The present work aimed to study the correlation between resistance against
Orobanche and the tolerance to salinity in some parasitized Vicia faba resistant
cultivars, i.e. Giza 429 and Giza 843-, as well as the partially resistant Giza 674
cultivar in comparison with the susceptible Giza 3 one, through the evaluation of their
growth, chemical composition and productivity when irrigated with different levels of
sea water (5% and 10% as continual irrigation as well as 10% and 20% as alternately
irrigation, E.C. 2.5, 5.0, 5.0 and 10.0 ds/m, respectively), in addition to the fresh water
irrigation in the control treatment in the first pot experiment season; 199912000, or
when irrigated with the same levels of salinity in the presence of Orobanche
parasitiern in the second one; 200012001. The obtained data in both growing seasons
represent a strong supportive evidence on the highly degree of the physiological
tolerance not only to salt stress but also to the double stresses (salinity + Orobanche
infection), which characterized both Orobanche-resistant cultivars; Giza 429 and Giza
843 that enable both of them to be adapted to even the double stresses.thue. could
complete its life cycle till harvest, and produced its seed yield under such conditions
without applying any specific treatments that induce such adaptation. Meanwhile, the
non-adapted Giza 674 and Giza 3 cultivars were not able to do so under the same
conditions. The recorded results with both resistant cultivars disclosed that this
physiological tolerance brought about in both of them by creating more negative
osmotic potentials (Osmotic Adjustment) through the accumulation of much more
quantities of inorganic osmotica, Le. N, P, K+, Ca+², Mg+2 and the lowest quantities of
Na+ and lower Na+/Ca+²ratio as well as high K+/Na+ ratio, this in addition to the
considerable accumulation of organiC protective osmolytes, i.e. sugars (especially
non-reducing ones), proline, free amino acids and protein in their roots and shoots,
which greatly exceeded either that in the stressed plants of the other two cultivars or
even the non-stressed control plants in several cases. Such accumulation increased
proportionally with increasing salinity level as an adaptable mechanism with enable
both cultivars to adjust the rate between the protective and toxic intermediates of
metabolism in favor of more tolerance to stress. Since, the accumulating of much
more quantities of sugars (as osmolytes) in their roots might enable plants to keep
better water relation under stress conditions, by increasing the ability of their roots to
extract more water even from the saline soil solution. Moreover. the calculating of
Relative Seed Yield % [RSy] and Stress Susceptibility Index % [SI1 values for the
tested cultivars offered another strong evidence on the high tolerance to salinity, as
did against Orobanche infection, which characterizing both Giza 429 and Giza 843
cultivars. In the meantime, the highly significant values of correlation coefficient for
botl' mentioned cultivars strongly confirmed the highly Significant positive correlation
between Orobanche resistance and salt tolerance in both Orobanche-resistant
cultivars, which was the main interesting point in the present investigation.
Nevertheless, the all applied stress treatments resulted in a highly significant
reduction in the yield components of both resistant cultivars in spite of their superiority
as regards growth, dry weights and chemical composition in comparison