The pollen grains of 10 homozygous inbred lines were subjected to heat stress (36°C) for 2 and 4 hours duration in the laboratory and cultured on agar pollen germination medium. High temperature treatment completely inhibited pollen germination and tube growth in seven inbred lines and only moderately in 3 lines - BTM 14, BTM 15 and BTM 1 suggesting the genetic variability for gametophytic heat tolerance among selected inbred lines. Heat treated pollen grains were also used to self-fertilize the field grown plants of ten inbred lines. High temperature stress significantly reduced the seed set in all the inbred lines. However two inbred lines BTM 14 and BTM 15 produced relatively more number of seeds per cob suggesting their tolerance to heat stress. The lines which showed gametophytic tolerance to heat stress under in vitro conditions produced more number of seeds per cob after heat treatment to pollen grains. © Society for the Advancement of Breeding Research in Asia and Oceania.