2.5. Disease incidence
The plants were monitored weekly after treatments were
applied by recording the expression of disease or damage symptoms to assess disease incidence. Plant with chlorotic, necrotic,
curling, mottling, stunting or bunching symptom was considered
as diseases infection. The proportion of infected plants per plot
was calculated and expressed as a percentage of disease incidence
(Galanihe et al., 2004).
2.6. Relative chlorophyll content and chlorophyll fluorescence
Relative chlorophyll content was measured on the upper most
fully expanded leaves of the four individual plants per treatment
at 20, 40, 60, 80 and 100 DAT using chlorophyll meter (SPAD 502,
MINOLTA
TM Camera Ltd., Japan). The measurement of fast chlorophyll fluorescence was taken on the upper surface of the latest
fully expanded leaves from four individual plants per treatments at
09:00–10:00 h, which was used for primary photochemistry detection. Prior to fluorescence measurements, a circular surface of the
upper face was dark-adapted for 30min using dark clips, hence the
induction curve (Fv/Fm ratio) was then estimated by a Plant Effi-
ciency Analyzer (Handy PEA, Hansatech Ltd King’s Lynn, Norfolk,
England) with 600Wm−2
of red (630) light intensity (excitation
intensity). Fv/Fm provides an estimation of the maximum photochemical efficiency or quantum yield of photosystem II (PSII)
(Ouzounidou et al., 2010).
2.7. Leaf photosynthetic rate
An open-path portable photosynthesis system (Li-6400XT, LICOR, Lincoln, Nebraska-USA) was used to determine the net
photosynthetic rate (molm−2
s−1
) per unitleaf area. Three uppermost fully expanded young leaves of the five individual plants per
treatment were randomly chosen and measured at midday (10–11
AM). The data were taken at 20, 40, 60, 80 and 100 DAT.
2.8. Statistical analysis
An analysis of variance was performed using the SAS software
(SAS, 2009). Duncan Multiple Range Test (DMRT) at P ≤ 0.05 was
used to test differences between the treatments.