Effect of heat stress on enzymatic and non-enzymatic antioxidants in Brassica rapa

ABSTRACT

Aim: Heat stress due to increase in global temperature is posing a serious threat to the agricultural sector in many parts of the world. The present investigation was, therefore, undertaken to study the mechanism of thermos-tolerance in four-day-old seedlings of Brassica rapa (44 genotypes) on the basis of various enzymatic and non-enzymatic antioxidants. The information gathered through the present investigation can pave way for imparting tolerance to Brassica genotypes by altering enzyme activities through genetic engineering interventions. Methodology: A total of 44 genotypes were evaluated for survival percentage, electrolyte leakage and chlorophyll content under heat stress conditions. Seedlings were characterized by membrane lipid peroxidation and antioxidants viz. peroxidase and catalase activities, proline and glutathione. Heat stress conditions were created by exposing four-day-old seedlings to 45ºC for 4.5 hr. Out of 44 genotypes, four genotypes (JMT-04-03, TL-2035, TL-98-01 and PBT-37) were thermos-tolerant. Tolerant genotypes registered survival greater than 65%, moderately tolerant between 35-65% and susceptible less than 35%. Results: Among various parameters studied, under heat stress, a significant increase in electrolyte leakage, lipid peroxidation, peroxidase activity, glutathione and proline content was observed in comparison to control seedlings, whereas a decline in CAT activity and chlorophyll content was recorded. Interpretation: Biochemical changes observed in the activities and contents of various parameters studied could be linked with enhanced tolerance to heat stress damage in Brassica rapa which could further be used as a marker for screening against heat stress