*3.1. Average Performance of Cotton Varieties Based on Morpho-Physiological Traits*

Based on statistically significant differences for various morpho-physiological characteristics, two cultivars, MNH-886 and MNH-814, were selected. Significant variations in heat tolerance characteristics were observed among both varieties. The mean value for fully dehiscent anthers (FDA) was 92 and 64 for MNH-886 and MNH-814 respectively. MNH-814 showed less pollen viability (66.4) than MNH886 (88.3). SNF was 34 for MNH-886 and for MNH-814 its average value was 27 (Figure 2a). The trait PBF average data of both parents were 51 and 38. MNH-886 showed less CIY while exposed to high temperatures, with an average value of 65, while MNH-814 was susceptible to extreme temperatures and the CIY was greater, with a value of 80.

Likewise, MNH 886 excelled in NOB with an average value of 23 while MNH-814 showed 12 TNN under heat-stress conditions. MNH 886 showed TNF even under heat stress with an average value of 35 while MNH 814 showed retention of a smaller number of flowers with an average value of 23. Maximum variation was observed in trait PCO; its value was 5.3 for MNH-886 and 76.6 for MNH 814. The average values of morphophysiological traits showed that both varieties vary in most of the traits and showed that MNH-886 excelled in heat tolerance considering each trait compared with other cultivars, while MNH-814 was the most susceptible as compared with other varieties (Table 2).

Phenotypic distribution of F2 population for morpho-physiological traits is shown in Figure 2a,b. The phenotypic values of morpho-physiological traits are presented in Table 3. Twenty-one morpho-physiological traits displayed a normal distribution (skewness did not exceed 1.0), while two traits, TNF and NOB, showed a non-normal distribution. These results indicated the trend of having major QTL involvement in this population and it was thus suitable for QTL analysis.

**Figure 2.** *Cont.*

**Figure 2.** (**a**,**b**) Frequency distribution of morpho-physiological traits related to heat stress across F2 population.


 **2.** Mean values data for 23 morpho-physiological traits of fourteen cotton cultivars.

**Table**

**NN3**

68

 20

 35

 7.5

 30

 22

 25

 3.4

 2.6

 2.1

 2.6

 42.2


**Table 2.** *Cont.*


**Table 3.** Phenotypic values for heat tolerance traits of F2 population and their parents.
