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BREEDING TOLERANT CULTIVARS FOR HIGH SALINITY STRESS CONDITONS

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BREEDING TOLERANT CULTIVARS FOR HIGH SALINITY STRESS CONDITONS

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Page 1: BREEDING TOLERANT CULTIVARS FOR HIGH SALINITY STRESS CONDITONS

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

Page 2: BREEDING TOLERANT CULTIVARS FOR HIGH SALINITY STRESS CONDITONS

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.