STUDIES ON BACTERIAL LEAF BLIGHT OF RICE CAUSED BY Xanthomonas campestris pv oryzae (Uyeda and lshiyama, Dowson) Dye
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Date
1988
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ACHARYA N.G. RANGA AGRICULTURAL UNIVERSITY, RAJENDRANAGAR, HYDERABAD
Abstract
Bacterial leaf blight of rice caused by
Xanthomonas campestris pv oryzae (Uyeda and
Ishiyama, Dawson) Dye. is a severe disease on
high yielding rice cultivars. Symptom!? appeared
as water soaked lesions from the - cut ends of
leaves after two days of lnocul1ation. The lesions
extended on both the sides of leaves and turned
orange yellow. A.f ter 14 Elays of inoculation the
lesions extended and tne ..leaves turned to yellowis.h
white. A characteristic wavy margin was observed .
between the healthy and diseased leaf~ portions •
Among the 52 rice c~ (h\IQYS screened
against BLB, 5 cul ti vars showed resistant
reaction, while 20 cultivars were moderately
res is t,au t, 19 cu 1 t, l vars we rc modt!t'a Lc ly au:w f:-
ptible and the r emaining 8 cultivars were
highly susceptible.
Rate of spread of the disease was studied
in BJ 1 , IR 20 and T { N) 1 , which indica ted that
in ·esistant BJ 1 the spread of the pathogen
was very much . restricted and in suscept~bl~ T{N) 1
·The pathogen could spread to a longer lear area~
These 52 rice cultiv~rs were'~n~ooui~ted at
three different ages of crop ·growth in order
to study the effect of crop age on disease incidence.
Varieties BJ 1 and DV 85 showed resistant
reaction at all the three stages or inoculation,
while IR 62 showed resistance at 30 days after
sowing and MTU 6861 and _Wgl 22245 sh~wed resistance
at . . .60 days a.f..t er sowing and remaining ~. arieties
developed resistance with plant age.
Studies on changes in biochemical constituents
of susceptible and resistant varieties
following BLB infection indicated that healthy
leaves of BJ 1 and IR 20 contained more sugars
than healthy leaves. of RNR 1446 and T{N)1. The
level of total sugars decreased in diseased leaves
of all the 4 varieties but the decrease was more
in T(N)1 and RNR 1446.
Amino acids were more in highly susceptible
and suceptible varieties than in resistant and
moderately resistant varieties. The amino acid
content was · increased in diseased leaves of T(N)1
and RNR 1446 but decreased in BJ 1 and IR 20.phenolsand
The increase in OD phenols and total
was more aft.cr inoculation in BJ 1, IRto
RNR 1446 and least in T(N)1. Healthy
l eaves of resistant varieties had more quant.itles
of OD phenols and total phenols than the susceptible
varieties.
Slow releasing nitrogenous fertilizers
showed a marked effect on severity of BLB on
T ( N) 1. Among the three slow releasing nitrogenous
fertilizers urea super granules had a considerable
effect which not only increased disease score,
plant height but also number of tillers. A combination
of N, P and K showed a good effect on
T(N) 1, with a least disease score, proper plant
height and number of tillers when compared to
individual treatments of N, P and K.
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Keywords
STUDIES, BACTERIAL, LEAF, BLIGHT, RICE, CAUSED, Xanthomonas, campestris,