Abstract:
Experiments were conducted for identification and characterization to study pathogenic
variation among Magnaporthe oryzae isolates. Eight blast resistant advanced lines of rice
developed by BRRI were tested phenotypically and at molecular level for the presence of
Pi9 gene and their yield and yield attributes were studied. The experiments were carried
out at Bangladesh Rice Research Institute (BRRI). The three isolates of Gazipur, Rangpur
and Khulna were morphologically confirmed on the basis of three celled (2 septate) and
pyriform hyaline conidia. Cultural characteristics on PDA, PSA and OMA media and
mycelial growth as well as sporulation of the isolates were considered for determination of
morphological variation. Cultural characteristics of three isolates showed different color
(olivaceous, brownish or greyish to black), margin (filamentous, entire or undulate),
surface texture (velvety or wrinkled) and colony form (regular or irregular) but same in
case of elevation (flat) in different media. Sporulation of Khulna isolate was higher
compared to others. Molecular detection of M. oryzae was confirmed using four specific
primers namely; Bt1a/Bt1b, CAL-228/CAL-737, ACT-512/ACT-783, ITS1/ITS4 by
amplifying fungal targeted region; beta tubulin (515 bp), calmodulin (510 bp), actin (260
bp), Internal Transcribed Spacer (520 bp), respectively in expected position. Eight Pi9
gene introgressed blast resistant lines were evaluated along with donor parent (IRBL9-W)
as resistant check and recurrent parent (BRRI dhan28) as susceptible check variety.
Phenotypic reaction for blast resistance indicated that six lines (PL-6, PL-17, PL-21, PL22,
PL-26,
PL-35)
showed
resistant
reaction
(score
0-2)
and
only
one
line
(PL-34)
showed
susceptible
reaction (score 4). BRRI dhan28 gave average score 3.75 (highest score 5)
which was susceptible and IRBL9-W gave average score 0.5 (highest score 1) which was
resistant to blast. These resistant lines were amplified with two linked markers RM8225
(172 bp) and NMSMPi9-1(168 bp) and all the phenotypically resistant lines gave the band
at similar position with the linked markers. PL-21 gave maximum yield (4.47 t/ha) among
the tested lines which was similar to BRRI dhan28 (4.94 t/ha). Therefore, it could be
concluded that except PL-34, all the developed lines have Pi9 gene and resistant to rice
blast disease. The line PL-21 could be advanced for releasing as variety.
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
IN
PLANT PATHOLOGY
