Comparative Analyses of Four Chemicals Used to Control Black Mold Disease in Tomato and Its Effects on Defense Signaling Pathways, Productivity and Quality Traits
Genetics and Genetic Engineering Dept., Faculty of Agriculture, Benha University, Qalyubia 13736, Egypt
Postharvest Diseases Dept., Plant Pathology Research Institute, ARC, Giza 12619, Egypt
Horticulture Dept., Faculty of Agriculture, Benha University, Qalyubia 13736, Egypt
Department of Biology, Faculty of Applied Sciences, Umm Al-Qura University, Makkah 21955, Saudi Arabia
Research Laboratories Center, Faculty of Applied Science, Umm Al-Qura University, Makkah 21955, Saudi Arabia
Agricultural Genetic Engineering Research Institute (AGERI), ARC, Giza 12619, Egypt
Author to whom correspondence should be addressed.
Plants 2020, 9(7), 808; https://doi.org/10.3390/plants9070808
Received: 4 April 2020 / Revised: 16 June 2020 / Accepted: 22 June 2020 / Published: 28 June 2020
(This article belongs to the Special Issue Plant-Fungal Pathogen Interaction)
The field application of safe chemical inducers plays a vital role in the stimulation of systematic acquired resistance (SAR) of plants. In this study, the efficacy use of three and six field applications with chitosan, lithovit, and K-thiosulfate at 4 g L−1 and salicylic acid at 1.5 g L−1 in improving tomato productivity, quality, and modifying the defense signaling pathways to the Alternaria alternata infection was investigated. Salicylic acid was the most effective in vitro where it completely inhibited the growth of Alternaria alternata. The highest yield quantity was recorded with six applications with Chitosan followed by Salicylic acid; also, they were the most effective treatments in controlling the Alternaria alternata infection in tomato fruits. The maximum increase in chitinase and catalase activity of tomato fruits was observed at five days after inoculation, following treatment with six sprays of salicylic acid followed by chitosan. The transcript levels of seven defense-related genes: ethylene-responsive transcription factor 3 (RAP), xyloglucan endotransglucosylase 2 (XET-2), catalytic hydrolase -2 (ACS-2), proteinase inhibitor II (PINII), phenylalanine ammonia-lyase 5 (PAL5), lipoxygenase D (LOXD), and pathogenesis-related protein 1 (PR1) were upregulated in response to all treatments. The highest expression levels of the seven studied genes were recorded in response to six foliar applications with chitosan. Chitosan followed by salicylic acid was the most effective among the tested elicitors in controlling the black mold rot in tomato fruits. In conclusion, pre-harvest chitosan and salicylic acid in vivo application with six sprays could be recommended as effective safe alternatives to fungicides against black mold disease in tomato fruits.