Samsonova, from Russia, defeated Sofia Kenin, 6-4, 6-0, while the Canadian native Fernandez knocked off Chloe Paquet of France, 6-0, 6-3.
The first four games of the Samsonova-Kenin match all featured breaks of serve, before both players steadied. Kenin had two break chances at 4-4, but could not convert, while Samsonova came through at 30-40 to win the first set. She cruised in 26 minutes, winning 26 of 35 points in the second set.
Fernandez captured her match in 65 minutes, winning 54 of 80 points (67.5%) contested.
Americans won in the two other main draw matches played on the first day of main draw competition. McCartney Kessler defeated Russia's Anastasia Pavlyuchenkova, 6-3, 6-3, while Hailey Baptiste rallied to edge Serbia's Teodora Kostovic, 4-6, 6-3, 6-4.
Transylvania Open
China's Yue Yuan upset sixth-seeded Antonia Ruzic of Croatia 6-4, 5-7, 6-2 on the first day of main draw competition on the indoor hard courts in Cluj-Napoca, Romania.
The match took 2 hours, 35 minutes and featured 14 breaks of service. Yuan, ranked No. 130, raced out to a 5-0 lead in the deciding set, failed on two match points in the sixth game, but prevailed on her next service opportunity.
The other seeded player in action, No. 8 Anna Bondar of Hungary, won a three-setter over Germany's Ella Seidel, 4-6, 7-6 (6), 6-0. Seidel took an early 3-1 lead in the second-set tie-breaker, but Bondar won four straight points to take control.
In the other two main draw matches, Spain's Sara Sorribes Tormo upset Bulgaria's Viktoriya Tomova, 6-2, 7-5 and Ukraine's Oleksandra Oliynuykova ousted Egypt's Mayar Sherif, 6-7 (6), 6-4, 6-4.
Ostrava Open
Sixth-seeded Caty McNally knocked off Suzan Lamens of the Netherlands, 6-3, 7-5, on the first day of main draw action in Ostrava, Czech Republic.
No. 8 Hungarian Panna Udvardy edged Darja Vidmanova of the Czech Republic, 7-5, 6-3, but seventh-seeded Moyuka Uchijima of Japan fell to Armenian Elina Avanesyan, 6-3, 2-6, 6-3.
McNally trailed, 4-2, in the second set, but broke Lamens' serve and eventually evened the set at 5-5. In an 11-point 11th game, the Cincinnati native broke for the sixth time in the match and held at love to triumph.
In the two other main draw matches, Katie Volynets routed Poland's Linda Klimovicova, 6-2, 6-1, while the host nation's Tereza Martincova stunned Hungary's Dalma Galfi, 2-6, 6-3, 7-5. Martincova is ranked No. 469, while Galfi is at 91.