Click here to load reader
Upload
cappunu
View
25
Download
0
Embed Size (px)
DESCRIPTION
BREEDING TOLERANT CULTIVARS FOR HIGH SALINITY STRESS CONDITONS
Citation preview
BREEDING TOLERANT CULTIVARS FOR HIGH SALINITY STRESS CONDITONS
C. Mahadevaiah1, C. Appunu1, V. Sreenivasa1, T. Manjunatha1, G.S. Suresha2
1Division of Crop Improvement, 2Division of Crop Production, Sugarcane Breeding Institute, Coimbatore
Salinity is a major environmental stress and is a substantial constraint to crop production.
Salinity is a significant factor limiting agricultural productivity and affecting about 9 x 10 8
hectares worldwide. Almost all the crops are affected by soil salinization. Poor quality of water
for irrigation and current unsustainable irrigation practices has significantly resulted in
salinization and other forms of soil damage. About one third of all irrigated land is affected by
salt due to secondary salinization. Increased salinization of arable land is expected to have
devastating global effects, resulting in 30% land loss within next 25 years and up to 50% by the
middle of 21st century. The problem of secondary salinization is also becoming more serious as
it represents loss of highly productive lands.
High salinity causes both hyperionic and hyperosmotic stress and can lead to plant
demise. Sea water contains approximately 3% of NaCl and in terms of molarity of different ions,
Na+ is about 460 mM, Mg2+ is 50 mM and Cl- around 540 mM along with smaller quantities of
other ions. Salinity in a given land area depends upon various factors like amount of evaporation
(leading to increase in salt concentration), or the amount of precipitation (leading to decrease in
salt concentration). Weathering of rocks also affects salt concentration. Inland deserts are marked
by high salinity as the rate of evaporation far exceeds the rate of precipitation. Agricultural lands
that have been heavily irrigated are highly saline. As drier areas in particular need intense
irrigation, there is extensive water loss through a combination of both evaporation as well as
transpiration. This process is known as evapotranspiration and as a result, the salt delivered along
with the irrigation water gets concentrated, year-by-year in the soil. This leads to huge losses in
terms of arable land and productivity as most of the economically important crop species are
very sensitive to soil salinity. These salt sensitive plants, also known as glycophytes include rice
(Oryza sativa), maize (Zea mays), soybean (Glycine max) and beans (Phaseolus vulgaris). High
salt concentration (Na+) in particular which deposit in the soil can alter the basic texture of the
soil resulting in decreased soil porosity and consequently reduced soil aeration and water
conductance. Thus developing plant varieties with potential to tolerate high saline conditions
might help to maintain agricultural production.