Paper Title
Genetic Background of Heat Tolerance in Progenies from a Cross Between Tolerant and Sensitive Genotypes in Lolium Perenne

Abstract
Improving tolerance to heat stress is a major challenge in many C3 crops given thethreat of global warming.This study was conducted to examine the genetic basis of variation in heat tolerance of Loliumperenne. The differences in response of genotypes derived from a cross between heat-tolerant (Kangaroo) and heat-sensitive (Norlea) cultivar were examined. There was great association between Fv/Fm and H2O2 content as the value of Fv/Fm decreased gradually with increasing duration of exposure to stress, while the content of H2O2 increased under the stress. Wide genetic distribution was shown among progenies at 40 day of the stress as 72% of the progenies had Fv/Fm values between the two parents, and 67% of the progenies had H2O2 content in the range between the two parents. Most progenies had higher specific leaf area (SLA), thinner leaf and higher leaf density compare to the two parents. These results suggest that the difference in heat tolerance shown by progenies of Loliumperenne is closely associated with the ability to suppress oxidative stress. This genetic distribution indicates the genetic effects and inheritance of the genes responsible for heat tolerance. Leaf traits showed significantly differences among progenies but not between the parents except for leaf water content and leaf thickness. This indicates that the variation in leaf traits is less genetically controlled. Keywords - Chlorophyll Fluorescence, Genetic Background, Heat Stress, Hydrogen Peroxide, Loliumperenne.