EPIDEMIOLOGY AND MANAGEMENT OF LENTIL DISEASES WITH SPECIAL REFERENCE TO COLLAR ROT DISEASE IN LOWER GANGETIC PLAINS OF WEST BENGAL
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Date
2023-12-20
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PLANT PATHOLOGY, Bidhan Chandra Krishi Viswavidyalaya, Mohanpur, Nadia – 741252
Abstract
Lentil is one of the oldest known protein-rich grain legumes in the winter cropping system of Indo-Gangetic plains including lower Gangetic Bengal (LGB) and provides a balanced diet with high nutritional value. Lentil productivity in this zone is seriously impeded due to the prevalence of several biotic stresses. Collar rot, lentil blight complex (LBC) and rust are major problems for lentil not only in Eastern India, but throughout the South Asia. Collar rot disease incited by Sclerotium rolfsii Sacc. is one of the most dreaded soil borne diseases of lentil and is found to cause yield losses of up to 50% in the farmer’s field (Asghar et al., 2018). Most importantly there is no resistant genotype of the lentil crop against collar rot disease and chemical control is not also effective against this soil borne disease. In the present investigation, a comprehensive effort has been made to study the disease situation of different diseases of lentil under lower Gangetic plains of West Bengal; screening and
identifying promising stable tolerant lentil genotypes against major diseases of lentil under
field conditions, developing a forewarning model for successful prediction of collar rot
disease and development of biorational management package utilizing plant extracts,
bioagents, inducers and chemical fungicides for efficient eco-friendly management of S.
rolfsii inciting collar rot disease of lentil.
Thus, taking a holistic view on all these aspects, an intensive survey was conducted in major
lentil growing districts of West Bengal, viz. Nadia, North 24 Paraganas, Malda and
Murshidabad in the months of November–March (2018-19, 2019-20 and 2020–21).The
present survey study reflected that lentil fields were infected with three main fungal diseases:
Collar rot (Sclerotium rolfsii), lentil blight complex (LBC) and rust (Uromyces viciae-fabae)
disease. Collar rot and LBC were the most widespread, while lentil rust occurred little
comparatively to both diseases. There was no individual occurrence of either Alternaria or
Stemphylium blight rather mixed infection was obtained in a complex manner. To the best of
our knowledge, this is the first report of mixed infection of A. alternata and S. botryosum in a
complex manner followed by successful isolation of S. botyrosum and confirmation of the
pathogens by sequencing through ITS and Stemphylium specific gpd1 and gpd2 primers.
Higher disease response was observed in normal sown fields for collar rot disease whereas
for lentil blight and rust, the highest disease severity was observed in late sown fields.
Ensuring lentil planting during the second fortnight of November can mitigate the climate
mediated disease risk. Soil texture played a significant role in the collar rot development,
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more pronounced in light textured soil. Intercropping with mustard and okra individually
considerably reduced the DI for collar rot disease as compared to other intercropping
patterns. For collar rot disease, ILL-10802 was observed as highly tolerant with only 2% DI
and HUL-57 as highly susceptible with 34.7% DI. For blight and rust diseases, the highly
tolerant varieties were Pusa ageti (DS 5.4%) and IPL-526 (DS 3.2%) respectively, whereas
local varieties were susceptible to both diseases.
Screening of lentil genotypes for resistance against collar rot (Sclerotium rolfsii) reflected
that the effect of genotype, environment and the genotype environment interaction (GEI)
were significant among the tested lentil genotypes albeit G (genotypes) found to exert a
greater effect compared to the environment in this variation. Among the locations, the highest
mean collar rot disease incidence irrespective of genotypes (including check) over 3 years
was observed in Chakdah location (19.18%) followed by Kalyani location (16.46%), whereas
the lowest mean incidence was observed in Sekhampur location (13.84%). Amid the
genotypes, the significantly lowest average collar rot disease incidence (2.26%) was observed
in WBL-58 followed by IPL-603, PL-254, X2012S-186-S20 and TCADL-18-2. From the
GGE biplot for resistance against collar rot (Sclerotium rolfsii), PL-254 was considered as the
"ideal" genotype and WBL-58 and IPL-603 were recognized as "desirable" genotypes with
coherent response over the tested locations. Over the years, Sekhampur location displayed
closest angle with "AEC abscissa," than the other 2 locations thus being identified as
"representative". Therefore, Sekhampur location with the highest desirability index (4.264)
was considered as the “ideal location” for screening against collar rot in lentil. Chakdah
location and Sekhampur location were grouped in upper mega environment and Kalyani
location during both the years grouped in the lower mega environment. In upper mega
environment ME- I, IPL-603 was the only best performing genotype and in ME- II, WBL-58
and X2012S-186-S20 were the winning genotypes but in comparison to X2012S-186-S20,
WBL-58 genotype exhibited high stability.
Screening of lentil genotypes for resistance against lentil blight complex (LBC)
(Alternaria/Stemphylium) reflected that the effect of genotype, environment and the genotype
environment interaction (GEI) were significant among the tested lentil genotypes although, G
(genotypes) contributed higher in comparison to the environment in this total variation.
Among the locations, the highest mean LBC disease severity irrespective of genotypes
(including check) over 3 years was observed in Chakdah (23.84%) followed by Kalyani
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(20.08%), whereas the lowest mean severity was observed in Sekhampur (16.08%). Amid the
genotypes, the significantly lowest average LBC disease severity (9.49%) was observed in
IPL-239 followed by PL-7, DPL-62, TCADL-19-5 and BCL-1296. From the GGE biplot for
resistance against lentil blight complex (LBC) (Alternaria/Stemphylium), DPL-62 was the
"ideal" genotype and TCADL-19-5 followed by BCL-1296 were recognized as "desirable"
genotypes. Kalyani location with the highest desirability index (4.252) was considered as the
"ideal" location for screening against LBC disease severity in lentil.
Stepwise multiple regression analysis (MRA) and canonical discriminate model could predict
only 51.9% and 71.7% respectively of the variations of S. rolfsii disease incidence. Among
the different prediction models, Binary logistic regression model was found to be the most
sensitive model and successfully predicted 77.8% of disease risk and no-risk periods in the
testing data set. Among the thirteen soil abiotic factors and weather variables examined,
((Soil TM(5cm), Soil TM(15cm), Soil TM(30cm), Soil TE(5cm) and Soil TE(30cm)) were found
to be the significant parameters in predicting disease occurrence in the binary logistic
regression model.
Biochemical parameters phenol, antioxidant enzymes PPO, PAL and SOD were found to be
significantly negatively correlated with collar rot disease incidence indicating that these
enzyme activities might play a major role in attributing resistance towards host-pathogen
interactions. In the field experiment, it was observed that the seed and soil treatment with
microbial consortia (GP8: Pseudomonas aeruginosa and B11: Bacillus subtilis) and conjoint
application of chitosan (seed treatment) and Ageratum plant extract (soil drenching) checked both pre and post emergence damping off/ collar rot disease of lentil and enhanced the yield of lentil. Thus, this bio-intensive disease management package may in the future be used in a large scale in this zone for cheap and eco-friendly management of soil borne diseases in different cropping systems.