Yes, Jiraya taught the Summoning Jutsu to Minato Namikaze.
Jiraya was the sensei of Minato, and its observed in some episodes of the anime that Jiraya taught him many jutsu including the the Summoning Jutsu, though the training is not directly shown .
Jiraya was used to be the carrier of the Scroll of Blood Contract, after he earned the
trust of the toads.
Since, Jiraya took special interest in his student, so he entrusted the Summoning Jutsu technique with minato to make him more powerful in combat.
Also, the toads especially Fukusaku respect both Jiraya and Minato and once was quoted saying " Naruto has surpassed both of 'em the Student(Minato) and his Master(Jiraya) ".
So maybe in training with toads, Jiraya may have helped Minato @Mount Miyoboku.
Hence, he must've taught minato the technique.
Also, the order in which their names appear on the script may not be known or quoted anywhere in the anime. Maybe that is due to the fact that if someone dies beyond the scope of reanimation jutsu, his( toad or human) name vanishes from the script
(Ref- Anime episode when Pain attack Hidden Leaf Village, and Danzo kills the Messenger Frog. Other frog inform Ma Frog that the name of the Messenger frog has vanished from the scroll.)
Hence, Minato's name would have been written in the blank space created so....