Potting medium after being autoclaved for 45 min at 121 C on
two consecutive days was filled into pots (9 cm diameter) as
described earlier (Hariprasad et al., 2009). Seeds bacterized with
RCB were sown and allowed to grow with day/night light cycle
of 16/8 h and temperature of 28/20 C, at 65% relative humidity
under greenhouse conditions. Fourteen days after sowing (DAS),
the seedlings were thinned to allow one seedling/pot and 25 DAS
they were spray inoculated with PCB till runoff. Individual seed
and foliar spray treatments, and also a combination of seed and
foliar spray treatments were followed. Control seedlings raised
from seeds treated with distilled water were also sprayed with distilled
water. Thirty-five day-old seedlings were uprooted and for
each treatment mean shoot length (MSL), mean root length
(MRL), average fresh weight (FW) and dry weight (DW) were calculated.
A particular bacterial treatment had a set of 18 pots having
six seed treated pots, six foliar treated pots and six combined seed
and foliar treated pots, apart from six control seedling pots. The
experiment was repeated thrice and the arrangement of such pots
was randomized in the subsequent replications.
In the separate experiment conducted to analyze the increase in
leaf surface area caused by phylloplane bacteria, plants of equal
age bearing topmost leaf pairs with almost equal surface area were
selected. After measuring initial leaf surface area, phylloplane colonizing
bacteria (1 108 cfu/mL) were spray inoculated till runoff.
Seedlings were further incubated for 10 days under greenhouse
conditions and at the end of incubation period, the percentage
increase in leaf area was calculated using the formula:
% increase in leaf area ¼ ½ðFLA ILAÞ=FLA 100
where, ILA and FLA are initial and final leaf areas respectively.
Seedlings sprayed with distilled water served as control. For
each treatment, 20 leaf pairs were maintained and the whole
experiment was repeated thrice.