World’s first report of Erysiphe hyperici causing powdery mildew on fenugreek
INTRODUCTION
Powdery mildew disease was observed on
fenugreek (Trigonella foenum-groecum L.) in the farm
of Navsari Agricultural University, Navsari, Gujarat
during the year 2015. Subsequently, disease has been
observed covering wide area in the winter of year 2016
and 2017. Infection starts on the leaves as a small round
to irregular powdery mycelia which gradually increases
in the size and merge covering the entire leave (Fig. 1).
All the above ground parts of the plant including petiole,
stem and pod were covered with the white colored
powdery mass of the mycelium and conidia within 15-20
days (Fig. 2). Early infected plant remained dwarf bearing
very few pods either empty of bearing few small size
shriveled grains of no significance. Infection occurs on
both the surface of the leaf, however, higher colonization
was seen on adaxial surface. Pathogenicity test was
proved by gently pressing the adaxial surface of an
infected leaf with abundant sporulation onto the adaxial
surface of a healthy leaf of 45 days old fenugreek (cv.
LOCAL) plants grown at 25oC. Inoculated and control
plants were covered with 50 micron clear polyethylene
bags for 48 h after inoculation. Symptoms observed after
a week was consistent with the originally infected field
plants, while no symptoms were observed on the control
plants. Microscopic observation revealed that the
pathogen growing on the inoculated plants was consistent
with the morphology of the original fungus.
The conidiophores were 13.80-18.37 µm long,
whereas the width from the widest part of conidiophores
was 4.96-7.04 µm. Hyaline conidia developed in acropetal
succession were ellipsoid in shape with 29.25-39.92 µm
length and 11.74-19.37 µm width. Fibrosin bodies in
conidia were not found. Conidial cell wall showed
evidence of faint reticulation (Fig. 3). Similar conidial
morphology of the conidiophores with conidia was
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