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Abstract

The quantity and availability of potassium (K) are declining in soils of the world and becoming a serious issue for successful cotton production. Considerable variation for K acquisition has been reported in cotton germplasm. Therefore, exploiting the genotypic variation for K uptake and utilization could be useful for the development of K efficient cultivars. Nine pre-selected cotton cultivars were evaluated for their potassium use efficiency (KUE) and growth response under low (0.26 mM) and adequate (3.33 mM) K levels. Cultivars were grown for six weeks in a hydroponics system supplying with half-strength Hoagland’s solution with the above-mentioned levels of K.Cultivars showed variable response for biomass production, shoot tissue K concentration, K uptake, KUE at low and adequate K levels. Leaves, stalk and root biomass productions were significantly reduced due to low K stress. A significant positive correlation (R2= 0.95**, p<0.01) was found between shoot dry matter (SDM) and KUE at a low K supply level in cotton cultivars. Overall reduction of net photosynthetic rate (PN) in cultivars due to low K stress was 38.7% compared with adequate K level. Furthermore, the correlations of K utilization index and KUEwith the net photosynthetic rate (PN) were positive and highly significant (R2= 0.95**, R2= 0.85**, p<0.01), respectively, at a low K level. Therefore, the potassium utilization efficiency (KUTE) trait can be used as a criterion for the selection of K-efficient cotton cultivars. The results exhibit significant variability for K uptake and KUEin the indigenous cotton cultivars which can be exploited to develop promising cultivars for low K input environments

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