Integrated stress indices, GGE biplot and physiological approaches reveal superior pre-released genotypes of linseed (Linum usitatissimum L.) for drought tolerance at reproductive stage

The present investigation was undertaken to assess genetic variability and identify the drought tolerant pre-released genotypes of linseed. Forty-two genotypes were evaluated under irrigated and managed drought stress conditions across the two years, followed by multi-location validation of selected genotypes under field and rainout shelter using GGE biplot approach. Further, validation was performed through root system architecture (RSA), leaf physiology, histo-chemical staining and DNA fingerprinting using EST marker was done for its exploitation in breeding programmes. Moreover, EST-derived markers provided a targeted assessment of genetic diversity and should be interpreted as a proof-of-concept. The significant genetic variability was observed for yield and key morphological traits. Traits such as plant height, number of branches per plant, number of capsules per plant, biological yield per plant, relative water content, membrane stability index and chlorophyll content were identified as reliable morphological traits under drought stress. Among stress indices, stress tolerance index, harmonic mean and yield index were proved as most effective for identifying high yielding genotypes with enhanced drought tolerance, resulting six genotypes were found drought tolerant. Among them two genotypes i.e. G32 (BLS 2022-28) and G28 (BLS 2022-24) exhibited superior yield and stability over the environments. Based on multi-environments validation, these two genotypes were confirmed as drought tolerant, supported by robust RSA and their relative ability to limit ROS accumulation. The DNA fingerprinting of selected genotypes showed the significant diversity among the reference panel of linseed, indicating their potential for targeted genotype fingerprinting and locus specific diversity assessment. These genotypes have strong potential for including in drought resilient linseed breeding programs.