Epidemiology of turcicum leaf blight in maize and identification of resistance sources
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Date
2021-09-08
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Palampur
Abstract
Investigations on turcicum leaf blight of maize were undertaken with the objectives to study the role of
environmental factors on disease development and identify resistance sources for turcicum leaf blight.
The pathogen on PDA revealed grayish to blackish, fluffy growth. The conidia were cylindrical or
straight, 3-8 septate with length varied from 81µm to 96 µm and width ranged from 18 to 24 µm.
Maximum mycelial growth and sporulation of Exserohilum turcicum was observed on Oat Meal Agar
The minimum mycelial growth was observed in V8 Juice. Age of the plants has got significant effect
on the extent of susceptibility. Plants of all age groups were found to be infected by E. turcicum, but
severity differed significantly with the age of plant. Significantly higher turcicum leaf blight infection
was recorded on plant age group of 60 days. Maximum spore germination (90.43%) was recorded after
36 hr of incubation period. Maximum disease progression rate was observed during 35th MSW in Early
Composite (20.5) and Dhari Local (20.4), whereas it was 10.7 in Bajaura Makka during 31st MSW.
Disease intensity showed positive correlation with the maximum temperature and maximum relative
humidity. Negative correlation was observed with minimum temperature minimum relative humidity
and rainfall. The multiple correlation coefficients were highest in Early composite and Dhari Local
(0.91), whereas, it was 0.89 in Bajaura Makka. The coefficient of multiple determinations indicated
that relative humidity (maximum and minimum), temperature (maximum and minimum) and rainfall
were responsible for 0.79 to 0.83 variations in disease intensity among different varieties. A total of
fifty five maize inbreds comprising of twenty six medium maturity, twenty two early maturity and
seven QPM along with two susceptible checks Dhari Local and Early Composite were screened against
E. turcicum under artificially inoculated conditions. Fourteen medium maturity, fourteen early maturity
and seven QPM inbreds were found resistant to TLB. Crude extract of Eucalyptus resulted in the
highest mycelial growth inhibition at 10, 20 and 30 per cent concentration, where as crude extract of
Allium sativum was found least effective at all the concentrations. In vitro evaluation of bioagent
revealed that maximum mycelial inhibition (78.8 %) recorded in Trichoderma koningii (JMA-11) The
crop loss estimation trials due to turcicum leaf blight revealed that loss in grain yield varied from 5.2 to
27.2 per cent depending upon the disease severity and level of resistance/susceptibility in different
genotypes. Dhari Local recorded maximum yield loss (27.2%) followed by Early Composite (25.3%).
Similar loss trends were observed in other yield attributing characters.