The Glasgow No8, who has won 15 Scottish caps, undergoes an operation today on a hand injury after tearing a ligament in his left thumb during Friday evening’s 37-9 defeat by Edinburgh at Meadowbank.
Petrie’s enforced absence comes days after the Scotland coach, Ian McGeechan, learned that he will also have to do without full-back Ben Hinshelwood, who broke a leg in a club match.
"Unfortunately, the injury will mean that Jonnie will miss the Six Nations," Scotland team manager Doug Morgan confirmed, adding: "We wish him a speedy recovery.
Bristol captain Ross Beattie, who returned to the Scotland squad this season after recovering from injury, is the most likely player to benefit from Petrie’s absence. The more immediate effect has been to earn a training squad call-up for Andrew Wilson, the uncapped 22-year-old Glasgow back-row forward who will attend the Scotland squad session today at Murrayfield. Wilson was enlisted following the withdrawal of Petrie and the news that Edinburgh back-row forward Andrew Dall will require to be assessed by the Scotland medical team when he arrives today. Dall suffered a bang on the ribs when he was introduced as a substitute for Edinburgh in Friday’s match.
Wilson is in his first season of professional rugby. A product of the Ellon club he has honed his skills with Aberdeen GSFP and Heriot's FP and has played for Scotland at Students, Sevens, under-21 and under-19 levels.
The morning session at Murrayfield will be watched by the Conservative Party leader, Iain Duncan Smith.
London Irish and Northampton, the Powergen Cup finalists last season, will meet in the semi-finals on 2 March.
Irish, who beat Saints 38-7 at Twickenham last term, breezed into the last four with a victory over National League One title challengers Rotherham, and they will now face Northampton at the Kassam Stadium, the home of Oxford United.
The previous day, 1 March, Gloucester will tackle the European champions, Leicester at Franklin’s Gardens. Both games will be broadcast live by BBC.