European Journal of Sustainable Agroecosystems

Background: Cotton is an important fiber crop in the world and its yield is affected by the occurrence of constant drought due to climate change. Cotton is usually grown in rainfed or watered lands, thus making it very important to look for varieties that can give high yield in drought situations. Key indicators needed for identification of drought-tolerant cultivars are drought tolerance indices based on performance and morphological characteristics. 
Objective: This review would analyze peer-reviewed publications on screening upland cotton cultivars for drought tolerance using the drought tolerance indices in order to summarize the methods, compare the results, and highlight the gaps in research.
Literature sources: A systematic search was performed through Scopus, Web of Science, PubMed/PMC, Google Scholar, ScienceDirect, SpringerLink and grey literature from FAO and ICAC for the period from 2015 to 2025 with additional references from the established methodology before this period. 
Main findings: Stress susceptibility index (SSI), Index of stress tolerance (STI), Geometric mean productivity (GMP), Mean productivity (MP) and Yield index (YI) are identified as the most commonly used indices and mutually harmonizing indices based on their high efficiency, with STI, GMP and MP proving to be the best choices concerning genotype characterization regarding high yield and stress resistance. Seedling-level morphological traits (root length, root volume, relative water content) and biochemical markers (proline, malondialdehyde, antioxygenic enzymes) show significant correlation with the tolerance coefficients obtained in field conditions, providing a rationale for utilizing multiple indices for selecting and statistical analyzing the data through principal component and cluster analysis. Research gaps: Unresolved issues include the lack of multi-season and multi-environment validation of indices, inconsistency between indices chosen in research, an insufficient use of genomic and high-throughput phenotype techniques and weak combination of molecular markers with indices evaluation.
Summary: The integration of traditional yield-based metrics, along with physiological, biochemical and molecular markers in multi-environment trials, provides the best approach for identifying drought-resistant cotton genotypes, and future research should focus on standardized, reproducible, genomics-based screening methods.