Biochemical base of resistance in citrus against canker disease

Biochemical compounds are important factors in plant-disease interactions. Plants become prone to pathogen infection due to alterations in these compounds which help the plants in restricting the pathogens. Knowledge of these alterations is helpful for researchers to develop some concrete solutions for the management of canker disease. For this purpose, experiments were conducted with three replications to find out the alterations in biochemical compounds of citrus leaves infected with canker disease by artificial inoculation through syringe method. So, six varieties (three susceptible and three resistant) were selected after two years screening of thirty species of citrus under natural field conditions. Leaves of susceptible (Grapefruit, Succari, Kinnow) and resistant (Kumquat, Jaffa, China lemon) varieties of inoculated and un-inoculated groups were collected and analyzed for variation in biochemical compounds by using Nested Structured Design. Variations (p ≤ 0.05) were observed in the biochemical compounds among the treatment types. Resistant type of plants expressed 3.35, 2.90, 1.01, 2.10, 2.50, 3.18, and 0.66 µg/g, susceptible type expressed 2.29, 2.49, 1.36, 2.41, 1.73, 4.13 and 0.86 µg/g of total phenolic contents, total soluble sugars, super oxidase dismutase, peroxidase, total soluble proteins, catalase and hydrogen peroxide respectively, while in case of groups, inoculated pants expressed 1.59,2.52, 1.98, 3.20, 0.93, 5.11 and 1.21 µg/g and un-inoculated group exhibited 4.05, 2.87, 0.39, 1.30,3.29, 2.19 and 0.30 µg/g. These variations can be used as biochemical markers to identify source of resistance in citrus species against canker disease.