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Stomatal openings on boxwood leaves yield entry portals for leaf infection by Calonectria pseudonaviculata

  • Yonghong Guo
  • James Kilcrease
  • John Hammond
  • Margaret PoolerEmail author
Short Communication
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Abstract

The distribution, density, and size of leaf stomata for eight boxwood taxa were investigated using both light and electron microscopy. Stomata, the pores that facilitate gaseous exchange during photosynthesis, were primarily located on the abaxial (lower) epidermis of boxwood leaves with minimal distribution on or along the central vein of the adaxial (upper) surface. Inoculation of boxwood leaves with Calonectria pseudonaviculata at different leaf sites showed that infection occurred only in areas where stomata were present. Scanning and transmission electron microscopic examination of the inoculated leaves also confirmed that the fungal pathogen gains leaf entry through stomatal openings and not by direct penetration of the cuticle. Among the eight boxwood taxa examined, stomatal densities ranged from 116 ± 15 (B. sinica ‘NaNa’) to 326 ± 21 (B. harlandii) stomata per mm2; stomatal size ranged from 500 ± 84 um2 (B. harlandii) to 1052 ± 117 um2 (B. sinica ‘NaNa’); and stomatal area per leaf (density × size) ranged from 88.63 mm2 (‘Justin Brouwers’) to 154.3 mm2 (B. harlandii). No relationship between stomatal density or size and infection rate was observed; relationships between infection rate and stomatal location and stomatal area on the abaxial surface were demonstrated.

Keywords

Boxwood blight Buxus Disease resistance Electron microscopy 

Notes

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.

Statement of human and animal rights

This article does not contain any studies with human or animal subjects performed by any of the authors.

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Copyright information

© This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply 2019

Authors and Affiliations

  1. 1.U.S. Department of Agriculture/Agricultural Research ServiceU.S. National Arboretum, Floral and Nursery Plants Research UnitBeltsvilleUSA
  2. 2.Rutgers UniversityNew BrunswickUSA
  3. 3.Nanotechnology Systems DivHitachi High Technologies America Inc.ClarksburgUSA

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