Sheath rot and its association with discolouration of rice
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Date
2021
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Punjab Agricultural University, Ludhiana
Abstract
The present investigation was undertaken with the objective to find out the association of
pathogens causing grain discolouration and sheath rot of rice and to identify the resistance
sources against sheath rot in rice germplasm. Four pathogens viz., Sarocladium oryzae,
Fusarium verticillioides, Fusarium fujikuroi and Albifimbria terrestris were found associated
with sheath rot and grain discoloration of rice. The fungal pathogens were inoculated on
plants using syringe inoculation, grain insertion method and spray inoculation on 2 varieties,
PR 114 and PR 121. The variety PR 114 was more susceptible to fungal disease as compared
to PR 121. Plants inoculated with grain insertion method showed high disease incidence
followed by syringe inoculation method. Among all the pathogens, S. oryzae caused
maximum per cent disease incidence and severity followed by F. verticillioides, F. fujikuroi
and A. terrestris. The highest disease progress was also observed in plants inoculated with S.
oryzae. All the pathogens produced similar disease symptoms in rice. All the pathogens
caused chaffiness of panicles, significant reduction in seed germination, seedling length and
vigor index was observed in highly infected seeds. The seed quality deterioration was directly
proportional to the intensity of seed infection. Further, the effect of fungal metabolites
extracted from discoloured grains was observed on physiological and biochemical parameters
by dipping seeds in these metabolites for different durations. The seed quality losses were
increased with the increase in duration of seed dipping in fungal metabolites. Significant
reduction in total sugars and total proteins along with an increase in defense related enzymes,
amino acids, proline, total phenols and malondialdehyde content was recorded. Fifty
advanced breeding lines of promising rice germplasm were screened against sheath rot by
inoculating three pathogens S. oryzae, F. verticillioides and F. fujikuroi using two inoculation
techniques (syringe inoculation and grain insertion). Among all the lines evaluated against
sheath rot, RYT 3886 was found to be resistant and RYT 3836 was moderately resistant to all
the three pathogens.
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Citation
Sarbjit Kaur (2021). Sheath rot and its association with discolouration of rice (Unpublished M.Sc. thesis). Punjab Agricultural University, Ludhiana, Punjab, India.