Abstract:
Drought tolerance is a complex trait that involves different biochemical
and physiological mechanisms in plants. It was the objective of the
present study to evaluate the agronomic and biochemical responses of
triticale, tritipyrum, and wheat to drought stress. For this purpose,
twenty-seven genotypes were evaluated under two levels (non-stress
and drought stress) of irrigation during 2015‒2017. The metabolic traits
studied included relative water content (RWC), membrane stability index
(MSI), chlorophyll a (Chla), chlorophyll b (Chlb), carotenoids (Car), leaf
proline content (Pro), leaf soluble carbohydrates (LSC), glycine betaine
(GB), malondialdehyde (MDA), hydrogen peroxide (H2O2), seeds per spike
(SS), seed weight (SW), biological yield (BY) and seed yield (SY). Drought
stress increased Pro, LSC, and GB contents as well as lipid peroxidation
through increasing MDA and H2O2 activities. However, both RWC and
MSI indices as well as SS, SW, SY and BY reduced as a result of drought
treatment although the least decrease of SY was observed at triticale
group. During the two years of study, the tritipyrum genotypes exhibited
their drought tolerance by accumulation of more LSC and GB as well as
lower decrease in SW while the triticale ones responded by maintaining
higher levels of RWC but producing less MDA and H2O2. It may, therefore,
be concluded that the three species studied exploit different
mechanisms to maintain tolerance against drought stress. Finally, correlation
analysis indicated the positive effects of LSC on SY under both
drought and normal conditions, which is obviously a promising trait in
wheat, triticale, and tritipyrum that can be beneficially exploited in
drought tolerance improvement programs
