Cesium tolerance trait in maize --Magni, A, Nocito, FF, Pilu, R Potassium plays a pivotal role in many biochemical and physiological processes. It has been proposed that higher plants have evolved at least two pathways for root potassium uptake, with high and low-affinity transport properties. Although details on the structure and electrical properties of these transporters are beginning to emerge, many aspects related to their function and regulation need to be investigated further. Selection of mutants modified in potassium transport or potassium homeostasis could be a powerful approach to study these topics. For this purpose we are isolating putative maize mutants tolerant to Cs+, a cytotoxic analogue of potassium which acts as a competitive K+ uptake inhibitor and as a K+ channel blocker.

In a preliminary work we isolated 10 putative monogenic recessive Cs-tolerant mutants by screening several hundred M2 families obtained following chemical (EMS) mutagenesis. Selection was carried out detecting the number of seeds (30 for each experiment) able to germinate and grow in the presence of 100 mM Cs+ (as sulphate) for 10 days. From this initial screening we isolated 10 resistant lines showing a Mendelian segregation ratio expected for a single-gene recessive mutation. These putative Cs-tolerant families were selfed in the last field and the screening of the M3 progenies obtained is now in progress. Preliminary data show that the Cs tolerance trait is maintained at least in two M3 families. Interestingly, one of these putative mutants is able to accumulate more Cs+ than wild-type in the shoot.
 
 


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