Alldritt picked over Ollivon as France captain due to age profile
Scrum-half Dupont will miss the tournament, which starts on February 2, as the 27-year-old trains with France's seven-a-side squad before this summer's Paris Olympics.
No 8 Alldritt, 26, pipped flanker Charles Ollivon, 30, to the role, after the Toulon back-rower had been a consistent replacement for Dupont, with the next Rugby World Cup in Australia in three years' time.
"His age can also make us think, that like 70-80% of the team, he will be in Australia in 2027," Galthie told newspaper Midi Olympique.
"I hope with all my heart to take Charles to the World Cup but Greg is four years younger.
"Charles Ollivon is a highly liked captain by his teammates and the coaching staff.
"He is a figurehead of the French national team," the former France captain added.
Fluent English speaker Alldritt faces a tough challenge in his first match in the position by hosting last season's Six Nations Grand Slam winners Ireland in Marseille early next month.
