Latent infection of loquat leaves and flowers by Pestalotiopsis spp., cause of loquat fruit rot

Abstract

Species of Pestalotiopsis are known to cause loquat fruit rot, but despite numerous studies of its life cycle, the source of inoculum remains unknown. Because this genus includes endophytes, we hypothesized that Pestalotiopsis fungi inhabit healthy leaves and flowers. We thus investigated the pathogenicity of isolates from healthy leaves and flowers against loquat and identified the isolates. Of the 10 from leaves, all were nonpathogenic on leaves and unwounded ripe fruits but pathogenic on wounded ripe fruits. In contrast, all 40 strains from flowers were nonpathogenic on unwounded fruits and leaves. However, on wounds, they formed four groups: (1) only pathogenic on fruits (19 strains), (2) pathogenic on both fruits and leaves (14 strains), (3) only pathogenic on leaves (2 strains), and (4) nonpathogenic on fruits and leaves (5 strains). A phylogenetic analysis based on ITS, tub2, and tef1 from our strains and isolates previously isolated from loquats indicated that some of the strains were in the same lineage, irrespective of their origin (leaves, flowers, or rotting fruit). Furthermore, the pathogenicity on leaves and fruits varied among strains, even within the same clade. Thus, Pestalotiopsis fungi that can cause fruit rot were present in healthy leaves.