Role of seed borne inoculum on karnal bunt infection risks

Abstract

Field studies on the role of seed borne inoculum of Karnal bunt (KB)
and infection risks were carried out at Punjab Agricultural University,
Ludhiana during 2003-04 to 2011-12 using the most susceptible wheat
variety, WH 542. The potential of KB infected seeds in causing the
disease in subsequent years was determined by planting seed of
different KB intensities (0.0 -10%) at different sites. The KB continued
to appear up to five years in three of the sites, though in traces in
some of the seasons. Weather conditions played a significant role
in the disease development. Nevertheless, the pattern of disease
occurrence was often independent of different KB intensities due to
lateral movement of infective propagules across the plots. Occurrence
of infection may have depended more on wind direction, random
movement and chance landing of sporidia. Another study conducted
from 2005-06 to 2007- 08 showed that disease occurred up to 100 m from
the primary inoculum centre. In third experiment the disease incidence
was observed to be comparatively higher when the bunted grains were
powdered and applied at the soil surface than when used as whole
grains beneath the soil. Even a single powdered infected grain, was
capable of causing considerable infection around 10 m radius. The
fourth and fifth experiments (2006-07 to 2007-08), respectively, carried
out to ascertain the viability of sporidia in relation to nutritional
component and field exposure showed that sporidia maintained their
viability, respectively, for 21, 18 and 9 days in January, February and
March under field conditions and also on soil extract and leaf washing
agar up to 4th sub-culturing indicating their potential to survive and
travel long distances.