3.1.1. Membrane Stability Index (MSI)
The characterization of wheat genotypes contrasting in their response to drought stress was performed by checking membrane stability index. The results showed that the mean value for membrane stability 55.227 was recorded in control 100% field capacity. Similarly in drought condition 80% field capacity the mean value for membrane stability was 60.69 was recorded. Likewise in severe drought condition 60% field capacity condition the mean value 54.106 was recorded. (Table. 1, Fig. 1) Analysis of variance (ANOVA) regarding MSI revealed that the effect of drought stress is highly significant while genotypes and their interaction with different level of drought stress are non-significant as shown in (Table 2). The least significant difference (LSD) showed that in normal condition 100% field capacity the membrane stability not different significantly and stay-green chirya-1 genotype showed maximum 58.415 membrane stability index followed by SD-32. In drought condition 80% field capacity and 60% field capacity the means are not significantly different from each other and highest value for membrane stability 62.685 and 55.966 were recorded for SD-28 wheat genotype respectively (Table 3).