Abstract
The present study was conducted with the objective to assess germplasm of American cotton for heat tolerance using canopy
temperature. For this purpose seventy varieties/lines of Upland cotton were screened out at flowering stage. Analysis of
variance revealed significant differences among the germplasm lines. Three tolerant (MNH552, FH1000 and NIAB111) and
three susceptible lines (Cedix ST-362 (GL), LRA5166 and 4F) were selected. The tolerant and susceptible genotypes were
crossed to develop F1 seed of the three crosses. Six generations i.e. F1, F2, BC1 and BC2 of each cross were grown along with
their parents under normal and high temperature in the field following RCBD with three replications. At flowering stage,
canopy temperature was measured in both the temperature regimes. Indices of heat tolerance were calculated for genetic
investigation. Generation means analysis of the data revealed that additive, dominance and epistatic component were
involved in the inheritance of canopy temperature. However genetic variance analysis showed that canopy temperature was
predominantly controlled by additive genes, and thus estimates of h2
ns were high. These results suggest that rapid
improvement in reducing canopy temperature of the plant material is possible through breeding and selection in F3
population.
