Salinity effect on water absorption, germination, growth and its relationship with varietal tolerance
Introduction
Among the adverse conditions of the agricultural systems of
the world, soil salinity is the factor that has influenced the
most on settlement of human populations. Approximately 43%
of the terrestrial surface used for the cultivation around
the world is affected by levels of salinity that, in most of the
cases, overcome the tolerance of the species of traditional
cultivations (1).
The percentage of salinity increases to a half rate of 0.5%
annually, mainly due to low rainfalls, high evaporation surface,
irrigation with saline waters and because of traditional
practices of cultivation that favor the increase of salts
concentration in the soil (2). Soil salinization
increases at a speed of 3,24 ha.min-1 (3) and
nowadays there are around 953 million hectares of lands
affected by this stressing factor in different regions of the
world.
Cuba, that has an agricultural surface of around 7.08 million
hectares, presents near a million hectares affected
by salinity and 1.5 millions have already potential
salinization problems (4) as a consequence at the
eastern region the 55% of the arable soils is
classified as salty soils. (5).
A partial solution to these problems is the installation of
crops and more tolerant varieties to salinity, that is why, it
is necessary to know this tolerance in a precise and
consistent way (6, 2). In the recovery and handling policies of
these soils, the use of tolerant species and varieties to salt
stress is
considered very important and it has received special
attention by different investigators in Cuba and
abroad (7). Concerning this topic, diverse authors (8, 6, 3)
state that to maximize the tolerance to salinity in arable
species is an important element in the integrated systems of
cultivation in areas affected by salinity and that, although this
theme has been investigated in several times, particularly
in the last 30 years, it do not complete all the
expectations and it is necessary to continue working in the
genetic improvement for this character.
Wheat, is one of the oldest species cultivated by man
and it constitutes, according to some reports (5),
the feeding base of more than 96.4% of the world
population, it is a rich food in energy and vitamins from
which more than 476 nutritious products are obtained, at the same
time it is an inigualable food for animals. This specie is
considered tolerant to the drought (9) and it
supports mean tenors of salinity (10, 4, 1), what transforms it
into a sustainable option for its use in affected areas by high
percentage of salts where the rehabilitation measures, like the
drainage, are both expensive and of difficult
execution.
wheat was introduced in Cuba, by the Spaniards,
since the first years of the conquest with a successful
production. The introduced varieties which were
acclimatizing until creating a very well adapted
variety that constituted a rarity inside the Spanish wheat
flora due to its good growing, development and yield (4). There
is already a great quantity of varieties introduced and
obtained in Cuba which show a very well genetic -productive
potential (4).
In Granma, Cuba, some projects of investigations
related to the introduction and validation of salt
tolerant varieties of wheat based on phenologic,
physiologic, biochemical, molecular and agricultural indicators,
are developed. Together whit these projects, an
investigation whose results are exposed in the present
document, was carried out contributing, this
way, to mitigate the problem of the saline soils. That is
why the monitory of the response to salt stress in
the available germoplasma, based on water absorption,
germination, growth and its relationship with varietal tolerance
would allow the choice of the existing genetic
variability for this character.
MATERIALS AND
METHODS
Three experiments were developed at the Nuclear
Technics laboratory of the Agricultural Researches Institute
"Jorge Dimitrov", Granma, Cuba. The first one with
the objective of determining the effect of different levels of
salinity that affect the absorption of water by the seeds during
the imbibition phase, another one to determine the effect of
different levels of salinity that affect the percentage of
germination of the seeds and the plants growth and a
third one with the purpose of establishing the degree
of divergence in the varietal tolerance, based on the
indicators studied at the initial phases of the development
of wheat plants .
In the first one, seeds of "Cuba-C-204" variety were
selected, it was the first Cuban variety obtained by
selection at the Fundamental Researches of Tropical
Agriculture Institute "Alejandro de Humboldt", starting
from the Brazilian floury wheat variety "BH-11", which were
put to absorb in petri badges at reason of 25 for badge with 10
ml of a solution of sodium chloride (NaCl) adjusted to
electric conductivities (CE) of 12; 15; 22; 25; 28
dS.m-1, as control was
used distilled water with an electric conductivity of 0.02
dS.m-1.
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