California's troubled real estate and construction sectors are likely culprits for state income taxes falling $1.3 billion below projections in January, state Controller John Chiang said Tuesday.

Chiang noted the revenue shortfall at a news conference highlighting changes that will affect state residents as the tax preparation season gets under way.

Last year 15 million individuals and 1 million businesses paid nearly $49 billion in income taxes, the state's largest single source of revenue.

The tax slump, first reported last month by Legislative Analyst Elizabeth Hill, signals potential trouble for Gov. Arnold Schwarzenegger's $103 billion general fund budget recently proposed for a new fiscal year beginning July 1.

The controller's office said the governor's budget proposal may already be $710 million short on revenue.