Evaluation of Salinity Stress Evaluation of Salinity Stress Tolerance in Mango (Tolerance in Mango (Mangifera Mangifera

indicaindica L.) Genetic Resources – L.) Genetic Resources – Way Way forwardforward

H RavishankarH Ravishankar, VK Singh and Sridhar Gutam, VK Singh and Sridhar Gutam

Central Institute for Subtropical HorticultureCentral Institute for Subtropical HorticultureRehmankhera, Kakori Post, Lucknow 227107,UPRehmankhera, Kakori Post, Lucknow 227107,UP

EmailEmail: : drhravishankar@gmail.comdrhravishankar@gmail.com

2nd National Seminar on Management of Salt affected Soils and Waters: Challenges of the 21st Century.

CSSRI, RS, Lucknow. March 16-17, 2012

Mango – King of the Mango – King of the FruitsFruits

Area: 2.31 Mha (NHB,

2012)

Prod.: 15.02 M MT High Demand Low Supply Export: -18% (APEDA,

2012)

CISH

Wikipedia

CISH Vision 2030 - Towards CISH Vision 2030 - Towards Mitigation of Abiotic StressMitigation of Abiotic Stress

ConstraintsConstraintsGlobal climatic changes among other paradigms also envisage augmented salinization of agriculturally suited landmass.

Central Institute for Subtropical Horticulture (CISH), Lucknow, in its Vision 2030 document under the Strategy and Framework has prominently flagged the need for development and standardization of rootstocks as one of the major resilient strategies for addressing the abiotic stress constraints in mango.

Soil Salinity & Mango in Soil Salinity & Mango in IndiaIndia

Salinity and Alkalinity affected soils: 8.4 Mha (Singh et al., 2012).

Great possibility exists to bring some of these problem areas under mango cultivation.

Mango (Mangifera indica L.), the king of fruits is highly sensitive to soil salinity and alkalinity.

Therefore, its expansion in such affected areas for profitable cultivation becomes greatly restricted.

FAO

Adverse Effects & Adverse Effects & Management Management

StrategiesStrategiesAdverse effects of salinity on plant

growth could ensue due to the ion

cytotoxicity (Na+, Cl- and SO4-) and

osmotic stress.

Strategies to confer salt tolerance in

general include :

Ion exclusion, ion sequestration, osmotic

adjustments, macromolecule protection

and membrane transport system

adaptation to saline environments.

Mechanisms of Salinity ToleranceMechanisms of Salinity Tolerance

Plants have adapted a variety of mechanisms of salt tolerance

The mechanisms include:

Salt exclusion

Salt excretion

Osmotic adjustment

Membrane compositionGrosso and Bickel, 1999

Moisture stress

Decreased leaf water potential/tissue water status

Loss of turgor

Reduced metabolic activities of cells

Reduced growth and productivity

Cellular Level Tolerance Cellular Level Tolerance Maintenance of cellular metabolic activities under low tissue water status becomes a very crucial aspect.

This can be achieved by cellular level tolerance (CLT) mechanisms

Mechanisms of Salinity Mechanisms of Salinity ToleranceTolerance

Genes related to Oxidative stress management Superoxide dismutase, Glutathione transferase

like enzymes play role in reducing ROS damage.Genes related to Osmotic adjustments

Osmoprotection – desiccation tolerance -Cod A – rate limiting enzyme in production of Glycine Betaine

Genes related to Osmolytes - Proline, Trehalose Genes related to Cellular level tolerance

Aquaporins, Plasma membrane intrinsic proteins (PMIPs) regulate water movement and water balance.

Co-expression of regulatory genes (DREB, ZIP, MYC), with house keeping genes (DNA helicase involved in DNA unwinding).

Heat shock proteins (HSPs) Late embryogenesis abundant (LEA) protein and Binding proteins (BIPs) are chaperones involved in protein folding and turn over.

Mango RootstocksMango RootstocksInternational and National International and National

scenarioscenario• Mangifera indica L. cv. 13-1 of Israel is

commercially adopted as a rootstock where

calcareous soils and saline irrigation water

pose serious problems in mango cultivation in

Israel.

• This rootstock introduced to India sometimes

back is yet to be adequately tested and

exploited for different scion varieties.

Currently large scale trials are being planned

in Gujarat.• In Spain however, association of salt tolerance features of

Gomera-1 (Mangifera indica L.) is related to its capacity to

restrict the uptake and transport of Cl- and Na+ ions from the

rootstock to the above ground parts.

• Further in the study, Cl- ions were found more toxic in rootstock

and cultivar leaves while Na+ ions were more toxic in roots.

• (Zuazo, 2004)

Wikipedia

Evaluation of Polyembryonic Evaluation of Polyembryonic Rootstocks Variability for Salinity Rootstocks Variability for Salinity

ToleranceTolerance - CISH - CISH

Membrane stability varied among the polyembryonic accessions (Bappakai, Goa, IC202224, IC470676, Komanga, Kulambe, Kurukkan, Moovandan, Mylepaliun, Nekkare, Nattumanga, Olour, Pullian, Ratnagiri, Thrissur and Vellai Columban) and it is in the range of 58% - 86% when studied under open conditions.

Bappakai could tolerate salinity levels up to 5.3 dSm-1

However, further studies on these accessions exposed to salt stress needed.

M. zeylanica Hooker f. recorded a higher

K/Na ratio in all plant parts especially in

the roots implying that it manifested

greater salinity tolerance than M. indica

L. cv. 13-1

continued…..

Another feature of salt

tolerance is to maintain

higher degree of

membrane stability under

salt stress situationsWikipedia

Schmutz, 1999

Physiological DescriptorsPhysiological Descriptors

CO2 assimilation, Root respiration and Carbon gain-found as useful tools in discriminating salt tolerance between M. indica L. cv. 13-1 and M. zeylanica Hooker f.

In that M. zeylanica Hooker f. recorded higher rates of CO2 assimilation, root respiration, relatively low Na+ and Cl- contents but had higher K+, Ca++ as well as Mg++ in the leaves. Schmutz, 1999

ChallengesChallenges

• Narrow genetic base of polyembryonic mangoes- need for widening of genetic base

• Polyembryony is inherited as a recessive trait under the control of single dominant gene

• Lack of diverse rootstocks with tolerance to salinity

• Limited genomic resources for identification of genetic potentials of tolerance mechanisms

• G x E interactions and rootstock-scion compatibility

• Identification of genotypes with specific traits for salt tolerance- Transcriptome profiling, QTL mapping and MAS to tag genes

• Development of standard reliable protocols for screening against salt tolerance

Wild Mangoes – Sources of Salt Wild Mangoes – Sources of Salt Tolerance ?Tolerance ?

M. odorata

WikipediaWikipediaWikipedia

M. foetida

Way forwardWay forward : : Wild Wild Mangoes?Mangoes?

• Some of the wild mangoes (allied species of Mangifera)

dominating the South China Sea viz., M. laurina, M.

odorata, M. pajang and M. foetida that await genetical

characterization may serve as useful gene donors in

this regard

• Mangifera spp. / ecotypes endemic to the Andaman and

Nicobar islands may also provide useful insights – co

evolution with saline environments; coastal ecosystems

• Pyramiding and stacking multiple genes controlling

different aspects of salt tolerance in mango needs focus