Improving the Biocontrol Potential of Endophytic Bacteria Bacillus subtilis with Salicylic Acid against Phytophthora infestans-Caused Postharvest Potato Tuber Late Blight and Impact on Stored Tubers Quality

Abstract

Potato (Solanum tuberosum L.) tubers are a highly important food crop in many countries due to their nutritional value and health-promoting properties. Postharvest disease caused by Phytophthora infestans leads to the significant decay of stored potatoes. The main objective of this study was to evaluate the effects of the endophytic bacteria, Bacillus subtilis (strain 10–4), or its combination with salicylic acid (SA), on some resistance and quality traits of stored Ph. infestans-infected potato tubers. The experiments were conducted using hydroponically grown potato mini-tubers, infected prior to storage with Ph. infestans, and then coated with B. subtilis, alone and in combination with SA, which were then stored for six months. The results revealed that infection with Ph. infestans significantly increased tuber late blight incidence (up to 90–100%) and oxidative and osmotic damage (i.e., malondialdehyde and proline) in tubers. These phenomena were accompanied by a decrease in starch, reducing sugars (RS), and total dry matter (TDM) contents and an increase in amylase (AMY) activity. Moreover, total glycoalkaloids (GA) (α-solanine, α-chaconine) notably increased in infected tubers, exceeding (by 1.6 times) permissible safe levels (200 mg/kg FW). Treatments with B. subtilis or its combination with SA decreased Ph. infestans-activated tuber late blight incidence (by 30–40%) and reduced oxidative and osmotic damages (i.e., malondialdehyde and proline) and AMY activity in stored, infected tubers. Additionally, these treatments decreased pathogen-activated GA accumulation and increased ascorbic acid in stored tubers. Thus, the results indicated that endophytic bacteria B. subtilis, individually, and especially in combination with SA, have the potential to increase potato postharvest resistance to late blight and improve tuber quality in long-term storage.

Advances in the Modulation of Potato Tuber Dormancy and Sprouting

“…The administration of SA to potatoes can alter the duration of dormancy by interacting with a range of physiological pathways. SA has been reported to extend the dormancy period of potato tubers by reducing starch breakdown and increasing glycoalkaloid levels [133]. This results in delayed sprouting and growth, which is beneficial to potato storage and shelf life.…”

Plant growth-promoting bacteria potentiate antifungal and plant-beneficial responses of Trichoderma atroviride by upregulating its effector functions

“…For example, Pseudomonas fluorescens G20-18 induces salicylic acid-mediated defense in A. thaliana protecting the plant against Pseudomonas syringae [31] and promoting growth in cabbage plants [32,33]. Meanwhile, Bacillus subtilis induces resistance in potato plants against Phytophthora infestans [34], Bacillus vallismortis has antagonistic activity against the fungus Macrophomina phaseolina [35], and Bacillus velezensis VRU1 capsule formulation was shown to be effective against Rhizoctonia solani and protection against this pathogen [36]. Consortia formed with Bacillus halotolerans strains promoted A. thaliana and tomato growth and root system development and enhanced protection against Botrytis cinerea [37].…”

Endophytic Bacillus subtilis H17‐16 effectively inhibits Phytophthora infestans, the pathogen of potato late blight, and its potential application

“…Biological control mainly uses beneficial microorganism and some bioactive substances to control diseases, which has the advantages of environmental friendliness and sustainability 13 . Bacillus , Pseudomonas , Streptomyces and Trichoderma were the main reported biocontrol microorganisms to have inhibitory effects on Phytophthora infestans 14–17 . Commercial products of Trichoderma and Bacillus have been applied to control potato late blight 13,18 .…”

“…13 Bacillus, Pseudomonas, Streptomyces and Trichoderma were the main reported biocontrol microorganisms to have inhibitory effects on Phytophthora infestans. [14][15][16][17] Commercial products of Trichoderma and Bacillus have been applied to control potato late blight. 13,18 However, although there has been some progress in the application of biocontrol microorganism, the effect of disease control is often not as good as that of chemical agents.…”