Epidemiological modelling and eco-friendly management of rice blast
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Date
2023-12-20
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Plant Pathology, Bidhan Chandra Krishi Viswavidyalaya, Mohanpur, Nadia – 741252
Abstract
Rice generally grown in different agro-climatic situations in every continent although its
productivity is generally affected by numerous abiotic and biotic stresses. Among all the biotic
stresses, rice blast caused by Magnapothae oryzae B. Couch (anamorph Pyricularia oryzae
Cavara) is one of the most harmful fungal disease that leads to grain yield losses up to 70 to
80%. Several environmental factors including temperature, rainfall, humidity has immense
contribution for the disease development, infection rate and spread of the disease. Rapid
climatic changes along with increasing global warming is contributing in spreading of the rice
blast disease in other part of the world where rice is growing regularly. Increasing harmful
effect of chemical fungicide causing serious damage to environment and as well as non-target
organism during chemical management practices. A sound management strategy compiling the
identification of novel resistance gene in different cultivars, use of bio antagonist, alteration of
planting date, use of elicitors can be considered as the effective and as well as sustainable
approach for combating against this disease. As belonging to the most important rice grown
areas, eastern region (especially West Bengal), should come upon in the top of the priority list
where the forecasting system can be developed and can be applied for or combating rice blast
disease.
Keeping all these in mind, the objectives of the present studies are as mentioned bellow:
1) To identify the critical key factors responsible for rice blast disease development in field
condition and pathogen development in lab condition.
2)To develop spatial and temporal model of rice blast for eastern region.
3)To develop eco-friendly and non-conventional way of management for rice blast.
A survey was conducted for getting idea about the disease prevalence in some rice growing
districts of West Bengal in 2018, Rabi season and it was observed that highest disease severity
was noticed in West Midnapur (41.67%) on Satabdi variety and minimum was in North 24
Pargana (10.00%) on Lal minikit variety. In invitro condition in different growth medium PDA
produced maximum growth (89.00mm) and sporulation (18.00/10 μl) of P.oryzae and
minimum growth was in Czepk Dox Agar(30.33mm) whereas, least sporulation was in Carrot
Dextrose Agar medium(0.33/10 μl). Among the different carbon sources used in media, the
highest growth was in Dextrose (89.33mm), sporulation (17.67/10 μl) and least was in fructose
(48.33mm), sporulation (1.33/10 μl). Among the Nitrogen sources used in media the growth
and sporulation of the pathogen was highest in Potassium Nitrate (64.33mm and 11.33/10 μl
respectively), and least was in ammonium nitrate (38.33mm growth and 1.33/10 μl sporulation
respectively). Highest mycelium growth(89.00mm) and sporulation (17.33/10 μl) was obtained
at 25˚C temperature and lowest was observed in 35 ˚C (8.00mm) and no sporulation occurred.
Maximum hyphal growth was obtained in pH 6.0(89.00mm) and minimum was in pH
10(22.67mm). Highest number of blast lesion (12.00) was observed at 8 hours of leaf wetness
in 25˚C and lowest number of lesion (0.33) was observed in 20˚C in two hours of leaf wetness.
For the yield loss estimation different number of sprayings of Tricyclazole 75WP @0.1% were
used and found that minimum PDI was recorded in staggered spraying i.e. 12.59% followed
by 4 no. spraying (27.59%) at 75 DAT. The linear regression model showed that with every
1% increase in disease severity there is significant decrease in grain yield of 0.079 q/ha in
pooled mean of both the years.
To know about the effect of different date of transplanting on rice blast disease severity,
three varieties (Satabdi, Khitish and Gontro Bidhan 3) were transplanted in three different date
of transplanting (16th January,1st February and 15th February) in two places (Jaguli, Nadia and
Jalangi, Murshidabad). In Jaguli the maximum PDI was recorded in the crop transplanted on
16th January (35.74%) and minimum in 15th February (27.09%) in pooled mean. Whereas, the
minimum PDI was recorded in Khitish (18.45%) and maximum in Satabdi (47.22%) in pooled
mean. In Jalangi, the maximum PDI was recorded in the crop transplanted on 16th (26.54%)
and minimum in 1st February (D2) (20.86%) pooled mean. Whereas, the minimum PDI was
recorded in Khitish (14.01%) and maximum in Satabdi (35.37%) in pooled mean. Among the
diseases forecasting models i.e. observed, Gompertz and Logistic, Gormpertz fit better as
compare to rest two irrespective of date of sowing and varieties, that was confirmed by highest
R2 and low Standard error.
To find out the eco-friendly and non-conventional way of rice blast disease
development, bio control agents tested against Pyricularia grisea among which T.harzianum
showed highest percentage of inhibition in Radial Growth (PIRG) (43.57%) at 96 hours after
inoculation (hai) and the minimum PIRG was in case of Pseudomonas fluorescence (20.88%)
at and 96 hai. Among the 50 varieties used for the screening of rice blast disease, 21 Varieties
showed Resistance(R),16 were moderate resistant (MR),7 were moderately Susceptible (MS),
3 were Susceptible and only 3 were highly resistance nature (HR). The biochemical assay of
three different rice varieties was done by the use of three different inducers viz. Salicylic
Acid(SA), Jasmonic Acid(JA) and Benzothiadizole (BTH) as seed treatment under three
different concentrations. It was observed that PAL activity reduced significantly in 48 hpi in
comparison to 24 hpi and then gradually increased at 72 hpi irrespective of inducers and their
doses. The PAL activity was highest in resistance variety Khitish and minimum in susceptible
variety Satabdi. The POD activity was increased with the increase in time whereas in non-
inoculated set in all cases the POD reduced at 48 hpi in comparison to 24 hpi and then gradually
increased at 72 hpi. In field condition most effective treatment was Seed treatment with
T.harzianum + Soil treatment with Bacillus subtilis with minimum PDI(19.44%), Whereas Soil
treatment with Bacillus subtilis(T3) showed maximum PDI(39.25%) In the integrated approach
of inducer and fungicide application, the highest PDI(38.70%) was recorded in Seedling
treatment with BTH Whereas, the lowest PDI(23.15%) was recorded in Seedling treatment of
SA+one spray of SA (tillering stage) +one spray of Tricyclazole 75WP@0.1% (boot leaf
stage).