Differential Adaptation Has Resulted in Aggressiveness Variation of Calonectria pseudonaviculata on Hosts Buxus, Pachysandra, and Sarcococca

Abstract

Calonectria pseudonaviculata (Cps) infects Buxus (boxwood), Pachysandra (pachysandra), and Sarcococca spp. (sweet box); yet, how it adapts to its hosts has been unclear. Here, we performed serial passage experiments with the three hosts and measured Cps changes in three aggressiveness components: infectibility, lesion size, and conidial production. The detached leaves of individual hosts were inoculated with isolates (P0) from the originating host, followed by nine serial inoculations of new leaves of the same host with conidia from the infected leaves of the previous inoculation. All boxwood isolates maintained their capability of infection and lesion expansion through the 10 passages, whereas most non-boxwood isolates lost these abilities during the passages. Isolates from plants of origin (*-P0) and their descendants isolated from passages 5 (*-P5) and 10 (*-P10) were used to evaluate aggressiveness changes on all three hosts with cross-inoculation. While post-passage boxwood isolates gave enlarged lesions on pachysandra, sweet box P5 and pachysandra P10 isolates showed reduced aggressiveness on all hosts. Cps appears to be most adapted to boxwood and less adapted to sweet box and pachysandra. These results suggest speciation of Cps, with its coevolutionary pace with the hosts the fastest with boxwood, intermediate with sweet box, and the slowest with pachysandra.

First report of Calonectria henricotiae causing box blight in Spain

“…The mould was suspended in 15 µL sterile distilled water then transferred onto a glass slide for microscopy. Following observations of rod‐shaped conidia, typical of Calonectria spp., 1‐µL drops of the suspensions were pipetted from slides onto acidified potato dextrose agar (PDA) for isolation (Kong et al., 2023). Clean colonies were only obtained from the Madrid and Sainte‐Foy‐la‐Grande samples (Figure 3) and were subcultured on regular PDA.…”

Plant and Trees Pathogens: Isolation, Characterization and Control Strategies (1.0)

“…However, the mechanism of this pathogen's adaptation to different host plants has been undefined until recently. Kong et al [9] conducted a series of experiments to understand the adaptation process of Cps to its hosts, by measuring three components of aggressiveness: infectibility, lesion size, and conidial production.…”

“…The results indicated that all boxwood isolates maintained their capability of infection and lesion expansion through the ten passages, whereas most non-boxwood isolates lost these abilities during the passages. Isolates from plants of origin (-P0), and their descendants isolated from passages 5 (-P5) and 10 (*-P10), were used to evaluate changes in aggressiveness toward all three hosts with cross-inoculation [9].…”

“…Boxwood is a valuable landscape shrub, and the discovery of Cps as most adapted to boxwood underscores the importance of effective disease management practices for this plant species. Contrastingly, pachysandra and sweet box may be less susceptible to the disease and may require fewer management interventions [9].…”