GENETIC VARIABILITY IN A HETEROGENEOUS POPULATION OF BARLEY (HORDEUM VULGARE)

Two populations, dryland (D) and irrigated (I), were developed by propagating Composite Cross XXI (CCXXI) of barley (Hordeum vulgare L.) under contrasting soil moisture levels. Both populations were characterized by low outcrossing rates (less than 1%) and high levels of genetic variability. The means of these two populations did not show much divergence for six quantitative characters. However, substantially greater variability was observed in the D population for grain size and yield. Exposure to greater fluctuations of soil moisture and reduced intergenotype competition under dryland conditions were considered responsible for maintaining greater variability in the D population. The results indicated that continuous propagation of heterogeneous populations such as composite crosses of barley under low rainfall (average annual precipitation of about 350 mm) conditions is more effective in reducing genetic erosion and maintaining agriculturally useful variability than under more favorable rainfed conditions.