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Comparison of five potato-based protocols for conidial production by Calonectria pseudonaviculata

Shu Yang: Hampton Roads Agricultural Research and Extension Center, Virginia Tech

<div>Boxwood blight caused by <em>Calonectria pseudonaviculata</em> (<em>Cps</em>) is an emerging disease of great concern to the ornamental horticulture industries, landscapers, public garden managers, and homeowners in the U.S. and many other countries. The primary objective of this study was to compare five protocols developed in different labs for conidial production, a critical step for successful investigations into <em>Cps</em> biology, disease epidemiology and management. These protocols all utilize potato-based media but they differ in medium type, composition and strength, as well as cultural processes and conditions. The comparative analysis focused on conidial yield and aggressiveness in boxwood infection using two <em>Cps</em> isolates 11D05 and 12A02 recovered from boxwood and sweet box, respectively. The associated time requirement and material cost were also considered. Overall, both isolates were most prolific using the potato dextrose broth (PDB) protocol with 11D05 producing 3.39 ± 1.57 × 10<sup>7</sup> conidia Petri dish<sup>-1</sup> and 12A02 having 2.84 ± 1.33 × 10<sup>7</sup> conidia dish<sup>-1</sup>. The resultant conidia were equally, if not more, aggressive in infecting <em>Buxus sempervirens</em> cv. Suffruticosa than those produced with other protocols. The PDB protocol also was more time-efficient and cost-effective than the other protocols evaluated in this study. These results will add quality and productivity to ongoing boxwood blight research, consequently better using the limited resources. Strengths of the four other protocols were also noted and discussed which would be good leads to further improving the PDB protocol.</div>