RESUMO
Seventy-one genotypes of sugarcane from diverse agro-climatic zones of India viz. peninsular, northwest, north-central and eastern zones, were screened for their tolerance to high temperature stress based on the damage to leaf biomass i.e. necrosis of leaf-tips and margins, and rolling of leaves. Nine selected genotypes showing variable response to heat injury were tested for activity pattern of isoforms of two H2O2-scavenging enzymes; ascorbate peroxidase (APX) and catalase (CAT), under high temperature induced oxidative stress. Changes in the activity of APX and CAT isozymes in leaves corresponded to the level of tolerance of genotypes towards heat injury which was substantiated by the highly negative correlation coefficients of heat injury levels of leaves vs. integrated density of APX and CAT isozyme bands. This indicated that the criteria of higher expression of CATs’ and APXs’, the two major reactive oxygen species scavenging proteins in leaves may be used to screen large seedling populations and germplasm for high temperature tolerance.