Screening lentil genotypes for chromium resilience: A study of growth characteristics, oxidative stress responses, and expression analysis

Abstract

Plants face environmental challenges from the deposition of heavy metals in soil that hinder growth and compromise yield. Despite the significant losses caused by chromium (Cr) stress, the development of efficient screening methods, as well as the identification of tolerant lentil germplasm and resistance genes remains inadequate. To tackle this, we screened 200 lentil genotypes for Cr tolerance at the seedling stage using a completely randomized block design with three replications under hydroponic condition. The results showed significant genetic diversity among the genotypes, with reductions in morphological traits under Cr stress ranging from 5.66 % for relative water (RW) content to 58.14 % for fresh shoot (FS) weight compared to controls. Principal component analysis identified four key traits contributing to stress tolerance: fresh shoot (FS) weight (0.0657 g), dry shoot (DS) weight (0.0084 g), shoot length (SL) (8.9315 cm), and dry root (DR) weight (0.0084 g). These traits were positively correlated with each other and can serve as selection criteria for identifying elite tolerant genotypes. Genotypes were clustered into four groups, and five Cr-tolerant genotypes were selected based on a stress tolerance index (STI) value of > 0.65 for all studied traits. These selected genotypes exhibited efficient antioxidant activities, indicating inherent defense mechanisms. Antioxidant enzyme levels increased significantly, except for ascorbate peroxidase (APX), which decreased compared to controls. Under Cr stress, osmolyte and antioxidant enzyme accumulation increased, while total protein and flavonoid content decreased. Cr toxicity is believed to induce oxidative damage, as evidenced by elevated antioxidant enzyme levels and reduced photosynthetic pigments. RNA-seq data analysis revealed five Cr stress tolerance genes, which were further validated through RT-qPCR. These findings suggest that the five genotypes identified could serve as potential lines for developing Cr-tolerant lentils. Additionally, the roles of five Cr stress tolerance genes warrant further investigation to better understand their functional mechanisms under Cr stress in lentils.