Effectiveness of four plant extracts and chitosan against xanthomonas campestris pv. campestris the causal agent of black rot disease on cabbage

Abstract

The aims of this study were to detect of X. campestris pv. campestris from five cabbage cultivars, to test the effectiveness of plant extracts and chitosan in inhibiting the growth of X. campestris pv. campestris, to test the effectiveness of seed treatment using plant extracts and chitosan to control X. campestris pv. campestris in infected cabbage seeds, and to evaluate the effect of seed treatment to seed viability. The results of this research showed that betel extract, clove extract, and chitosan had ability to inhibit X. campestris pv. campestris growth, while binahong and turmeric extracts did not show inhibitory effect. Cabbage seed cultivar Green Hero was positively infected by X. campestris pv. campestris. X. campestris pv. campestris developed yellowish green colonies on SX medium. DNA fragment of 535 bp was successfully amplified using PCR with spesific primer for hrpF gene of X. campestris pv. campestris, i.e. XCF and XCR. The treatment with 2% betel extract, 3% clove extract, and 0.5% chitosan totally inhibited bacterial growth in NB medium and suppressed over 99% inoculum density after 50 minutes soaking seed. Betel and clove extracts suppressed the infection rate on seed by 84% and 97.33%, respectively. Chitosan did not reduce the level of infection due to the high initial infection of seeds. The treatments did not decrease seed viability as indicated by seed germination rates (95%). It was evidenced that betel extract, clove extract, and chitosan have the potential to be developed as quarantine treatment techniques to suppress infection of X. campestris pv. campestris in cabbage seeds.