48 research outputs found
Comparative physiological and histological investigations on resistant and susceptible pomegranate genotypes infected with Xanthomonas axonopodis pv. punicae
269-279Xanthomonas axonopodis pv. punicae (Xap) is a bacterial pathogen wreaking havoc in pomegranate cultivation. It causes
bacterial blight disease dwindling yield and making fruit unfit for consumption. Physiological and histological investigations
during host-pathogen interaction are prerequisite to assess the onset of defense mechanism in plants. Therefore, we tried to
compare the pomegranate resistant (IC 318734) and highly susceptible (Ruby) genotypes challenged with Xap. The bacterial
suspension containing Xap cells of 0.3 OD600 (~106 to 107CFU mLâ1) was used for challenge inoculation. Uniformly grown
resistant and highly susceptible plants were selected, the surface of leaves was pricked and spray-inoculated with bacterial
suspension using native strain IIHR1 (NCBI Gen Bank ID: KT 222897). Simultaneously, the control plants were also
sprayed with only distilled water and observed. A total of three replications with five plants per replication were maintained
and evaluated under completely randomized design. Physiological investigations were recorded using Portable
photosynthesis system (LCpro+, ADC BioScientific limited, UK) for one cycle of disease progression viz., 0, 1, 5, 10, 15
and 20 days after bacterial spray inoculation (DAI). Significant changes in gas exchange parameters were witnessed on
pathogen inoculation. Higher reduction in mean percent change of photosynthetic and transpiration rate, instantaneous water
use efficiency, internal CO2 content, stomatal conductance and relative water content were noticed in highly susceptible
genotype than resistant one. On contrary, an increased percent mean change of intrinsic water use efficiency, carboxylation
capacity and lignin was documented in resistant genotype. Relative injury caused due to bacterial infection was found high
in highly susceptible genotype than resistant one. Histological investigations in highly susceptible and resistant genotype
were studied on 20th day of Xap inoculation using Scanning Electron Microscopy. Highly susceptible genotype exhibited
maximum deformed cells, tissues and other visible abnormalities upon Xap inoculation. Thus, this study forms a basis for
effective disease management and breeding programmes in pomegranate