Biology of Alternaria cyamopsidis and Bioefficacy of Botanicals against Alternaria Blight, Powdery Mildew and Bacterial Leaf Blight of Organic Cluster Bean (Cyamopsis tetragonaloba L.)
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Date
2021
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MPUAT, Udaipur
Abstract
The present investigation was undertaken to study scenario and distribution of
A. cyamopsidis in cluster bean growing areas, morphological, cultural and pathogenic
variability in isolates of A. cyamopsidis, effect of temperature and H ion concentration
on growth and sporulation of A. cyamopsidis, yield loss assessment caused by
complex of Alternaria blight, powdery mildew and bacterial leaf blight diseases and
effective management of the disease complex through organic practices.
Surveys of Alternaria blight disease intensity in cluster bean during Kharif
2015 and 2016 at Udaipur, Chittorgarh, Ajmer and Jaipur districts of Rajasthan
showed that mean PDI was maximum in Udaipur district (20.62 and 25.39 at
flowering stage and 28.33 and 29.32 per cent at pod formation stage), while in Jaipur
district (15.91 and 17.30 per cent at flowering stage and 21.63 and 21.26 per cent at
pod formation stage), the mean PDI was lowest.
The cultures of A. cyamopsidis and X. axonopodispv. cyamopsidis species
were isolated, purified and identified under the microscope through morphological
characters of the respective pathogen. The isolates of A. cyamopsidis (Ac1 (RCA),
Ac2 (UDP 1), Ac3 (UDP 2), Ac4 (CH), Ac5 (AJM) and Ac6 (JPR) collected from six
different locations of Udaipur, Chittorgarh, Ajmer and Jaipur districts exhibited
considerable variations in symptoms on inoculation on pot-grown plants and also in
colony diameter, size, colour of the colony and rate of growth and sporulation on
PDA medium.
Among the isolates of A. cyamopsidis, shortest latent period (36.00 hrs) was
recorded in Ac1 (RCA), while it was maximum in Ac6 (JPR) isolate (55.00 hrs).
Significantly maximum PDI (65.3) was also observed with the isolate Ac1 (RCA) and
minimum (38.6) with isolate Ac6 (JPR). In physiological studies, it was found that the most virulent isolate Ac1 (RCA)
of A. cyamopsidis could grow on wide range of pH from 4.0 to 8.0. Though, pH 3.0
and 3.5 did not support the growth. It was observed that pH 6.5 is optimum for the
growth of test fungus, A. cyamopsidis which yielded significantly highest dry
mycelial weight (286.90 mg). On incubation of A. cyamopsidis at different
temperature levels, least radial growth (13.55 mm) was recorded at 10 °C, while it
was maximum (86.48 mm) when incubated at 25 °C for 7 days.
While assessing losses, pooled data of the two years suggested that organically
protected mixed inoculated control plots had minimum PDI of 15.3 and 21.3 for A.
cyamopsidis, 22.1 and 23.4 PDI for X. axonopodis pv. cyamopsidis and 18.05 and
22.85 PDI for powdery mildew. Though, inoculated unprotected plots exhibited
significantly highest PDI for the respective pathogens. Significantly highest yield of
677 g/plot was observed in organically protected mixed inoculated control plots. It
was followed by plots with naturally infected powdery mildew (520 g) and plots
inoculated by X. axonopodis pv. cyamopsidis (504 g).Lowest seed yield of 481 g per
plot was recorded in the plots inoculated with A. cyamopsidis. The reduction in yield
of 28.89, 25.45 and 23.09 per cent was observed with A. cyamopsidis, X. axonopodis
pv. cyamopsidis and L. taurica when compared to organically protected plots.
In the present management studies under natural infection in field revealed
that among tested organic practices, neem oil was found to be most effective in
managing all the three diseases and also giving maximum seed yield, followed by
neem leaf extract, panchgavya and garlic bulb extract. Following the order, basil
treatment was found next with moderate efficacy and Indian aloe treatment was least
effective. However, all the organic treatments suppressed all three diseases
successfully over absolute control.Among the tested concentrations of these organic
inputs. Higher concentration was most effective, however, it was at par with optimum
concentration. Lower concentration was found significantly least effective.Results of
various yield attributes studied for each treatment as well as concentrations level also
indicated that neem oil treatment was best in relation with maximum plant height,
pods per plant, seeds per pod, seed index, plant population and seed yield. However,
seeds per pod and plant population per meter row length did not differ significantly
among the organic treatments.
Description
Biology of Alternaria cyamopsidis and Bioefficacy of Botanicals against Alternaria Blight, Powdery Mildew and Bacterial Leaf Blight of Organic Cluster Bean (Cyamopsis tetragonaloba L.)
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Citation
Rani V. And Trivedi A.