High temperature is one of the abiotic stress causing morphological, physiological, biochemical and molecular changes on plant growth and productivity. One hundred and sixty cotton genotypes obtained from genetic stocks was evaluated for high temperature tolerance based on some agronomic characters under field and controlled conditions. Genotypes showed differences for all investigated characters. Plant height, node number and HNR ranged from 68.38-136.45 cm, 18.22-30.10 number.plant-1, 2.89-6.31 (HNR) respectively. Maximum and minimum values in terms of number of sympodial branches, boll abscission at first position, number of seed and seed-cotton yield changed from 11.09-24.42 number.plant-1; 4.17%-20.80%; 20.39-44.11 number.boll-1 and 5.74-60.30 gr.plant-1 respectively. Differences among genotypes were statistically significant for all characters under high temperature stress conditions. High temperature stress was declined the cotton plant development, the decline are important for cotton breeders and cotton breeding programs on the genotypes less affected from high temperature.This work was supported by the Scientific and Technical Research Council of Turkey (TUBITAK) under Grant No. TOVAG-109O339
