Quercus chrysolepis foliage supports sporulation of Phytophthora ramorum.

Author , ,
Date 2012
Publication 6th IUFRO Meeting Working Party 7-02-09, Phytophthora in Forests and Natural Ecosystems Meeting. September 9 – 14, 2012. Córdoba-Spain.
Key Words
AbstractFoliar infections are often considered the primary source of Phytophthora ramorum inoculum in California forests. Tanoak (Notholithocarpus densiflorus) is susceptible to fatal trunk infections, but is capable of supporting sporulation on its foliage and twigs. However, infection and sporulation on foliage of California oaks (e.g., coast live oak, Quercus agrifolia) appears to be negligible; trunk infections on these oaks depend on proximity to other hosts supporting pathogen sporulation. In contrast to other California oaks, canyon live oak (Quercus chrysolepis) has been found to suffer from both trunk cankers [1] and leaf and twig blight [2]. To determine the sporulation potential of Q. chrysolepis foliage and twigs, we immersed leaves, twigs, and petiols on detached branches in a zoospore suspension and incubated them in moist chambers for 14 days. For comparison, N. densiflorus and Q. agrifolia were also included. Most inoculated plants developed blight symptoms. Symptomatic foliage was sampled by removing 5 mm dia. discs from the tissue. Stems were sampled by excising 3 cm from infected areas. Samples were placed in 1.5 ml of water in micro-centrifuge tubes and vortexed for 30 s to dislodge sporangia. The plant tissue was removed, and the suspension stained with 5% cotton blue in lactophenol. Sporangia in the suspensions were counted at 50 X magnification. Sporangia production predominated along leaf veins. Q. chrysolepis leaves supported sporangia production, with numbers lower and significantly different than N. densiflorus; both species produced significantly higher numbers of sporangia than Q. agrifolia. Sporulation from stems had a similar pattern but there were no statistically difference between species. [1] Aram, K.; Swiecki, T.; Bernhardt, E.; and Rizzo, D.M. Canyon live oak (Quercus chrysolepis) is susceptible to bole infection by Phytophthora ramorum. Phytopathology, 101:S8. [2] Murphy, S.K. and Rizzo D.M. 2003. First report of Phytophthora ramorum on canyon live oak in California. Plant Disease, 87: 315.
Full Citation Aram, K.; Moral, J.; and Rizzo, D.M. Quercus chrysolepis foliage supports sporulation of Phytophthora ramorum. Poster. 6th IUFRO Meeting Working Party 7-02-09, Phytophthora in Forests and Natural Ecosystems Meeting. September 9 – 14, 2012. Córdoba-Spain.