Biochemical compounds are key components in plant-pathogen interaction. Plants become susceptible to various pathogenic microbes due to alteration in these antioxidant compounds. These compounds are help the plants to combat with pathogens. So, study of alterations in biomolecules will be helpful for growers and researchers to develop better preventive measures against brown spot of citrus. For this purpose, experiments were conducted to observe alterations in biochemical compounds infected with brown spot of citrus through artificial inoculation of pathogen. After two years screening of thirty citrus species, six varieties (Susceptible and resistant) were selected. Leaves of resistant (Eruka lemon, Mayer lemon and Citron) and susceptible (Washington navel, Valentia late and Kinnow) cultivars of inoculated and un-inoculated group were collected and analyzed through Nested Structured Design for alterations in biomolecules of citrus leaves. Significant variations (p ≤ 0.05) were present in biochemical enzymes of resistant susceptible types. Susceptible types of plant indicated 2.64,3.31, 1.02, 2.38, 1.74, 4.20 and 0.77, resistant types of plants showed 3.42, 3.72,1.53,2.04,2.51,3.27 and 0.63 μg/g of total phenolic contents, total soluble sugars, SOD, POD, total soluble proteins, Catalases and H₂O₂ respectively. In case of group, Un-inoculated plants of citrus expressed 4.30,4.17, 2.16,1.26,3.30, 2.28, 0.27 while inoculated plants showed 1.76, 2.86, 0.39,3.16,0.94,5.19 and 1.14 μg/g of these compounds. It is concluded from the current findings that alterations in biochemical compounds can serve as effective marker for the documentation of resistant germplasm towards brown spot of citrus.

Keywords:   Pathogen, Catalases, Biomolecules, Significant variations, Resistant germplasm, Valentia late