الفهرس 
The family BrassicaceaeOnly 14 pages are availabe for public view
 |  | from | 107 |  |  |
| | | from | 107 | | |
Abstract
Brassicaceae is regarded as one of the most economically important plant
groups worldwide, which consists of many substantial fodder crops, for
example, Brassica napus, Brassica rapa, and Brassica oleracea (Gómez-
Campo 1999) . Brassica species are broadly used in human food mostly as
a necessary source of vegetables, palatable oils, and condiments (Al-
Shehbaz 1984; Gómez-Campo 1999; Raza et al. 2020) . Brassica regarded
as one of the greatest important genera of the Brassicaceae which
containing up to 100 groups such as cauliflower, brussels sprouts,
broccoli, various mustards, and turnip (Gómez-Campo 1999) .
Brassica oleracea (B. oleracea) wild forms largely exist in costal terrains
of Western Europe (Warwick 2011) . Brassica oleracea species is the
main constituent of the diets in many nations of the developing countries.
It is rich in minerals, dietary fiber, vitamin A, B1-2, C, E, and K (Fahey
and Talalay 1995; Raza et al. 2020; Wink and Van Wyk 2008) and other
possible beneficial factors, such as anti-cancer agents' compounds (Fahey
and Talalay 1995) .
Plants are suffered from various environmental stresses involving abiotic
and biotic stresses. Drought is one of the most critical abiotic stresses
which negatively affect plant progress and development is (Rana et al.
2013; Zlatev and Lidon 2012) . Drought is a natural phenomenon, which
exists in both developing and developed countries and all communities
(Dai 2013) . Global climate changes are the major factor causing drought
stress all over the world (Mishra and Singh 2011; Rana et al. 2013) .
Nevertheless, there are numerous other causes for drought, such as high
temperature, high intensity of light, and dry wind, all of which induce
16
evaporation of water from the soil (Dai 2013) . Otherwise, there is enough
water in the soil, but plants cannot absorb it due to several conditions, for
example, flooding, low soil temperatures, and salinity. This kind of water
stress is known as a pseudo-drought or physiological drought (Arbona et
al. 2013; Athar and Ashraf 2009) . Plants make several physiological,
morphological, molecular, and biochemical reactions to adapt to water
scarcity. The responses range from a molecular level to a whole plant
level (Beck et al. 2007) . The checkup of drought tolerance during
different growth periods is necessary to disentangle the problem of
drought. Brassica oleracea can be regarded as moderately or sensitive
tolerant to cases of abiotic stress such as drought and salinity (Beacham et
al. 2017; Zhang et al. 2014) .
A variety of approaches were used to ease the problem of drought, plant
breeding, either conventional breeding or genetic engineering, seems to
be an effective and economical means of adapting crops to enable them to
grow successfully under drought stress conditions. Although plant
breeders achieved generous progress through conventional breeding and
developed drought-tolerant cultivars for some selected crops, this
approach is costly and consuming time and effort. Otherwise, marker-
assisted breeding is the more effective approach, which can identify the
usefulness of thousands of genomic regions of the crop under stress
situations. With the development of ample molecular association maps,
marker-assisted selection procedures directed to pyramiding needed traits
to enhance the crop drought tolerance (Ashraf 2010) . Many studies dealt
with the drought tolerance in brassica oleracea that concerned with
morphological, physiological traits and biochemical properties (Sahin et
al. 2018; SPROUTS 2018) . Compared to other species such as Brassica
napus and Brassica rapa, there are QTL studies for drought tolerance
(Gad et al. 2021; Lu et al. 2008) .
17
To the best of our knowledge, there are no studies dealt with identifying
QTL for drought on Brassica oleracea. Therefore, we prepared this study
to identify the different QTLs related to drought tolerance in Brassica
oleracea. In our study, 105 (DH) double haploid lines of Brassica
oleracea were exposed to PEG-induced drought during seed germination.
Drought stress "17% PEG" reduced the seed germination and seedling
associated traits except for root length, protein, and proline content were
increased under drought in comparison to control. Quantitative trait loci
were used to recognize genomic regions related to our trait of interest.
Thirty-nine QTLs were detected and dispersed across the nine
chromosomes of Brassica oleracea. Twenty-nine QTLs were identified
under both control and drought conditions, eleven QTLs were detected
under control on seven linkage groups, eighteen QTLs were detected
under drought on eight linkage groups, also ten QTLs were identified for
drought tolerance indices for germination percentage, germination pace,
germination rate index, fresh weight, Timson germination index and
protein on five linkage groups. It was no QTLs for proline.
The present study provides an important genetic source of developmental
and adaptive traits in Brassica oleracea that is significant to be used in
the future work of hereditary and breeding.
8.1 Aim of the work
1- To evaluate the seed germination under drought stress.
2- Studying and treating the effect of drought on seed germination in DH
mapping population of Brassica oleracea and identifying the QTLs that
control the variation in the calculated germination parameters under
control and drought stress.
3-Mapping of QTL controlling seed germination under both control and
drought treatment.