TITLE:
Root Plate Growth in Sunflower and Its Relevance to Sclerotinia Basal Stalk Rot
AUTHORS:
Christopher G. Misar
KEYWORDS:
Canopy Closure, Inoculation Method, Root Plate Diameter, Sclerotinia Wilt
JOURNAL NAME:
American Journal of Plant Sciences,
Vol.13 No.3,
March
15,
2022
ABSTRACT: Sclerotinia basal stalk rot (BSR) of sunflower (Helianthus
annuus L.) is a fungal disease of the roots that causes symptoms of wilt
and a basal stem lesion. Evaluating root plate growth could improve our
understanding of BSR. Separate studies were conducted to determine the effect
of sunflower growth stage or genotype on root plate diameter in North American
environments. Root plate diameter of cultivated hybrids at reproductive growth
stages was 3 to 4 times larger than vegetative stages. Cultivated hybrids had
larger root plate diameter than interspecific
lines. These results have implications for artificial inoculation methods that
evaluate genotypes for BSR resistance in the field or greenhouse. Disease
escapes can occur if field-grown plants are inoculated too far from the root
plate and/or too early at vegetative growth stages. Side-dressing mycelium-infested cereal
grain closer (i.e., 10 cm) to plants at reproductive growth
stages (i.e., R1 - R4) can increase disease
pressure and reduce disease escapes. These guidelines for the field can be used
to validate results from
artificial inoculations in the greenhouse.