Abstract
Fusarium wilt in bananas is one of the most devastating diseases that poses a serious threat to the banana industry globally. With no effective control measures available to date, biological control has been explored to restrict the spread and manage the outbreak. We studied the effective biological control potential of different Trichoderma spp. in the management of Fusarium oxysporum f. sp. cubense tropical race 4 (Foc TR4). Expression of the defense related genes and metabolites in banana plants inoculated with Foc TR4 and treated with effective Trichoderma sp interactions were also studied. The in vitro growth inhibition of Foc TR4 by Trichoderma reesei isolate CSR-T-3 was 85.19% indicating a higher antagonistic potential than other Trichoderma isolates used in the study. Further, in in vivo assays, the banana plants treated with the isolate CSR-T-3 T. reesei had a significant reduction in the disease severity index (0.75) and also had increased phenological indices with respect to Foc TR4 treated plants. Enhanced activity of defense enzymes, such as β-1, 3-glucanase, peroxidase, chitinase, polyphenol oxidase, and phenylalanine ammonia lyase with higher phenol contents were found in the Trichoderma isolate CSR-T-3 treated banana plants challenge-inoculated with Foc TR4. Fusarium toxins, such as fusaristatin A, fusarin C, chlamydosporal, and beauveric acid were identified by LC-MS in Foc TR4-infected banana plants while high intensity production of antifungal compounds, such as ß-caryophyllene, catechin-o-gallate, soyasapogenol rhamnosyl glucoronide, peptaibols, fenigycin, iturin C19, anthocyanin, and gallocatechin-o-gallate were detected in T. reesei isolate CSR-T-3 treated plants previously inoculated with Foc TR4. Gene expression analysis indicated the upregulation of TrCBH1/TrCBH2, TrXYL1, TrEGL1, TrTMK1, TrTGA1, and TrVEL1 genes in CSR-T-3 treatment. LC-MS and gene expression analysis could ascertain the upregulation of genes involved in mycoparasitism and the signal transduction pathway leading to secondary metabolite production under CSR-T-3 treatment. The plants in the field study showed a reduced disease severity index (1.14) with high phenological growth and yield indices when treated with T. reesei isolate CSR-T-3 formulation. We report here an effective biocontrol-based management technological transformation from lab to the field for successful control of Fusarium wilt disease caused by Foc TR4 in bananas.
Highlights
Fusarium wilt caused by Fusarium oxysporum f. sp. cubense tropical race 4 (Foc TR4) is considered to be one of the most devastating diseases of bananas limiting banana production worldwide (Ploetz and Pegg, 2000; Dita et al, 2018)
The three Trichoderma isolates used in the study are described as follows; (i) Trichoderma reesei (CSR-T-3, MK050013) isolated from the rhizosphere soil of banana cultivar G-9 grown in salt affected soil, (ii) Trichoderma asperellum (CSR-T-4, MN227242) isolated from the disease suppressive rhizosphere of banana cultivar G-9 grown in the Foc TR4 affected region of Uttar Pradesh, India, and (iii) Trichoderma koningiopsis (CSR-T-2, KJ812401) obtained from the rhizosphere of Saccharam spontaneum in the barren sodic soil of Uttar Pradesh, India
The current gaps in devising management schedules for Fusarium wilt disease include the scarcity of resistant varieties, no effective chemical control measure, the lack of a virulent biological control agent that could work at field level, and their clear mode of action
Summary
Fusarium wilt caused by Fusarium oxysporum f. sp. cubense tropical race 4 (Foc TR4) is considered to be one of the most devastating diseases of bananas limiting banana production worldwide (Ploetz and Pegg, 2000; Dita et al, 2018). The discrimination of Foc TR4 from Foc race 1 proved very efficient with the PCR-based detection employed for secreted in xylem (SIX) genes (Carvalhais et al, 2019) and comparative analysis of various specific primers has ascertained the efficiency of SIX gene-specific primers in the molecular detection of Foc TR4 (Magdama et al, 2019). These advances have paved the way for a reliable dependable confirmatory assay for the early detection/diagnosis of Foc TR4
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