National Academy of Agricultural Sciences (NAAS)
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PRINT ISSN : 2319-7692
Online ISSN : 2319-7706 Issues : 12 per year Publisher : Excellent Publishers Email : editorijcmas@gmail.com / submit@ijcmas.com Editor-in-chief: Dr.M.Prakash Index Copernicus ICV 2018: 95.39 NAAS RATING 2020: 5.38 |
Downy mildew of onion is one of the major threats to onion cultivation, especially in sub-tropical and dry temperate zone, caused by an oomycetes Peronospora destructor (Berk.) Casp. ex Berk. A study was undertaken to investigate into the epidemiological factors that affects the initiation and dispersal of disease. Under in vitro conditions suitability of different temperature and relative humidity regimes, on germination and relative growth of germ tube has been studied. The pathogen preferred a temperature of 15°C as optimum for sporangial germination where the favourable relative humidity was above 95.1 per cent with maximum sporangial germination at 100 per cent. Correspondingly the effect of different meteorological parameters on the appearance and dispersal of the disease were also studied. The maximum temperature, ranging between 21.45 to 26.6 ℃ and minimum temperature in the range of 7.6 to 18.2 ℃ were positively and significantly correlated, where average relative humidity was positively correlated but not significantly. Cumulative rainfall was found negatively correlated showing that rainfall has no specific role in epidemic development. Disease initiated when favourable conditions like temperature and relative humidity prevailed for at least two days.
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