Na+ transporter HKT1;2 reduces flower Na+ content and considerably mitigates the decline in tomato fruit yields under saline conditions.

Genes encoding HKT1-like Na+ transporters play a key role in the salinity tolerance mechanism in Arabidopsis and other plant species by retrieving Na+ from the xylem of different organs and tissues. In this study, we investigated the role of two HKT1;2 allelic variants in tomato salt tolerance in relation to vegetative growth and fruit yield in plants subjected to salt treatment in a commercial greenhouse under real production conditions. We used two near-isogenic lines (NILs), homozygous for either the Solanum lycopersicum (NIL17) or S. cheesmaniae (NIL14) allele, at HKT1;2 loci and their respective RNAi- Sl/ScHKT1;2 lines. The results obtained show that both ScHKT1;2 - and SlHKT1;2 -silenced lines display hypersensitivity to salinity associated with an altered leaf Na+/K+ ratio, thus confirming that HKT1;2 plays an important role in Na+ homeostasis and salinity tolerance in tomato. Both silenced lines also showed Na + over-accumulation and a slight, but significant, reduction in K+ content in the flower tissues of salt-treated plants and consequently a higher Na+/K+ ratio as compared to the respective unsilenced lines. This altered Na+/K+ ratio in flower tissues is associated with a sharp reduction in fruit yield, measured as total fresh weight and number of fruits, in both silenced lines under salinity conditions. Our findings demonstrate that Na+ transporter HKT1;2 protects the flower against Na+ toxicity and mitigates the reduction in tomato fruit yield under salinity conditions. • Role of SlHKT1;2/ScHKT1;2 in tomato salt tolerance in terms of vegetative growth and fruit yield in a commercial greenhouse. • Two NILs, homozygous for SlHKT1;2 and ScHKT1;2, and their respective Sl/ScHKT1;2 -RNAi-lines were used. • SlHKT1,2 and ScHKT1,2 Na+ transporters prevent Na+ over-accumulation in leaf tissues. • Sl/ScHKT1; 2 Na+ transporters mitigate reductions in fruit yields by reducing floral sodium content. [ABSTRACT FROM AUTHOR]