OSMOPRIMING WITH POTASSIUM NITRATE MITIGATES SALINITY STRESS DURING GERMINATION AND EARLY SEEDLING GROWTH OF FIVE BRASSICA GENOTYPES

Abstract

Soil and irrigation-water salinity is one of the principal abiotic constraints on oilseed Brassica production, acting most severely at germination and early seedling establishment. Osmopriming, a controlled pre-sowing hydration treatment, is widely reported to buffer seeds against this early stress window, but its effectiveness varies with genotype and salt intensity. This study evaluated whether priming with a 2% potassium nitrate (KNO3) solution for 24 h could improve germination and seedling growth of five Brassica genotypes (NIFA Gold, UAF-11, Durr-e-Nifa, NIFA-Sarson T-20 and Rachna Canola) across a gradient of simulated soil salinity (0-2% NaCl). A factorial experiment under completely randomized design with three replications was conducted at the University of Agriculture, Faisalabad, recording twelve germination and seedling-growth traits. Analysis of variance showed highly significant (P ≤ 0.01) main effects of genotype and salinity/priming treatment for all twelve traits, and a significant genotype × treatment interaction for eight of them, indicating genotype-specific priming responses. Relative to non-primed seed, KNO3 priming at zero salinity (T1) raised mean germination from 91.1% to 95.6% and seedling vigor index from 970 to 1330, while germination collapsed to 31.1% under the highest salinity level (2% NaCl). Rachna Canola, UAF-11 and NIFA Gold consistently outperformed NIFA-Sarson T-20 across traits, identifying them as comparatively salt-tolerant genetic material. Principal component analysis of the twelve traits across all genotype × treatment combinations showed that a single stress-severity axis explained 80% of total trait variance, confirming that germination capacity and seedling biomass accumulation decline in a coordinated manner under increasing salinity. These findings support KNO3 osmopriming as a low-cost, field-deployable strategy for improving Brassica stand establishment on moderately saline soils, and identify Rachna Canola and UAF-11 as promising parental material for salt-tolerance breeding.