STUDIES ON EARLY BLIGHT OF POTATO CAUSED BY Alternaria solani (Ellis and Martin) Jones and Grout
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Date
2016-01-29
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UNIVERSITY OF AGRICULTURAL SCIENCES GKVK, BENGALURU
Abstract
Potato is one of the most important staple food crops, ranking fifth and fourth
place in area and production in the world, respectively. Among various diseases,
Alternaria leaf spot is one of the most destructive disease on potato. Cultural studies
revealed that, the growth of the pathogen was maximum on solid Potato Dextrose Agar
medium (78.11 mm) and maximum fungal dry matter (188 mg) was observed in Potato
Dextrose broth medium. The favourable temperature for the growth of the fungus was
range between 30 ºC to 35 ºC. The maximum mycelial dry weight obtained at pH 6.0
(157 mg) to 6.5 (152 mg). In vitro evaluation of fungicides revealed that, the fungicide
Tebuconazole (100 %), Hexaconazole+Zineb (95.18 %) and Trifloxystrobin+
Tebuconazole (88.15 %) inhibited pathogen growth at 1000 ppm concentrations. T.viride
IIHR-21 (69.63 %) and T.viride IIHR-22 (66.30 %) were found effective against A.
solani. The crude leaf extracts from nine plants (Calotropis, Lantana, and Lemon grass,
Nagadhale, Neem, Pongamia, Simarouba, Subabul and Tulasi) were tested against A.
solani and found that Simarouba leaf extract (54.44 % at 1:1 dilution ) showed maximum
inhibition of the pathogen. Under glass house condition Tebuconazole (48.33 % at 90
days) reduced disease severity and increased yield in Potato. The field evaluation
offungicides, bioagents and sea weed extracts indicated that Mancozeb @ 0.2 % >
Hexaconazole+Zineb @ 0.2% > Tebuconazole @ 0.1 % > Metalaxyl+ Mancozeb @
0.2% > Tebuconazole+ Trifloxystrobin @ 0.1 % > Fenamidone+Mancozeb @ 0.2 %
most effective in reducing severity (36.63 % at 90 days) of the early blight disease and
increasing tuber yield (61.33 Kg/plot). In untreated check the disease severity was 83.03
per cent with plot yield of 32.66 kg. The foliar spray of fungicide combination is useful in
the better management of early blight of potato.
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