Saprophytic suppression of <i>Botrytis cinerea</i> sporulation on kiwifruit leaf tissue

Abstract

To determine the ability of Erwinia herbicola Eh252, to inhibit bacterial soft rot caused by Erwinia species, we compared the amount of rot on carrot slices treated or not treated with Eh252 after incubation in compost infected with Erwinia carotovora pv. carotovora. Compost was used to mimic the conditions under which bacterial soft rot develops and was preparedby mixing rotten carrot slices inoculated with Fcc 11523. When carrot slices were dipped in highly concentrated bacterial suspensions ofEh252, no rot was observed until five weeks incubation at 28°C, while under the same conditions, 83% of slices dipped in 10mM MgSO 4 , which was used as a control, were infected. After nine weeks of incubation 50% of the carrot slices treated with Eh252 still showed no sign of infection. Lower concentrations of Eh252 conferred lower levels of protection. Eh252 produces an antibiotic-like molecule which in vitro inhibits all Erwinia species causing soft rot, and inhibits Eccll523 on potato and carrot slices in laboratory assays. When carrot slices were dipped in a bacterial suspension of a non-antibiotic producing mutant of Eh252, protection was generally not as good as that conferred by Eh252. These results indicate that Eh252 can control soft rot on carrot slices in compost, and that one of the mechanisms involved is antibiotic production.