Contact email- 22114944@student.westernsydney.edu.au, J.Bose@westernsydney.edu.au

Wheat is the major cereal crop providing 20% of global dietary energy and protein intake. Rapidly increasing human population demands a doubling of wheat production by 2050. However, arable lands are becoming increasingly saline and posing a major threat to wheat production by causing up to 60 per cent yield reduction. Hence, improving wheat salt tolerance is critical to ensure global food security.

Salt exclusion from the photosynthetic tissue has been considered a common salt-tolerant mechanism in wheat, however, some genotypes showed higher salt accumulation while maintaining comparable photosynthetic performance. This observation led us to test how salt loads are managed within the mesophyll cells, in particular vacuole and chloroplasts of contrasting wheat genotypes. We treated nine genotypes of Triticum aestivum with AABBDD genome, and its relatives T. durum with AABB, T. monococum with AA, Aegilos tauschii with DD genomes to 150mM NaCl stress and observed their leaf tissue tolerance.

We measured chlorophyll content, photosynthetic rate, stomatal conductance and chlorophyll fluorescence parameters such as Fv/Fm ratio, PhiNO and PhiPSII up to three weeks of salt treatment from the fourth leaf. Sodium and potassium accumulation in leaves after three weeks of salt treatment was quantified using ICP-OES. Vacuolar and chloroplast Na accumulation within leaf mesophyll cells were quantified using the Na-selective fluorescent dye CoroNa green.

We also measured the gene expression of key transporters implicated in vacuolar sequestration (NHX), and chloroplast ion homeostasis (MSL2/3, BASS2, KEA1) to understand the molecular mechanism involved in leaf tissue tolerance. Our results suggested that controlling Na accumulation within the mesophyll chloroplasts through regulated expression of transport proteins is a key determinant to maintaining photosynthetic function during salt stress.