Crosses were made between the cultivars Tema and Oxyra, which are tolerant to drought, as well as cv. Giza-6, Emy and Sigme, which are susceptible to drought, to study the inheritance and nature of drought tolerance and some related characteristics which may have direct or indirect effects on drought tolerance. There were highly significant differences between the previously mentioned parental cultivars concerning root characters, i.e. root length, fresh and dry weight under normal irrigation and drought conditions in pot experiment. There were highly significant increase percentages in root length in P1, P2 and F1 for each cross under water stress conditions compared with this percentage under normal irrigation. On the other hand, there were highly significant decrease percentages in root fresh and dry weight under water conditions. There were slight partial dominance for high root length and fresh and dry weight.
Drought tolerance, leaf water loss ratio, total yield/plant and leaf proline content were inherited quantitatively. Partial dominance was detected for high level of drought tolerance, total yield/plant and leaf proline content over low levels. Whereas, partial dominance were found for low level of leaf water loss ratio over high leaf water loss ratio. Broad sense heritability for drought tolerance, leaf water loss ratio, and total dry seed yield/plant and leaf proline content ranged from intermediate to high. Meanwhile, narrow sense heritability for the same characters ranged from low to above intermediate. Number of major genes controlling drought tolerance, leaf water loss ratio, total dry seed yield/plant and leaf proline content ranged from 1 to 4, 1 to 3, 1 to 4 and 3 gene pairs, respectively.
Drought tolerance was positively correlated with each of number of branches/plant, number of pods/plant, fruit set percentage, as well as with number of seeds/pod, 100 seed weight and total dry seed yield/plant. On the other hand, drought tolerance was negatively correlated with each of number of days from sowing date to the first flower bud anthesis, leaf water loss ratio and leaf area. Free proline content of plant leaves was positively correlated with each of drought tolerance, number of branches/plant, number of seeds/pod, 100 seed weight and total dry seed yield/plant. On the contrary, there was highly significant negative correlation between free proline content of leaves and each of number of days passed from sowing date to the first flower bud anthesis, leaf water loss ratio and leaf area. There were highly significant regression between drought tolerance and each of number of days required from sowing date to the first flower bud anthesis, number of branches/plant, fruit set percentage, 100 seed weight, total dry seed yield/plant, leaf water loss ratio and leaf area.
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