Standardization of optimal concentration of PEG-6000 for induction of moisture stress in coriander genotypes

Abstract

Coriander (Coriandrum sativum) is an important seed spice and leafy herb valued for its aromatic seeds, flavorful leaves and medicinal properties. Despite its economic significance, coriander is highly sensitive to drought, particularly during germination and early seedling growth, which can adversely affect establishment, growth, yield and seed quality. In the context of climate change and increasing water scarcity, developing drought-tolerant coriander varieties is essential. This study aimed to standardize polyethylene glycol (PEG-6000)-induced osmotic stress for in vitro screening of coriander genotypes. Laboratory experiments were conducted using coriander variety Varadevi-2, exposing seeds to graded PEG-6000 concentrations (0, 5, 10, 15, 20, and 25%) in a Completely Randomized Design with four replications. Germination percentage, seedling growth parameters, and seedling vigour index were recorded, and probit analysis was used to determine the concentration causing 50% reduction in germination (GR₅₀). Results indicated a clear concentration-dependent decline in germination and seedling performance. Germination decreased from 70% under control to 34% at 10% PEG and reached only 1% at 25% PEG. Shoot and seedling length, root length, and vigour index followed similar declining trends, with moderate enhancement of root length at 10% PEG, suggesting adaptive responses. Probit analysis identified 10% PEG as the GR₅₀, representing an optimal, sub-lethal stress level capable of differentiating tolerant and susceptible genotypes. In conclusion, 10% PEG-6000 was standardized as the optimal osmotic stress for in vitro screening of coriander, providing a reliable and reproducible method for identifying drought-tolerant genotypes, which can be utilized in breeding programs to develop resilient varieties under water-limited conditions.