What are the best seed strains for growing in a region of the world where the photo period is 12/12 hours.

If you live near the Equator the south Indian varieties from Tamil and Madya  Pradish  would  do  very  well. These  plants are
very vigorous and flower abundantly in India's hot, dry summers.

• Hindu Kush
• Light of Jah
• Master Kush
• Shiva Shanti

These varieties are adapted to flower in November and December in India, but with the slightly shorter days in other regions, they will flower a little earlier, maturing in November.

Other varieties that you also might grow are land races from Thailand, Cambodia, Jamaica and Brazil and some of the central African countries.

• 4 Way (Four way)
• Afghani

You could try some of the mostly Sativa commercial varieties.  These  are  adapted  for  higher  latitudes  so they will flower several months earlier where you are, ripening in September and October.  The  Haze  varieties  may  also  be  of some use. However, your best program might be to use well-adapted Sativas and to make  your  own crosses  with  Indicas  or Indica-Sativa hybrids.

• Durban Poison
• Purple Power
• Haze
• Super Silver Haze

Backcrossing tropical hybrids with Indicas or Sativa-Indica hybrids produce shorter, more controlled plants than  the two to three-meter Sativa giants. With 25% Indica heritage, these plants will begin flowering and will mature in October, one to one and a half months earlier than the purebreds.

Good Luck !!