Assessment of salicylic acid and potassium nitrate to mitigate frost stress in autumn-sown potato crop cv. Sutlej

Abstract

Potato is cultivated all the year round in Pakistan. However, the major crop is the autumn crop which is planted in mid-October and contributes 80-85% of the total production. The abrupt climate change has affected the weather patterns all over the world, resulting in the reduction of the mean air temperature in autumn by almost 1.6 °C in Pakistan, which in turn, has adversely affected the crop performance and tuber yield. This trial, therefore, was conducted to optimize and evaluate the concentration of salicylic acid (SA) and potassium nitrate (KNO₃) for inducing frost stress tolerance in an autumn-sown potato crop cv. Sutlej. The findings revealed that the foliar application of 0.5 mM SA significantly enhanced the growth, yield, fluorescent, and biochemical indices of potato plants outperforming 100 mM KNO₃ application in comparison with the control. This included increased plant height by 14% and 17.6%, leaf area index by 6.3% and 26.3%, shoot biomass by 15.4% and 46.2%, crop growth rate by 16.7% and 43.3%, average tuber weight by 8.2% and 23%, tuber diameter by 6.8% and 12.2%, tuber yield by 26.1% and 46.3%, leaf angle by 16.2% and 21.6%, quantum yield of photosystem II by 20.6% and 28.2%, photosynthetically active radiations by 20.5% and 32.4%, chlorophyll content by 6.3% and 14.6%, leaf thickness by 14% and 29%, linear electron flow by 20% and 32.7%, O^-2 by 6% and 14.4%, H₂O₂ by 11.7% and 27.6%, enzyme activities of catalase by 20.7% and 28.5%, superoxide dismutase by 28.6% and 28.5%, peroxidase by 8.3% and 13.5%, ascorbate peroxidase by 17.2% and 37.8%, total protein by 21% and 37%, proline by 36.2% and 114%, and phenolic content by 33% and 63.3% with a reduction in non-photochemical quenching by 12.7% and 29.6%, non-regulatory energy dissipation by 169.5% and 268.5%, and leaf electrolyte leakage by 57.5% and 180%, compared to KNO₃ and the control, respectively. Based on the above findings, it can be concluded and recommended that 0.5 mM foliar spray of SA can be utilized on potato crop cv. Sutlej in frost-sensitive regions. However, the application rate of KNO₃ needs to be optimized in order to use its maximal frost stress tolerance potential.

Keywords: Antioxidative enzymes; Fluorescence-related metrics; Frost stress mitigator; Potassium nitrate; Proline; Reactive oxygen species; Salicylic acid; Tuber yield..

Fig. 1

Maximum and minimum air temperatures recorded for the study area during the experimental duration in 2022–23.

Fig. 2

Comparison of the impact of salicylic acid (SA), potassium nitrate (KNO₃), and a control for plant height and leaf area index (A), shoot biomass and crop growth rate (B), average tuber weight and tuber diameter (C), and tuber yield (D) in potato cv. Sutlej. The bars represent the standard error (±) of the mean (n = 4). Lettering indicates the differences in the treatment means that was conducted through the least significant difference (LSD) test at P ≤ 0.05 after analysis of variance.

Fig. 3

Comparison of the impact of salicylic acid (SA), potassium nitrate (KNO₃), and a control for leaf angle and quantum yield of photosystem II (ΦII) (A), chlorophyll content and photosynthetically active radiation (PAR) (B), non-photochemical quenching (ϕ_NPQ) and non-regulatory energy dissipation (ϕ_NO) (C), and leaf thickness and linear electron flow (D) in the leaves of potato cv. Sutlej. The bars represent the standard error (±) of the mean (n = 4). Lettering indicates the differences in the treatment means that was conducted through the least significant difference (LSD) test at P ≤ 0.05 after analysis of variance.

Fig. 4

Comparison of the impact of salicylic acid (SA), potassium nitrate (KNO₃), and a control for superoxide anion (O–2) and hydrogen peroxide (H₂O₂) (A), catalase (CAT) and superoxide dismutase (SOD) enzyme activities (B), peroxidase (POD) and ascorbate peroxidase (APX) enzyme activities (C), total protein and proline content (D), electrolyte leakage (E), and total phenolic content (F) in the leaves of potato cv. Sutlej. The bars represent the standard error (±) of the mean (n = 4). Lettering indicates the differences in the treatment means that was conducted through the least significant difference (LSD) test at P ≤ 0.05 after analysis of variance.

Fig. 5

Pearson correlation (P ≤ 0.05) among the determined traits of potato cv. Sutlej; PH = plant height, LA = leaf angle, SOD = superoxide dismutase, Φ_II = quantum yield of photosystem II, CAT = catalase, TD = tuber diameter, TY = tuber yield; PAR = photosynthetically active radiation, POD = peroxidase, LEF = linear electron flow; LAI = leaf area index, APX = ascorbate peroxidase, LT = leaf thickness, SB = shoot biomass, ATW = average tuber weight, CGR = crop growth rate, O^–2= superoxide anion, H₂O₂ = hydrogen peroxide content, Φ_NO = non-regulatory energy dissipation, Φ_NPQ = non-photochemical quenching, LEL = leaf electrolyte leakage.

Fig. 6

Appearance of potato plants under the effect of salicylic acid (SA), potassium nitrate (KNO₃) and control after 20 days of frost occurrence.

Fig. 7

The proposed mechanism of frost stress and its tolerance in potato plant.