*2.5. Agronomic Parameters and Heat Susceptiblity Index*

At the maturity stage, following agronomics parameters; plant height (PH, cm), number of tillers per plant (TPP), grain yield per plant (GY, g), straw yield per plant (SY, g), harvest index (HI) calculated by GY/total biomass, 1000-grain weight (GW, g), grain length (GL, mm), and normalized difference vegetative index (NDVI) were recorded. The heat susceptibility index (HSI) was measured for grain yield by using the formula:

$$1 - \left(\frac{\chi}{\mathbf{Y}\_{\mathbb{P}}}\right) / \mathsf{D}\_{\prime}$$

where Y is the grain yield under heat stress genotypes and Yp is the grain yield of genotypes under normal conditions. D is the stress intensity, which is measured by the formula:

$$\left(1 - \frac{\chi}{\chi\_{\mathbb{P}}}\right).$$

,

where X is the mean of the grain yield of heat stress genotypes and Xp is the mean of grain yield of genotypes under normal conditions [24].
