General Motors has called time on the giant truck-based SUV after announcing plans to close four factories currently building SUVs and pick-ups, as well as putting the future of Hummer brand in doubt.There was also shock at Ford after its all-conquering F150 pick-up was outsold for the first time in a single month since October 1991. The Toyota Camry, Corolla, Camry and the Honda Civic overtook the erstwhile king of the US showrooms. The news comes on the day that US market sales figures showed that in May, Hummer brand sales fell by 67 per cent, from 4636 units to just 1843. The influence of rocketing fuel prices was underlined by the fact that Mini brand sales were up 47.2 per cent in the same month.GM boss Rick Wagoner said the company would reduce production by some 500,000 units and close four factories by 2010, affecting as many as 10,000 jobs. The plants are at Janesville in Wisconsin, Oshawa in Ontario, Moraine in Ohio and Toluca in Mexico. The Moraine plant builds the Chevy Trailblazer and Saab 9-7x.According to US industry reports, GM's “review” of the Hummer is wide-ranging enough to include increasing the number of Hummer of products, as well as closing it down and “selling it whole or part”. A GM spokeswoman was quoted as saying that GM was probably not making the maximum use of “a great brand” and that it might be better exploited by another company.If Hummer is sold off, one potential buyer might be India's Manhindra & Mahindra, which missed out on buying Jaguar and Land Rover. The firm is known for its concentration on 4x4s, pick-ups and commercial vehicles.