Use of compact and friable callus cultures to study adaptive morphological and biochemical responses of potato (Solanum tuberosum) to iron supply

•Effect of Fe nutrition on callus morphology is dependent on callus type and culture duration.•Fe nutrition influenced levels of photosynthetic pigments in potato calli.•Friable and compact callus cultures exhibit differential tolerance to chlorosis.•Fe deficiency enhanced ferric reduction capacity and phenolic production.•Antioxidant enzyme activity is lowered in response to Fe deficiency.

The efficient utilization, storage and buffering of iron (Fe) is necessary to prevent the development of iron deficiency or toxicity related stresses in plants. It is of practical interest to develop effective in vitro plant tissue culture schemes for generating chlorosis-tolerant and/or Fe-biofortified plants. The objectives of this study were to induce the formation of compact and friable calli from leaf explants of potato and to investigate adaptive responses to Fe nutrition using these in vitro cell culture-based systems. The severity of chlorosis of the callus cultures increased with the withdrawal of Fe supplementation from the growth medium and the culture duration. Ferric chelate reductase (FCR) activity was found to be higher in the compact compared to the friable potato callus cultures. Chlorophyll and carotenoids content in compact calli increased with an increase in Fe supply but in friable calli carotenoids content declined and the chlorophyll level was unaffected. Phenolic content in Fe-deficient compact calli was significantly higher than in friable ones but a reverse trend was observed as the culture period was extended. Peroxidase activity was reduced in both compact and friable calli cultured under Fe-deprived condition compared to those on Fe-sufficient medium. Friable and compact calli displayed differential morphological and biochemical responses to Fe deficiency. These calli also appeared to vary in their sensitivity to Fe-deficiency and the response to Fe nutrition seemed to be related to the culture duration.