.

2- WHAT IS THE MEANING OF TREASURY BOND?
Those bonds are sold in order to obtain bonds for short term loans of the government in a short span of time.
Its expiry date is maximum 1 year.
The person who has bonds will get interest income after the price is paid to person who has bonds at the end of expiry date specified by the institution (on condition that expiry date of Treasury bond should be less than 1 year).
The person who has bonds will gain principal and interest income at the end of expiry date.
Treasury bond is issued by Undersecretariat of Treasury.
(It was discovered by Walter Bagehot in 1876)

3- ARE INCOMES GAINED THROUGH GOVERNMENT BOND AND TREASURY BOND SUBJECT TO DECLARATION?
NO.
State-run government bonds and treasury bonds (exported) are not subject to declaration regardless of the amount of their interest income gained in 2016. 

They will not be subject to declaration even if a declaration is submitted because of other incomes.

Furthermore, incomes gained through sale and purchase of government bonds and treasury bonds in 2016 will not be subject to declaration regardless of their amounts like interest incomes.

In the event of a declaration because of other incomes, they will not be included in declaration. Tax cut (stoppage), which is done through sale-purchase and interest income by the bank, will be the final tax.

Source: Revenue Administration