Epidemiology and integrated management of potato wilt caused by sclerotium rolfsii sacc.
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Date
2007
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UAS Dharwad
Abstract
The sclerotium wilt /rot caused by Sclerotium rolfsii Sacc. is one of the major soil
borne diseases of potato causing heavy losses every year. The incidence of wilt was noticed
in all locations surveyed with a range of 1.50 to 12.40 per cent and incidence of rot ranged
from 2.00 to 16.25 per cent. The maximum incidence of wilt was noticed in Belgaum
(7.25%) and least in Bidar (2.50) districts. The rot incidence was more in Dharwad (9.51%)
less in Bidar (5.72%) districts.
Four per cent inoculum level was sufficient to cause 100 per cent infection. The
maximum per cent germination of sclerotium (87.50%) was noticed at 1 cm depth, which
gradually reduced with increase in depth. The germination of sclerotium was 100 per cent up
to one month after storage and decreased gradually with increase in storage duration. The rate
of movement of mycelia at low inoculum level (one sclerotium) took eight days to cover 9
cm distance, but higher inoculum (five sclerotia) took 6 days to reach the same. Colonization
of sorghum seeds and germination of sclerotia were drastically reduced with increase in EC
levels. Growth of the pathogen was maximum at the temperature of 25-300C, soil moisture of
30 per cent and pH of 5.5 to 9.0.
The results of morphological and cultural studies indicated that there was slight
variation among ten isolates. RAPD data distinguished isolates in to two major clusters A and
B. The results revealed that, geographical locations of isolates were closely related. All 12
hosts were found susceptible. Among 63 genotypes screened only 3 genotypes showed less
than 4 per cent incidence.
IDM experiments conducted in farmers fields revealed that, maximum suppression of
the disease was observed when carboxin (2g kg-1) and Trichoderma harzianum were used for
tuber treatment and supplemented with either FYM or vermicompost. The highest total return
and additional return over control were obtained in carboxin + T. harzianum + FYM
treatment. There was a gradual increase in population of both T. harzianum and T. viride over
the two years in all locations. The competitive saprophytic ability (CSA) of pathogen was
found to decrease over the years. The B: C ratio of IDM trials in farmer’s fields showed
above 3 for both the years in all the locations.
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Keywords
Plant Pathology