WATERLOO, ONTARIO — Amid rumors that once-dominant video rental chain Blockbuster would close all remaining 300 stores, smartphone maker BlackBerry Limited has announced plans to combine the firms in what is being lauded as the most promising merger in corporate history.

Although BlackBerry had itself been struggling to maintain financial viability and defend rapidly shrinking market share, analysts expect that the union of two once-iconic brands into “BlockBerry” will radically reform the competitive landscape of the smartphone and digital media industries.

In after-market trading, BlackBerry shares jumped almost $900 to close at a record high of $897.53, causing the company to eclipse Apple as the most valuable corporation on the planet.