PhD

The study entitled 'Epidemiology and management of false smut of rice
(Oryza saliva L.) in Kerala' was conducted during the period 2010-2013 at College
of Agriculture, Vellayani, Trivandrum and the field experiments and varietal
evaluation trials were carried out at the Regional Agricultural Research Station,
Pattambi, Palakkad, Rice Research Station, Moncompu, Alappuzha and at Farmers
fields at Vilayur (Palakkad) and Chambakkulam (Alappuzha).
The results of the surveys conducted at Alappuzha and Palakkad indicated
that maximum disease was observed at the upper Kuttanad area of Alappuzha. A new
collateral host for the pathogen, Oryza spontaneum was observed at Alappuzha
during the survey. Isolation of the pathogen was made from the samples collected
during the survey. The method of isolation of the pathogen was standardized. Surface
sterilization of smut balls with 0.1 % HgCb for 3.5-4 minutes followed by three serial
washings with sterile water and dusting of the chlamydospores over YPPDA, and
pure culturing after observation under a light microscope after 24 hrs was the method
devised for isolation. Ideal conditions for culturing of the fungus under in vitro
conditions were found to be the use of YPPDA medium of pH 6.5 at 28°C under full
darkness. An indigenous medium viz., rice extract sucrose agar was developed for the
culturing of the pathogen.
The pathogen, Ustilaginoidea virens was observed to be producing smut balls
and chlamydospores in culture similar to that produced under field conditions.
Stromatic heads of the fungus was observed under in vitro conditions for the first
time in India. Sequencing of the ITS region of pathogen gave 100% similarity with
the known sequences of U. virens on BLAST analysis and thus the pathogen was
conformed to be U. virens. The pathogen isolates were identified and deposited at
ITCC, New Delhi, and the accession numbers ITCC-7335 (Pattambi, Palakkad) and
ITCC-7334 (Moncompu, Alappuzha)were obtained for the isolates.

Laboratory trials revealed the efficacy of five chemical fungicides, different
species of Trichoderma and three bacterial strains for suppression of the pathogen in
vitro.
Correlation studies on the influence of weather parameters on the
development of the disease revealed that the disease was negatively correlated with
the minimum temperature during SO % flowering. Results of the survival studies of
the pathogen revealed that the smut balls of the pathogen can survive for eight
months at room temperature. At field level, the fungus was found to be surviving on
the ratoon rice emerged from the stubbles of the previous crop.
Under the varietal evaluation trials conducted at Alappuzha and Palakkad, the
varieties Vaishak and Harsha were found resistant to the disease and the varieties
PTB 10 and Makom were moderately resistant. The varieties, Uma, Remanika, Gouri
and Bhagya were the most susceptible ones. RAPD profiling of the resistant and
susceptible varieties with 10 random primers showed polymorphism with five
primers OPK-I4, OPG-I8, OPC-IS, OPB-IO and OPD-I8.
Field trials conducted at Alappuzha and Palakkad showed that spraying of
Propiconazole 12Sg a.i./7 SO L or TebuconazoleO.I87 S kg a.i./SOO L or Copper
Hydroxidel000 g a.i./7S0 L or Pseudomonas flourescens @ 2% of the talc based
formulationat SO% flowering could control the disease effectively. Tebuconazole
0.187S kg a.i./SOO L gave significant yield increase over the control.
Biochemical studies like SDS PAGE and NA TIVE PAGE were conducted.
SDS PAGE showed conspicuous bands of the pathogen proteins and NATIVE PAGE
revealed increased activity of peroxidase and polyphenol oxidase on the diseased
grams.
Based on the research results, a management package was developed for
effective control of the disease at the field level as follows: 1) avoiding use of paddy
grains harvested from severely affected fields as seed material 2) avoiding continuous

cultivation of the most susceptible rice varieties like, Uma, Remanika, Gouri and
Bhagya 3) use of resistant varieties like Harsha, Vaishak or Makom 4) Weed
management to control the collateral hosts like wild rice 5) biological control by
spraying of Pseudomonas flourescens @ 2% of the talc based formulation at 50%
flowering 6) spraying of Propiconazole125 g a.i./750 L or Tebuconazole 0.1875 kg
a.i./500 L or Copper Hydroxide 1000 g a.i./750 L at 50% flowering.