Biology of Colletotrichum truncatum causing anthracnose of soybean and identification of resistant sources
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Date
2022-12-08
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Palampur
Abstract
The present investigation entitled “Biology of Colletotrichum truncatum causing anthracnose of soybean
and identification of resistant sources” was undertaken to study the morpho-cultural characteristics,
standardization of pathogen culture technique, physiological requirements of the pathogen, efficacy of
bioagents, yield loss assessment and evaluation of resistant sources both under field conditions and in vitro
against the pathogen associated with soybean anthracnose. Anthracnose of soybean (Glycine max (L)
Merrill) was found as a major disease in soybean growing areas of Himachal Pradesh with per cent disease
index (PDI) recorded between 17.77 to 46.66 per cent. The pathogen was isolated on PDA and identified
as Colletotrichum truncatum (Schw.) Andrus and Moore based on morpho-cultural characters and
confirmed with molecular characterization. Pure culture of six isolates of C. truncatum from three districts
(Kangra, Mandi and Hamirpur) of Himachal Pradesh were used in present study. In pathogenicity test,
pathogen caused pre-emergence and post-emergence mortality and isolate Ct-3 and Ct-6 was found most
virulent and caused up to 56 per cent pre-emergence and 16 per cent post emergence mortality. Among
seven tested media, PDA (potato dextrose agar) was found best medium for mycelial growth as well as
sporulation of the pathogen at temp. 25±1ºC and pH 7.0. Mathur’s medium was also found suitable for
sporulation of the pathogen. Rapid disease development was observed at ≥ 90 per cent humidity and favours
sporulation of the pathogen. Bio-control agents showed great potential in the management of the disease as
Trichoderma koningii showed good inhibition of the pathogen in dual culture study and also found effective
in improving per cent seedlings stand under glass house conditions. Screening of two hundred germplasm
lines of soybean found 10 resistant and 33 moderately resistant lines under field conditions which were
further screened at seedling as well as on young pods with artificial inoculation. Out of 43 genotypes found
resistant or moderately resistant under field evaluation, two germplasm lines viz. PK 25 and CAT 01 were
found resistant at seedling stage against virulent Colletotrichum truncatum isolate (Ct-3). Four germplasm
lines viz. UPSM 780, AGS 164, PK 472 and PK 25 were found resistant against all the six isolates when
evaluated with young pods inoculation method under lab conditions. Yield loss studies revealed that two
sprays of Propiconazole 25 EC @ 0.1% at full bloom + young pod stage leads to 41.93 per cent avoidable
yield loss as compare to untreated control and was most beneficial in reducing disease severity and
increasing yield over total cost of the fungicidal spray.