T. Raghavendra, K. Mohan Vishnuvardhan, B. Ravi Prakash Reddy, P. Lakshmi Kalyani and P. Umamaheswari Department of Crop Physiology,
Abstract
Cotton has global importance, being a major fiber crop with a high commercial value. It is grown in tropical and sub-tropical regions and plays pivotal role in economy in many countries. It thrives well under optimal temperature. Too high and too low temperatures affect badly its growth and yield. Too low temperature affects its germination and seedling establishment stages. Particularly, high temperatures influence many physiological and biochemical processes within cotton plant that result in poor seed cotton yield. Plants, when exposed to sub-lethal stress (induction stress), develop the ability to withstand severe temperatures and this phenomenon is often referred to as acquired thermo tolerance. In this context, a lab experiment was conducted to standardize the temperature induction response (TIR) protocol for cotton seedlings using WGC-450 programmable plant growth chamber. Temperatures were standardized as sub lethal, i.e. challenging temperatures as 28-40 0C (for 4 hours) and lethal temperatures as 47 0C (for 3 hours). A set of diverse cotton germplasm comprising of 35 genotypes were screened for intrinsic tolerance using the standardized Thermo Induced Response (TIR) protocol. Among the genotypes CNH-09-073, BGDS-1077, NDLH-2057-1, ARBH-1851, ABD-645, RAH-1075 and NDLH 2028-2 showed highest thermo tolerance in terms of higher seedling survival with no reduction in root and shoot growth.