Quantitative trait loci (QTL) for salinity tolerance traits in interspecific hybrids of Eucalyptus

Soil salinity is one of the major limiting factors in productivity of plants. Cultivation of industrially important fast growing saline tolerant tree species is one of the options to reclaim the saline soils. Some of the Eucalyptus species are salt tolerant and production of interspecific hybrids of these species would enhance productivity in saline environments. In this study, phenotypic parameters for growth, physiology and mineral nutrition were estimated in Eucalyptus camaldulensis × E. tereticornis F1 hybrids to understand the mechanism of salinity tolerance and localize quantitative trait loci (QTL) involved in sodium chloride (NaCl) stress. Salt injury scoring and plasma membrane damage showed a significant difference between tolerant and susceptible individuals, which was correlated with the gas exchange measurements and Na, K and K/Na ratio. Under salinity, correlation of gas exchange measurements showed strong positive correlations between the traits, Anet, gs, Ci and E indicated the role of stomatal function. It was inferred that sequestration of NaCl by the salt tolerant individuals was through compartmentalization of Na and its detoxification by maintenance of K/Na ratio. Totally, 33 QTL were identified under salinity and control conditions. Co-localization of QTL regulating Na and K transport substantiated their influence in salinity tolerance which could be due to the closely linked genes or by pleiotropic effect of same genes on these traits. Fine mapping with more molecular markers will locate the QTL precisely and validating with field trails could hasten the traditional methods for salinity breeding.