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A total of
400 accessions of the wild sunflower Helianthus maximiliani and
Helianthus nuttallii were tested for their reaction to basal
stalk rot caused by Sclerotinia sclerotiorum under field
conditions at the Morden Research Station of Agriculture and Agri-Food
Canada. This was studied over a four-year period (2000-2003). The
accessions were grown in small hills and were artificially inoculated
with sclerotinia-infected millet seed applied at 1-2 cm below soil
surface adjacent to the stems of sunflower plants at the seedling
stage. Fifty-four 54 accessions were identified with resistance to
sclerotinia basal-stalk infections with consistent results over the
four-year period.
The reactions of 48 accessions
of H. maximiliani and 48 accessions of H. nuttallii to
sclerotinia head rot infections were studied in 2002 and 2003. Plants
were artificially inoculated at different growth stages with different
forms of sclerotinia inoculum including ascospores, fresh mycelia and
ground sclerotinia infected millet seed, and covered with paper, plastic
and pollinating bags. The ground sclerotinia infected millet seed in
combination with paper bag covers was the most effective method to
produce disease epidemics, followed by ascospores with paper bag
covers. Fifteen 15 accessions were identified with no head or mid-stem
infections over the two-year period.
This study demonstrated the
presence of resistance to Sclerotinia infections in wild sunflower
species. Future research will concentrate on studying the genetics of
this type of resistance, and on transferring the resistance gene(s) into
H. Annuus and into commercial sunflower hybrids.
Acknowledgements:
This project was made possible
by funding from the Governments of Manitoba and Canada through the
Canada-Manitoba Agri-Food Research Development Initiative (ARDI.
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