TORONTO (Reuters) - BlackBerry Ltd (>> BlackBerry Ltd) shares fell as much as 3.6 percent on the Toronto Stock Exchange on Tuesday after brokerage Goldman Sachs issued a "sell" recommendation on the stock, citing concerns about rising competition in its mobile software business.

Goldman analyst Gabriela Borges said she expects BlackBerry's software for managing mobile devices will face increased competition as larger rivals including Citrix Systems Inc (>> Citrix Systems), Microsoft Corp (>> Microsoft Corporation) and VMWare Inc (>> VMware, Inc.) bundle those products into broader business software offerings.

The "sell" recommendation follows a disappointing quarterly earnings report from BlackBerry in late June. Its shares have tumbled by a third since an early June peak amid concern the company will not be able to meet frothy expectations for sales of fledgling new products, including automotive software.

Tim Ghriskey, who helps manage $1.5 billion as chief investment officer with Solaris Asset Management, said it will be difficult for BlackBerry to become a dominant player in the fast-growing market for autonomous-vehicle software.

"There are so many ways that the story could evolve," said Ghriskey, whose firm does not hold BlackBerry shares.

In a note to investors, Borges cautioned that expansion into self-driving vehicles is unlikely to bear fruit in the next 18 months, given long production cycles in the auto industry and intense investment by rivals in the self-driving car market.

While BlackBerry products to secure computer systems on automobiles look promising and could address a market worth $1.1 billion by 2020, she said it is too early to say how much it could contribute to earnings.

The stock was quoted at C$11.56 in midday Toronto trade, after falling as low as C$11.52.

Goldman issued the report on Monday, when Canadian markets were closed for a public holiday.

BlackBerry's U.S.-listed shares fell 3.6 percent on Monday. They were little changed on Tuesday, rising 0.2 percent to $9.12. Goldman's price target is $8.50.

BlackBerry declined comment on Goldman's "sell" recommendation. Borges was unavailable for comment.

(Reporting by Alastair Sharp; Editing by Jim Finkle and David Gregorio)

By Alastair Sharp