* Court sentences six people to jail for EU farm aid fraud

* Trial outcome crucial to Sofia's progress in fighting graft

SOFIA, June 30 (Reuters) - Six Bulgarians were sentenced to jail on Wednesday for stealing 7.5 million euros ($9.15 million) in European Union farm aid after a trial testing the Balkan country's ability to tackle widespread corruption.

The Sofia City Court sentenced Mario Nikolov and his wife, Mariana Nikolova, to 12 and five years in jail, respectively. Another four people got 10 years in jail.

They were convicted of theft after setting up an organised crime group which forged documents to siphon off millions of euros under the pre-accession farm fund SAPARD.

In March, the Sofia City Court sentenced Nikolov and his wife to 10 and eight years in jail in a separate trial for laundering money from the EU-backed programme. [nLDE62S0SJ]

Both cases are among several high-profile trials seen as an indicator of Sofia's ability to tackle graft.

A failure to show results by July, when Brussels will assess Bulgaria's progress, may threaten access to some of the 11 billion euros promised to the EU's poorest country up to 2013.

In 2008, the European Commission blocked Sofia's access to millions in EU infrastructure and agricultural aid as punishment for the soft approach to fraud of the previous Socialist-led government.

The charges against the six were made after a joint operation by Bulgarian, German and Swiss police in 2007 exposed a criminal network aimed at misusing EU aid.

They have the right to appeal against the verdict.

Three others were also charged, of whom one was given a suspended sentence of three years while two were acquitted.

On Wednesday, the Sofia City Court also ordered the seizure of half the property of the defendants who were found guilty. (Reporting by Irina Ivanova; editing by Myra MacDonald)