Thermal stress evaluation of suspension cell cultures in winter wheat

The objectives of this study were to compare thermotolerance in whole plants vs. suspension cell cultures of winter wheat, and to evaluate the synthesis of heat shock proteins in relation to genotypic differences in thermotolerance in suspension cells. Whole plant genetic differences in the development of heat tolerance were identified for three wheat genotypes (ND 7532, KS 75210 and TAM 101). Suspension cell cultures of these genotypes were used to evaluatein vitro response to heat stress. Viability tests by triphenyl tetrazolium chloride (TTC) and by fluorescein diacetate (FD) were utilized to determine the relationship of cellular response to heat stress (37°C/24 h, 50°C/1h). KS 75210 and ND 7532 are relatively heat susceptible. TAM 101 is heat tolerant. Both tests at the cellular level were similar to the whole plant response. Thus, cellular selection for enhancing heat tolerance seems feasible. Heat shock protein (HSP) synthesis of two genotypes, ND 7532 and TAM 101 were determined for suspension cultured cells. In suspension cultures, HSPs of molecular weight 16 and 17 kD were found to be synthesized at higher levels in the heat tolerant genotype (TAM 101) than the susceptible genotype (ND 7532), both at 34° and 37°C treatments for 2 hours and 5 hours. HSP 22 kD was synthesized more at 34°C for TAM 101 than ND 7532, but not at 37°C; whereas, HSP 33 kD was synthesized at 37°C at similar abundance for both genotypes, but not at 34°C.These results indicated that there is a differential expression of HSP genes in wheat suspension cells at different temperature stress durations and between heat tolerant and heat susceptible genotypes. It appears that the levels of synthesis of HSPs 16 and 17 kD are correlated with genotypic differences in thermal tolerance at the cellular level in two genotypes of wheat.