Thermotolerance of Commercial Sugarcane Genotypes in Four Phenological Stages.

Six sugarcane genotypes were evaluated for heat tolerance in a field experiment under rain-fed conditions. We studied the response of six commercial sugarcane varieties in four phenological stages to heat tolerance by measuring membrane thermal stability (MTS). This important to understand how commercial varieties of sugarcane respond to this stress in order to maximize productivity. The objective of this study were to measure heat-induced leaf electrolyte leakage in sugarcane genotypes to determine susceptibility to heat in four phenological stages. The research was carried out during 2016 using six commercial varieties (Mex 68-P-23, CP 72-2086, Mex 79-431, RD 75-11, Mex 95-60 and Mex 68-1345) that are commonly grown under rain-fed conditions in southern Tamaulipas Mexico. Heat treatment included 40, 50 and 60°C applied to ten leaf discs during 60 minutes in four phenological stages (vegetative, tillering, beginning of steam elongation, flowering). The experimental design was a randomized complete block with five replications. Analyses of variance were made using the GLM procedure for all variables. Effects associated with variety, phenological stage, heat treatment and the interactions were identified. Electrolyte leakage, estimated as the relative percentage of damage to the cell membrane, was used as criteria for cellular membrane thermotolerance. The results indicated that there were significant differences between varieties, phenological stage and heat treatment. The variety Mex 68-1345 had the highest cell membrane damage (50.2%), while the one with the lowest damage was Mex 68-P-23 (41%); classified as susceptible and heat tolerant respectively. The greatest amount of membrane electrolyte leakage occurred during flowering stage (53%) for the all varieties, but this depends on the heat treatment used. The heat treatment used that induced greatest electrolyte leakage was at 60 °C (72%). The results suggest that in a sugarcane breeding program the heat tolerance selection process could be performed with the membrane thermal stability test with a heat treatment of 60 °C during the stage of higher susceptibility, the flowering.