Increased Fe-toxicity tolerance in rice calli and modulation in isozyme profiles

Abstract

Seed derived calli of rice cultivars, ‘IR72’ (susceptible) and ‘C14-8’ (tolerant) were screened <i style="">in vitro</i> under increasing levels (50, 100, 200 or 400 ppm) of Fe-toxicity and profiled for isozymes, viz. esterase, peroxidase, malate dehydrogenase and lactate dehydrogenase, to assess their involvement in Fe-toxicity tolerance. <i style="">In vitro</i> screening showed the detrimental effect of hifher concentration on plantlet regeneration. However, a few calli survived on stressed medium and regenerated plantlets. Cultivar ‘C14-8’ showed higher degree of tolerance than ‘IR72’. Prominent differences including changes in band activity/intensity, mobility/shift and number of polymorphic loci with respect of Fe-toxicity were evident. The activity of esterase, malate dehydrogenase and lactate dehydrogenase decreased in Fe-stressed medium in ‘C14-8’. Decreased activity indicates gradual degradation of these enzymes or their structural modification under increased Fe-toxicity levels. On the other hand, the activity of these enzymes increased in the ‘IR72’ under stressed medium. However, the activity of peroxidase remained almost unaltered in ‘C14-8’ across the stress gradient. Few bands disappeared or newly appeared in the stressed medium as compared to control. This may be due to activation or inactivation of diverse domains in the genome and may be involved in governing Fe-toxicity tolerance. Whereas, a few bands remained unaltered across the stress gradient, and these may be used as biochemical marker for selection of tolerant plants against iron toxicity.