Abstract:
An investigation was carried out to evaluate imported hybrid rice varieties against major
diseases under natural epiphytic conditions of Bangladesh during the boro season of
2008-09 at Sher-e-Bangia Agricultural University research farm. Fifteen hybrids (13
imported, 2 local) viz. Hira-I, Hira-2, ACI-l, Surma-I, Tal-l, Modhumoti-2, Krishan-2,
Sonar Bangla-6, Richer-I 0 I, Moyna, Tia, Tinpata, Aloron , BRRI hybrid dhan-I, BRRI
hybrid dhan-2 and 2 HYV check varieties viz. BRRI dhan ..28 and BRRI dhan-29 were
evaluated regarding disease incidence and severity at 3 stages and the effect of diseases
on yield and yield contributing characters. Six field diseases viz. brown leaf spot
(Bipolaris oryzae), leaf blast (Pyricularia grisea), sheath blight (Rhizoctonia solani),
BLB (Xanthomonas campestris pv. oryzae), narrow brown spot (Cercospora oryzae), and
altemaria leaf spot (Alternaria tenuissima) were recorded and identified. The incidence
and severity of diseases varied significantly from one another. The disease incidence and
severity of brown spot at maturity stage were recorded from 15.51% to 25.85% and 0.64
to 4.15 (0-9 scale), respectively where Him-2 and ACI-I varieties showed good
performance against the disease. In case of leaf blast, the disease incidence and severity
ranged from 8.82% to 21.28% and 1.01 to 6.21 (0-9 scale), respectively at maturity stage
where Him-2 showed the lowest incidence (8.82%) and severity (1.01). Richer-lot
showed the highest incidence (21.28%) and severity (6.21). Disease incidence and
severity of sheath blight varied from 9.27% to 25.82% and 1.52 to 8.74 (0-9 scale),
respectively at maturity stage where Hira-I, Hira-2 and ACI-l showed better result
against the disease. In case of BLB, the disease incidence and severity ranged from
13.28% to 28.92% and 1.21 to 8.72 (0-9 scale), respectively at maturity stage where TajI,
Krishan-2, Aloron and Moyna were severely affected by this disease. In case of narrow
brown leaf spot, the disease incidence and severity ranged from 6.27% to 12.23% and
1.10 to 5.84 (0-9 scale), respectively at maturity stage where, the highest incidence
(12.23%) and severity (5.84) was recorded on Modhumoti-2 and the lowest incidence
(6.27%) and severity (1.10) was observed on ACI-1. Disease incidence and severity of
altemaria leaf spot also varied from 13.27% to 32.12% and 1.42 to 3.00 (0-9 scale),
respectively at maturity stage. The highest growth and yield contributing characters
recorded on ACI-l, Hira-I and Him-2 considering plant height, panicle length, effective
panicle and filled grain. Grain yield ranged from 4.50 tJha to 10.77 tIha. In case of
hybrids, the highest grain yield (10.77 tIha) was recorded on Hira-I, Hira-2 and ACI-l
also gave. the better yield 9.72 tlha and 9.70 tlha respectively. The lowest grain yield
(7.90 tlha) was found in Krishan-2 which was statistically identical with Richer-10l (7.92
t/ha). It was observed that disease incidence and severity was gradually increased from
flowering stage to maturity stage, with the age of the plant. Minimum incidence and
severity gave the maximum yield.
Description:
A Thesis
Submitted to the Faculty of Agriculture,
Sher-e-Bangla Agricultural University, Dhaka
in Partial fulfillment of the requirements
for the degree of
MASTER OF SCIENCE (MS)
IN
PLANT PATHOLOGY