How Deficit Irrigation and Salicylic Acid Treatments Affect Plant Growth and Fruit Production in Summer-Fall Production of 'San Andreas' Strawberry

Abstract

Drought is one of the most important environmental stresses that threaten plant growth and development, fruit yield, and the quality of strawberries. Applying biological regulators such as salicylic acid (SA) effectively reduces the negative effects of water-deficit stress and improves the growth and yield performance of strawberries. This study aimed to determine the impact of irrigation levels and salicylic acid on morphological, physiological, yield, and quality parameters of day-neutral strawberry cv. 'San Andreas.' The strawberry plants were planted in black pots containing a soil, peat, and perlite mixture (2:1:1). An equal amount of irrigation water was maintained for the plants after planting until they had 3-4 leaves. Three irrigation levels were applied at 100% (I100), 80% (I80), and 60% (I60) of the field capacity. Foliar salicylic acid at concentrations of 0 (control), 1, and 2 mM were applied three times, commencing at 2-week intervals, after applying the irrigation levels. Decreasing irrigation levels significantly reduced the number of inflorescences, runners, and crowns as well as root length, number of leaves, total leaf area, and plant fresh and dry weights. Decreasing irrigation levels caused an increase in leaf temperature, chlorophyll content, proline and malondialdehyde content (MDA), and a decrease in the relative water content in leaves of the 'San Andreas' cultivar. Decreasing irrigation levels also decreased the total yield and average fruit weight while they increased fruit quality factors such as fruit firmness, soluble solids content (SSC), and titratable acid content. Salicylic acid applications alleviated some negative effects of drought stress by increasing chlorophyll and proline content and decreasing MDA content. Additionally, salicylic acid application significantly increased total yield (1 mM), fruit weight (1 mM), and fruit quality parameters (SSC and titratable acid content [1 mM]). These results suggest that decreasing irrigation levels significantly limited plant growth and yield in the summer-fall production of the 'San Andreas' day-neutral strawberry cultivar. At the same time, SA applications improved yield and fruit quality. These findings provide valuable insight into the mechanisms underlying drought stress tolerance in strawberries and highlight the potential of salicylic acid as a tool to improve strawberry production under limited water conditions.