Evaluation of the usefulness of senescing agent potassium iodide for assessing inter-cultivar variation for drought tolerance in pearl millet [Pennisetum glaucum (L.) R.Br.]

Abstract

Drought stress is an important limitation to the growth and grain yield of pearl millet in arid and semi-arid regions of the world. Potassium iodide, a senescing agent, was used as a screening tool for evaluating drought tolerance of 22 strains of pearl millet at the grain development stage (grain filling) under glasshouse conditions. In order to use potassium iodide as a selection method in breeding programs for improvement of drought tolerance, the technique was compared with some drought evaluating parameters such as water retention capability, osmotic adjustment, photosynthetic capacity and water-use efficiency. Application of a 0.3% solution of potassium iodide at anthesis was very effective in causing drought stress, and hence grain yield reduction, in pearl millet. It showed a significant association with water deficit in growth attributes such as fresh and dry weights of shoots, and grain yield. Osmotic adjustment, water retention capability (decrease in weight of excised leaves during 5-h drying period), photosynthetic rate, and single-leaf water-use efficiency (net CO₂ assimilation rate/transpiration) did not show positive relationships with the degree of drought tolerance measured using potassium iodide spray or water-deficit treatment. A large amount of variation in drought tolerance observed in 22 lines of pearl millet can be of considerable practical value. For example, the 3 lines ICMP-83720, ICMV-9413 and ICMV-94472, ranked as highly drought tolerant on the basis of their overall growth and physiological performance, and could be of direct use under mild drought conditions.