Acetic acid bacteria as causal agents of browning and rot of apples and pears

Acetic acid bacteria are associated with apples and pears and have been isolated frequently from rotting fruits. The present work reports a) on the involvement of acetic acid bacteria in the rotting process, b) on the artificial infection of apple disks and entire apples by 159 acetic acid bacteria and c) on the susceptibility of 15 apple and 3 pear varieties.

Nearly all Gluconobacter (101) and Acetobacter (58) strains tested were found to cause a type cf rot and browing in apples and pears not accompanied by a softening of the tissue. The rot inducing capacity is not restricted to acetic acid bacteria or to any of its taxonomic subdivisions. All the apple and pear varieties were susceptible, Golden delicious being the most resistant apple variety. It is suggested that the role of acetic acid bacteria in the post-harvest rotting and browning processes of apples and pears has been underestimated up to now.