Unravelling the synergistic interaction of Thrips tabaci and newly recorded, Thrips parvispinus with Alternaria porri (Ellis.) Cif., inciting onion purple blotch

Authors: SAINI, SHUBHAM - Haryana Agricultural University; RAJ, KUSHAL - Haryana Agricultural University; SAINI, ANIL KUMAR - Haryana Agricultural University; KUMAR, RAKESH - Haryana Agricultural University; SAINI, ANKIT - Haryana Agricultural University; KHAN, ASLAM - Haryana Agricultural University; KUMAR, PANKAJ - Haryana Agricultural University; DEVI, GEETA - Haryana Agricultural University; BHAMBHU, MUKUL KUMAR - Haryana Agricultural University; McKenzie, Cindy; LAL, MAKHAN - Haryana Agricultural University; WATI, LEELA - Haryana Agricultural University

Submitted to: Frontiers in Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/13/2024
Publication Date: 3/5/2024
Citation: Saini, S., Raj, K., Saini, A., Kumar, R., Saini, A., Khan, A., Kumar, P., Devi, G., Bhambhu, M., Mckenzie, C.L., Lal, M., Wati, L. 2024. Unravelling the synergistic interaction of Thrips tabaci and newly recorded, Thrips parvispinus with Alternaria porri (Ellis.) Cif., inciting onion purple blotch. Frontiers in Microbiology. 15. Article 1321921. https://doi.org/10.3389/fmicb.2024.1321921.
DOI: https://doi.org/10.3389/fmicb.2024.1321921

Interpretive Summary: Thrips pose a significant threat to agricultural and horticultural crop production worldwide due their abrasive feeding damage and ability to transmit plant pathogens including many viruses. Thrips are often found in onion fields concurrently with many different fungal pathogens including purple blotch disease. We found that when plants were injured by thrips, purple blotch disease was greatly enhanced both in incidence and severity. In addition, onion leaves were shorter and had less leaf area than onions that were not infected with purple blotch. When thrips damage was present, lesion number, length and size was greatly enhanced. Alternaria porri combined with injury caused a more pronounced decrease in total soluble sugars and total protein content but enhanced the total phenolics and hydrogen peroxide content compared to uninjured plants. Controlling thrips in onion production should help to reduce the severity and incidence of purple blotch disease resulting in higher crop yields with better quality onions.

Technical Abstract: Onion purple blotch is the most devastating foliar disease of onions and has become a major concern for farmers and researchers in onion growing regions of India. Investigations to determine the role of insect damage and disease incidence of Alternaria porri indicated that disease incidence and severity enhance considerably with injury. Thrips injured plants inoculated with Alternaria porri presented 100% incidence and 52-72% severity while mechanically injured plants inoculated with Alternaria porri showed 60-70% incidence and 28-34% per cent severity. The uninjured plants showed considerably less disease incidence (30-40%) and severity (10-16%). Injured inoculated plants presented reduced leaf length and leaf area of the crop while the leaf diameter remained unaffected. The lesion number, length and size was substantially enhanced with concomitant infestation of pest and pathogen. Thrips tabaci injury led to more produced symptoms of purple blotch compared to Thrips parvispinus injury. There was substantial decrease in photosynthetic rate and chlorophyll content with stress imposed on plant and the relative stress injury was enhanced. The induction of injury and inoculation of Alternaria porri had an impact on the concentration of total phenolics, total soluble sugars, total proteins, and hydrogen peroxide in onion leaves. Alternaria porri combined with injury caused a more pronounced decrease in total soluble sugars and total protein content but enhanced the total phenolics and hydrogen peroxide content compared to uninjured plants. The dynamic nature of morpho-physiological and biochemical changes owing to stress conditions imposed on onion plants adds an extra layer of complexity in understanding the onion plant physiology and their ability to compensate in response to challenging environment conditions.