RT Journal Article
SR Electronic
T1 Photosynthetic Performance of Pinot gris (<em>Vitis vinifera</em> L.) Grapevine Leaves in Response to Potato Leafhopper (<em>Empoasca fabae</em> Harris) Infestation
JF American Journal of Enology and Viticulture
JO Am. J. Enol. Vitic.
FD American Society for Enology and Viticulture
SP ajev.2012.11111
DO 10.5344/ajev.2012.11111
A1 Marcel S. Lenz
A1 Rufus Isaacs
A1 James A. Flore
A1 G. Stanley Howell
YR 2012
UL http://www.ajevonline.org/content/early/2012/05/15/ajev.2012.11111.abstract
AB Potato leafhopper (Empoasca fabae Harris) is a polyphagous insect pest that feeds on Vitis vinifera L. grapevines in North America. In sensitive grape cultivars such as Pinot gris, feeding symptoms include leaf yellowing, leaf cupping and stunted vine growth. Two greenhouse experiments were conducted to determine how photosynthesis and other physiological processes are affected by E. fabae infestation. In Experiment I, Pinot gris leaves at four different positions along shoots were infested with either 0, 1, 2, 4 or 8 E. fabae nymphs for 43 hours to determine how the relationship between infestation level and leaf position affects leaf photosynthesis, and to determine whether or not damage thresholds exist for the photosynthetic response. Empoasca fabae infestation was inversely proportional to carbon assimilation (A), transpiration (E) and stomatal conductance (Gs) and directly proportional to internal CO2 concentration (Ci). There was a positive correlation between A and Gs, while A and Ci were negatively correlated indicating that reductions in A were due to both stomatal and non-stomatal limitations. Damage thresholds, defined as the number of insects necessary to cause damage to the plant, were calculated for A, E, Gs and Ci at most leaf positions. In Experiment II, response curves were generated for infested and uninfested regions of the same leaves to determine how light and CO2 utilization were affected by E. fabae infestation. Declining A in response to E. fabae infestation was due to a decreased capacity of leaf tissues to utilize light and CO2. Reductions in A were correlated with decreases in Gs and increases in Ci and thus we again conclude stomatal and non-stomatal limitations are relevant, with evidence of photosynthetic compensation in the post-infestation period. These results indicate that E. fabae infestation causes injury through rapid effects on the capacity of leaves to produce photosynthate through effects on internal tissues and on stomata. These effects might be transient at low infestation levels but leaf tissue can be compromised at higher infestation levels, leading to irreversible damage.