conference schedule and program with abstracts - Horticulture ...

P-99
Berry cracking caused powdery mildew (Uncinula necator) infection in ‘Fujiminori’
grapevines (Vitis sp.)
H.-S. Shin*, S.-I. Oh, I.-C. Son, Y.-J. Oh, J.-Y. Park, D. Kim
Dept. of Horticultural Science, Chungbuk National University, Cheongju, Korea
*Corresponding author: joker1016@nate.com
Powdery mildew (Uncinula necator) is one of the common grape diseases in protected rainshelter
cultivation in Korea. Wounds from disease infection may provide the starting point of
cracking in susceptible tetraploid grapevines. To find out the effect of U. necator infection on
berry cracking, morphological and histological observation was conducted using the cracking
susceptible ‘Fujiminori’ grape cultivar. The intact berry rate was lower after the inoculation
(85.8%) than in the control vines (89.3%). Cluster weight and numbers of berries per cluster in
inoculated vines was significantly lower, with 722.6 g and 38.6 compared with 842.2 g and 40.2
in controls. Inoculation with powdery mildew reduced the firmness of pericarp to 1.11 kg/Ø5mm
from the 1.31 kg/Ø5mm of controls. The berry cracking rate under critical turgor pressure was
also decreased from 18.0% to 29.0% after inoculation of U. necator. The degree of cell wall
degradation was measured by cell wall content from 10 g pericarp. The cell wall content of
inoculated ‘Fujiminori’ was reduced 31.3% with collection of 311.7 mg compared with untreated
vines of 453.7 mg. Polygalacturonase, one of the major enzymes inducing cell wall degradation,
activity was increased from 0.143 to 0.204 units/mL in U. necator infected berries. In the results
from powdery mildew inoculation, the invasion of hypha in early berry growth stages before
veraison promotes cell breakdown between the sub-epidermal and the epidermal layer by
secreted cell wall degradation enzymes even no visible disease symptom in the berry.
180