Neoscytalidium dimidiatum (Penz.) Crous & Slippers, a major pathogen affecting dragon fruit production globally, has also been documented causing diseases on economic or landscape crops in many countries. Despite the wide geographical distribution and host range of the pathogen, knowledge of the genetic and biological characteristics of N. dimidiatum from different spatiotemporal and host populations is limited. This study compared the phylogenetic and phenotypic diversity of the N. dimidiatum populations collected from dragon fruit between 2010 and 2021 in Taiwan with the isolates obtained from other hosts and countries. A multilocus sequence analysis revealed that the N. dimidiatum from Taiwan clustered based on their hosts, dragon fruit and cattleya, regardless of the spatiotemporal origins, whereas the isolates from other countries exhibited a slightly higher phylogenetic diversity. Limited phylogenetic diversity suggested that asexual reproduction may be the primary approach for N. dimidiatum to maintain the population in Taiwan. Nevertheless, variations in colony color, mycelial growth, and spore germination at different temperatures were evident within and among populations at different spatiotemporal scales. For instance, the population collected from dragon fruit in northwestern and eastern Taiwan had a significantly better mycelial growth rate at 40 ℃, compared to the populations collected from southwestern Taiwan. All tested isolates from different hosts were found to cause lesions on dragon fruit cladodes, however, generally larger lesions and significantly shorter latent periods were observed in the isolates collected from dragon fruit. The results suggested that phenotypic plasticity in clonal N. dimidiatum populations, along with a better fit in the original host, and the potential of infecting hosts that were under heat or other abiotic stresses may contribute to the global emergence of the pathogen.
Keywords: fitness traits; host range; pathogenicity; pitahaya; population genetics.