Abstract

Cultivation of rice under dry direct sown condition is a viable alternative to reduce the pressure on natural resources, more importantly on available fresh water sources. Moisture stress and intense weed competition are the major limitations under this system for which early seedling vigour is a desirable trait to counter this problem. Laboratory and field experiments were conducted during 2015-16 at S. V. Agricultural College, Tirupati, Andhra Pradesh, India, with 36 aerobic rice genotypes to understand the physiological and biochemical basis for early vigour. High and low vigour genotypes were categorized based on seedling vigour index under polyethylene glycol (PEG) induced moisture stress at -5 and -10 bars. The biochemical basis for high seedling vigour index (SVI) was studied to explore the role of α-amylase in rapid conversion of starch into reducing sugars in high vigour genotypes. Laboratory findings were confirmed in the field experiment where in early vigour genotypes (NLR-33671, NLR-3042, NLR-4002, NLR-40024, MTU-7029, MTU-1010, JGL20171 and JGL-11727) showed high crop growth rate in pre-anthesis period of crop growth. The influence of early vegetative biomass was also reflected on number of tillers and number of productive tillers in high vigorous genotypes compared to low vigorous genotypes (MTU1075 and MTU-1112).