Abstract
Bacterial spot, caused by a group of Xanthomonads (Xanthomonas spp.), is a devastating disease. It can adversely affect the Capsicum annum productivity. Scientists are working on the role of antioxidants to meet this challenge. However, research is lacking on the role of antioxidant enzymes and their isoforms in the non-compatible pathogen and host plant interaction and resistance mechanisms in capsicum varieties. The present study was conducted to ascertain the defensive role of antioxidant enzymes and their isoforms in chilli varieties Hybrid, Desi, Serrano, Padron, and Shehzadi against bacterial spot disease-induced Xanthomonas sp. The seedlings were inoculated with bacterial pathogen @ 107 CFU/mL, and samples were harvested after regular intervals of 24 h for 4 days followed by inoculation. Total plant proteins were extracted in phosphate buffer and quantified through Bradford assay. The crude protein extracts were analyzed through quantitative enzymatic assays in order to document activity levels of various antioxidant enzymes, including peroxidase (POD), Catalase (CAT), Ascorbate peroxidase (APX), and Superoxide dismutase (SOD). Moreover, the profiles appearance of these enzymes and their isoforms were determined using native polyacrylamide gel electrophoresis (PAGE) analysis. These enzymes exhibited maximum activity in Hybrid (HiR) cultivar followed by Desi (R), Serrano (S), Padron, and Shehzadi (HS). Both the number of isoforms and expression levels were higher in highly resistant cultivars compared to susceptible and highly susceptible cultivars. The induction of POD, CAT, and SOD occurs at the early stages of growth in resistant Capsicum cultivars. At the same time, APX seems to make the second line of antioxidant defense mechanisms. We found that modulating antioxidant enzymes and isoforms activity at the seedling stage was an important mechanism for mitigating plant growth inhibition in the resistant ones.
Highlights
Bacterial spot, caused by a group of Xanthomonads (Xanthomonas spp.), is a devastating disease
Kuznaik and Sklodowska[29] analyzed peroxisomal antioxidant enzymes viz. Superoxide dismutase (SOD), CAT, Glutathione peroxidase (GPX), and ascorbate–glutathione (AA-GSH) cycle activities in tomato infected with B. cinerea
It was early noticed increases in SOD, CAT and GPX indicating that initial infection induced their activities and the activation of antioxidant plant defense, which was followed by a progressive inhibition concomitant with disease symptoms development
Summary
Bacterial spot, caused by a group of Xanthomonads (Xanthomonas spp.), is a devastating disease. The present study was conducted to ascertain the defensive role of antioxidant enzymes and their isoforms in chilli varieties Hybrid, Desi, Serrano, Padron, and Shehzadi against bacterial spot disease-induced Xanthomonas sp. Kuznaik and Sklodowska[29] analyzed peroxisomal antioxidant enzymes viz. SOD, CAT, Glutathione peroxidase (GPX), and ascorbate–glutathione (AA-GSH) cycle activities in tomato infected with B. cinerea It was early noticed increases in SOD, CAT and GPX indicating that initial infection induced their activities and the activation of antioxidant plant defense, which was followed by a progressive inhibition concomitant with disease symptoms development. In the current study, we investigated the role of different antioxidant enzymes (SOD, POD, CAT, and APX) in the defense mechanism of capsicum cultivars, enabling them to mitigate the infection damage on them. It is hypothesized that antioxidant enzymes (SOD, POD, CAT, and APX) could be evolved as a defense of capsicum mechanism against the bacterial spot pathogen during their coevolution process in the past time
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