Effect of KNO3‐Priming on Agronomic, Physicochemical and Fibre Attributes of Cotton (Gossypium hirsutum L.) Under Saline Conditions

Abstract

ABSTRACTSalinity stress presents a challenging dilemma for plant growth and development. It disrupts cotton (Gossypium hirsutum L.) yield through an immediate osmotic and a slower ionic phase, ultimately diminishing its fibre quality. Seed priming, a low‐cost seed pre‐treatment, mitigates these effects by triggering prior metabolic processes and subsequent gene expression. This pioneering work aimed to improve agronomic, physicochemical parameters and fibre characteristics in cotton genotypes (GH‐Baghdadi and GH‐Mubarak) by potassium nitrate (KNO3) mediated osmopriming (1.25% and 1.5% conc.) for 15, 20 and 25 h, along with an un‐primed control under saline field conditions. The randomised complete block design experiment in triplicate was conducted in 2019 and 2020 at the soil with electrical conductivity (extract) (ECe) 9.44 dS m−1 to investigate optimal priming media and priming duration. The results showed that salinity impaired physicochemical and agronomic parameters in the control experiment. However, seed priming with 1.5% KNO3 for 20 h significantly improved the yield and yield contributing components in both genotypes. Maximum values for chlorophyll (Chl) a and b were recorded at 1.50 and 0.90 mg g−1 fresh weight (FW), respectively, under this treatment. Similarly, the chlorophyll‐a fluorescence parameters (Chl‐a FPs), such as the maximum quantum yield of photosystem II (Fv/Fm ) (0.83), effective quantum yield of PSII (ΦPSII) (0.76) and photochemical quenching coefficient (qP) (0.85), indicated improved light harvesting, electron transport and photosynthetic capacity. Furthermore, the net photosynthetic rate (Pn) increased to 19.65 mmol CO2 m−2 s−1, while stomatal conductance (gs) reached 28.39 mmol CO2 m−2 s−1 at the same treatment. A strongly positive correlation was found between chl‐a FPs and net photosynthetic yield. Enzymatic activities, including catalase (CAT) at 2.17 unit mg−1, superoxide dismutase (SOD) at 1.05 unit mg−1 and peroxidase (POD) at 1.50 unit mg−1 were significantly enhanced, along with leaf potassium (K) (14.3 mg g−1 dry weight [DW]) and calcium (Ca) (6.7 mg g−1 DW), particularly in GH‐Mubarak. Seed‐cotton yield (SCY) increased to 5274 kg h−1 and fibre strength (FS) improved to 31.3 thousand pounds per square inch (tppsi), while ginning out‐turn (GOT) reached a maximum of 45% at 1.5% KNO3 for 20 h in both genotypes. The micronaire value (4 μg in.−2) significantly decreased, indicating improved fibre fineness. Correlation analysis revealed a strong positive correlation between physicochemical and agronomic traits, particularly gas exchange characteristics, chlorophyll content and Chl‐a FPs, which are strongly associated with SCY and fibre characteristics. In conclusion, priming cotton seeds with 1.5% KNO3 for 20 h is a promising strategy for mitigating salinity stress and enhancing physicochemical attributes and agronomic traits, ultimately leading to improved cotton yield and fibre quality.