Phenotyping of Thermotolerant Finger Millet (Eleusine coracana L.) Genotypes using Temperature Induction Response at the Seedling Stage
Abstract
The Temperature Induction Response (TIR) technique was standardized and employed to identify thermotolerant finger millet (Eleusine coracana L.) genotypes at the seedling stage. The technique involves exposing seedlings to a gradual sub-lethal temperature induction followed by a lethal temperature treatment, and subsequently assessing seedling recovery. Optimization of induction and lethal temperature regimes was based on percent seedling survival and percent reduction in root and shoot growth after a 72-hrecovery period. An induction treatment ranging from 37°C to 52°C over five hours, followed by exposure to a lethal temperature of 58°C for two hours, was identified as optimal for screening. Fifteen finger millet genotypes were evaluated under induced and non-induced conditions. Genotypes were classified based on seedling survival percentage and growth reduction parameters. Cultivar Tirumala and genotype VR-1099 exhibited the least reduction in root and shoot growth along with higher survival rates, indicating superior thermotolerance. The study demonstrates that the TIR technique is an effective and rapid phenotyping tool for identifying thermotolerant finger millet genotypes at the seedling stage, facilitating the efficient selection of parental lines for breeding heat-resilient varieties.
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Introduction
High temperature stress is a major abiotic constraint affecting crop productivity, particularly in semi-arid and tropical regions. Plants exhibit both inherent (basal) thermotolerance and acquired thermotolerance, the latter being rapidly induced by prior exposure to moderately high temperatures. The Temperature Induction Response (TIR) technique was developed to exploit this adaptive mechanism by subjecting seedlings to sub-lethal temperature stress prior to lethal temperature exposure, thereby enabling the identification of genotypes with superior heat tolerance. Acquired thermotolerance is associated with cellular acclimation processes, including the synthesis and accumulation of heat shock proteins (HSPs), which function as molecular chaperones that maintain protein stability under stress conditions. Previous studies have demonstrated that seedlings exposed to induction temperatures prior to lethal stress show enhanced survival and recovery compared to directly stressed seedlings. Therefore, standardization of induction and lethal temperature regimes is crucial for accurately screening genotypes for intrinsic heat tolerance. Given the increasing frequency of heat stress episodes under climate change scenarios, identifying crops with enhanced thermotolerance is essential for sustainable crop improvement programs. Finger millet, a nutrient-dense, climate-resilient cereal crucial for food security in arid regions, is a prime candidate for such thermotolerance screening. The objectives of this study were to (1) standardize the TIR protocol for finger millet seedlings, and (2) employ this protocol to screen and classify fifteen genotypes for thermotolerance. Website: www.ijoear.com Journal DOI: 10.25125/agriculture-journal
Conclusion
The Temperature Induction Response (TIR) technique proved to be an effective and rapid method for screening finger millet (Eleusine coracana L.) genotypes for thermotolerance at the seedling stage. Significant genotypic variation was observed for root and shoot growth reduction and seedling survival under high temperature stress. Cultivar Tirumala and genotype VR 1099 exhibited minimal growth reduction and higher survival, indicating superior thermotolerance, whereas PPR 1216 and PPR 1094 were identified as susceptible. The study confirms the usefulness of TIR-based phenotyping for early-stage selection of heat-tolerant genotypes. The identified thermotolerant genotypes are recommended for use as donor parents in hybridization programs and for further validation under field-level heat stress conditions to develop climate-resilient finger millet varieties CONFLICT OF INTEREST The authors declare no conflict of interest. Website: www.ijoear.com Journal DOI: 10.25125/agriculture-journal
