RELATIONSHIP BETWEEN WATER-RETENTION CAPABILITY AND OSMOTIC ADJUSTMENT IN SORGHUM (SORGHUM-BICOLOR) GROWN UNDER DROUGHT STRESS

Drought resistance of two drought-resistant lines, GP12.1C 1039 and GP .20 Bagdar, and two drought-sensitive lines, GPD11 YSS.89 and GP17.S.3 5, of sorghum was assessed in a pot experiment under glasshouse condit ions. Twenty-eight-day-old plants of these four lines were subjected t o repeated drought cycles for 15 days. The drought-resistant lines wer e superior to the drought-sensitive lines in biomass production and le af area under drought stress. The drought treatment caused a significa nt reduction in leaf osmotic potential in all four lines. A close rela tionship between drought resistance and osmotic adjustment was observe d in these lines differing in drought resistance. For instance, the tw o drought-resistant lines had significantly higher osmotic adjustment (0.469 and 0.496 MPa) than that of the two drought-sensitive lines (0. 428 and 0.310 MPa). By contrast, a negative relationship between droug ht resistance and water retention capability (determined as decrease i n weight of excised leaves during 5-hour drying period) was found in a ll four lines, since the two drought-resistant strains had relatively lower water retention capability than the two drought-sensitive lines. Since there was a negative relationship between water-retention capab ility and osmotic adjustment, water-retention capability cannot be use d as a reliable selection criterion for identification of drought-resi stant genotypes/lines in sorghum.