Abstract
The effectiveness of Bion (inducer of resistance) either alone or in combination with
Amistar and Tilt was evaluated against leaf spot of wheat (Bipolaris sorokiniana).
Collected eighty six monoconidial isolates of B. sorokiniana were identified as 65
physiologic races and 12 pathotypes. Seed treatment with Bion @ 50 mg/L increased
germination by 31.16 over control in blotter, where Bion @ 25 mg/L increased 98.42%
vigor index over control. Seed treatment with Bion increased seed germination and vigour
index of wheat cv. Kanchan in pot trials. Seed treatment with Bion @ 50 mg/L reduced
leaf spot severity from 41 to 31, 71 to 32 and 61 to 31 when plants were inoculated by the
pathotype-1, pathotype-2 and pathotype-3, respectively. Seed treatment with Bion reduced
leaf spot severity from 71 to 41 and 92 to 91 in heading and flowering stages, respectively
during 2000-2001 cropping season and in 2001-2002 the disease severity turned down
from 95 to 92 at hard dough stage. Number of spikes/m², number of healthy spikes/m²,
number of grains/ear, healthy grains/ear, weight of grains/ear and healthy grains/ear have
been found to be increased due to application of Bion. Bion @ 25 mg/L resulted higher
grain yield (4.59 t/ha) which was 49.51% increased over control in 2001-2002. Bion as
soil drenching showed good effect in reducing % LAD up to 57.25% when plants were
inoculated with B. sorokiniana at flowering stage. Soil drenching with Bion @ 50 mg/L
and @ 25 mg/L resulted 26.29% and 67.52% reduction of conidia production/leaf segment
over control (excised leaf method). Soil drenching with Bion resulted marked reduction of
leaf spot severity at heading, flowering and hard dough stages when plants were
inoculated with B. sorokiniana in pot trials. Soil drenching with Bion @ 25 mg/L reduced
43.74% diseased spikes/m² over control in 2000-2001 and 25 mg/L increased 21.98% and
26.81% grain yield over control in 2000-2001 and 2001-2002, respectively. Foliar spray at
30 days after sowing (DAS), Bion @ 50 mg/L and 25 mg/L resulted 26.15% and 40.61%
reduction of % LAD over control on excised leaf when leaves were inoculated with B.
sorokiniana at flag leaf stage. Bion as foliar spray at 30 and 45 DAS showed reduction of
leaf spot severity when plants were inoculated at flag leaf, flowering and hard dough
stages in pot trials. Number of grains/ear, number of healthy grains/ear, weight of
grains/ear, weight of healthy grains/ear, 1000-grain weight and grain yield/pot were
increased by spraying Bion at 45 DAS. Spraying Bion in combination with Tilt and
Amistar significantly increased grain yield/pot. Foliar spray of Bion in the field at 30 and
45 DAS showed marked reduction of leaf spot severity at flowering and hard dough stage.
Foliar spraying at 30 DAS with Bion @ 50 mg/L in 2001-2002 resulted 17.0% higher
grains/ear over control and Bion @ 25mg/L significantly increased grain yield in 2000-
2001 by 15.67% over control. Foliar spray at 45 DAS Bion @ 25mg/L resulted 17.03%
higher grains/ear over control. Bion @ 50mg/L and 25mg/L significantly increased
number of healthy grains/ear by 15.32% and 20.35%, respectively and 1000-grain weight
by 7.75% and 1.32%, respectively over control in 2000-2001 and 2001-2002 respectively.
Bion @ 50 mg/L and 25 mg/L resulted 3.98 and 3.94 t/ha grain yield, respectively in
2000-2001 by 5.29% and 4.23% increase over control. Foliar spray of Bion @ 50 mg/L
and 25 mg/L also increased grain yield by 6.54% and 7.74% over control, respectively in 2001-2002.