Only 11 of the 144-strong field, battling against a strong wind, broke par at the Islantilla Golf Club near Huelva, Spain.
Smyth and Luna lead another Spaniard, Miguel Angel Martin, and the Welshman Philip Price by one shot while Jose Maria Olazabal, was trailing on 72. The European Ryder Cup player was playing his first tournament round since November following a winter break and an operation on his right big toe.
He looked as if he would be challenging for the lead when he was two under par with four holes to play, but the 29-year-old Spaniard, who began at the 10th and had all the most difficult holes behind him, bogeyed three of his last four to finish hugely disappointed.
Smyth, who had five birdies and only two bogeys, said: "I thought very hard about this course before I went out because it can murder you if you hit bad shots."
Luna had the distinction of being the only player not to have a single bogey but still had to birdie the last to catch Smyth late in the day. The 32-year-old Spaniard, who won the Madeira Island Open last month, said: "My short game was fantastic and that was the key to my score. This is a very dangerous golf course."
ANDALUCIA OPEN (Huelva, Sp) First round scores (GB or Irl unless stated): 68 D Smyth, S Luna (Sp); 69 P Price, M A Martin (Sp); 70 S Torrance, W Riley (Aus), I Palmer (SA), F Tarnaud (Fr), M Mouland, F Valera (Sp), D Hospital (Sp); 71 C Rocca (It), P Quirici (Swit), J Bickerton, E O'Connell, P McGinley, A Cejka (Ger), P Hedblom (Swe), J Robson; 72 D Borrego (Sp), J M Olazabal (Sp), J M Canizares (Sp), V Fernandez (Arg), P Linhart (Sp), A Mednick (Swe), M Hallberg (Swe), A Hunter, M Davis, J Pinero (Sp), A Sherborne, P Mayo, M Farry (Fr), T Munoz (Sp), M-A Jimenez (Sp), O Karlsson (Swe), J Quiros (Sp), R Claydon, J Mellor, L White, A Bossert (Swit); 73 P Simpson, A Forsbrand (Swe), P Mitchell, L Westwood, S Struver (Ger), P Affleck, C Suneson, A Coltart, S Lyle, J McHenry, D Carter, M Gronberg (Swe), D Cooper, S McAllister, R McFarlane, P Teravainen (US); 74 R Burns, E Darcy, J Lomas, J Hawksworth, A Binaghi (It), K Eriksson (Swe), R Chapman, M Gates, S Tinning (Den), D Williams, M Moreno (Sp), D Higgins, R Karlsson (Swe), B Lane, D Lee, S Grappasonni (It), P-U Johansson (Swe), P Broadhurst, G Emerson, D R Jones, J Arruti (Sp); 75 D Gilford, J Rivero (Sp), P Fulke (Swe), M McLean, C Cevaer (Fr), R Muntz (Neth), A Oldcorn, M Gortana (It), R Drummond, C Mason, S Richardson, M Pinero (Sp), J Gronhagen (Swe).Reuse content