Involvement of Hydrogen Peroxide in recovery of banana plant from Xanthomonas Wilt disease

Abstract

Plants cannot avoid interaction with microbes, a fraction of which are pathogens. When a plant interacts with pathogenic microbes, the plant immune system is activated which triggers various defence responses. The responses include production of, or expression of, molecules, genes and enzymes with different roles. A group of molecules referred to as reactive oxygen species (ROS) dominate the early defence reactions in plants after pathogenic attack. Hydro-gen peroxide (H2O2) is a key ROS which plays frontline defence roles. The objective of this study was to assess accumulation of H2O2 and determine its localization in tissues of the East African Highland Banana (EAHB) cultivars. Plantlets of Kayinja and Mbwazirume varieties inoculated with Xanthomonas campestris pv Musacearum (Xcm) were used in this study. Plantlets of each of Mbazirume and Kayinja cultivars were inoculated with Xcm while control plantlets of each of the cultivars were left uninoculated. Sample tissues from leaves, pseu-dostems and corms were collected at different time intervals post Xcm inoculation for analy-sis. Ninety samples of plant tissues which were collected from leaves, pseudo-stems and corms of Xcm inoculated and control plantlets of Kayinja and Mbwazirume cultivars were analysed in the laboratory using two methods; (a) by staining with diaminobenzidine (DAB) followed by microscopy (b) by colorimetry and spectrophotometric method for quantitative analysis to determine histolocalisation of H2O2. Induced accumulation of H2O2 was detected in all Xcm inoculated plantlets. The highest accumulation was detected in corms of each of the plantlets at one hour post inoculation (hpi) and a second increase was observed after 6-hpi and peaked at 12-hpi. Although Xcm induces production of hydrogen peroxide in Xcm inocu-lated tissues, its accumulation is significantly influenced by length of time post inoculation. However, hydrogen peroxide accumulation was not dependent on the cultivar. Thus, early accumulation of H2O2 in tissues informs a decision of early intervention in management of Xcm infected plants by Single Diseased Stem Removal (SDSR) irrespective of the cultivar.