STUDIES ON Alternaria BLIGHT OF SUNFLOWER
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Date
2017-08-23
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UNIVERSITY OF AGRICULTURAL SCIENCES GKVK, BENGALURU
Abstract
Sunflower is an important oilseed crop of India. The crop suffers from many
diseases of which Alternaria leaf blight is important. Alternaria helianthi was isolated
from the leaf samples collected during kharif, rabi and summer. In all the three seasons
mixed infection of A. helianthi and A. alternata was observed. Cultural studies revealed
that highest radial growth was observed on Richard’s and potato dextrose agar, but
profuse sporulation was in host leaf extract + sucrose and host leaf agar. Maltose and
potassium nitrate were the best carbon and nitrogen sources respectively that showed
maximum growth. Profuse sporulation was noticed in case of sucrose and glucose as
carbon sources whereas potassium nitrate was ideal nitrogen source. Physiological
studies revealed 25oC as the optimum temperature for growth whereas slightly acidic pH
(6-7) showed maximum mycelial dry weight of A. helianthi. The PCR amplification and
sequencing of ITS rDNA region confirmed both A. helianthi and A. alternata as the cause
of leaf blight. Among the combi fungicides Propiconazole + Difenoconazole at 0.1 per
cent; systemic fungicide Azoxystrobin and Propiconazole at 0.075 and 0.1 per cent; nano
molecules silver colloidal particles at 250 ppm were found to be superior in inhibiting
growth. Screening of nine AHT and seventeen IHT coordinated trial entries of sunflower
genotypes against Alternaria helianthi under natural field conditions revealed that, seven
entries were moderately resistant while all other entries were found susceptible to
Alternaria leaf blight.
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