*2.3. Mapping Population*

Based on highly significant differences between two parental lines, the F2 population was developed by self-pollinating F1 plants from a cross between upland cotton line MNH-886 (a heat-tolerant cultivar), and MNH-814 (a heat-sensitive cultivar), and was used to map HT-QTLs during different morphological stages in cotton. Five plants were tagged at random in each line for recording physiological traits data. Ninety-four plants from the F2 population were selected to derive phenotypic and molecular data along with two parents. The experimental field area of Cotton Research Station Multan under natural conditions was selected for experiment to coincide the reproductive phase with higher temperature.
