Disruptions in the lignin biosynthetic pathway have been shown to reduce disease resistance in
a number of crops. Recently, genetically modified alfalfa (Medicago sativa) varieties have been
marketed with reduced lignin and improved forage quality traits, including increased
digestibility by ruminants at later stages of plant maturity. The objective of this study was
to compare foliar disease resistance in three reference alfalfa varieties, 54R02, DKA43-22RR,
WL355.RR, and the reduced lignin variety, 54HVX41, to evaluate the effect of the reduced lignin
trait on foliar disease resistance. Alfalfa plants in research plots at three locations in
Minnesota were evaluated for percent defoliation caused by foliar pathogens at four maturity
stages; early bud, bud, early flower, and flowering; with natural inoculum. Spring black stem
and leaf spot, Leptosphaerulina leaf spot, and common leaf spot were observed from June through
September in all locations on all varieties. Summer black stem and leaf spot was most prevalent
in August on all varieties at one location. The amount of defoliation increased with maturity
stage for all varieties. When harvest was delayed until the flowering stage, moderate to severe
(32 to 64%) leaf loss occurred, depending on location. Alfalfa varieties did not differ in
percent defoliation at any maturity stage indicating that the reduced lignin trait did not
affect foliar disease resistance.
Poster presentation at the annual meeting of the American Phytopathological Society in August 2018.
Samac, Deborah A; Ao, Samadangla; Dornbusch, Melinda R; Grev, Amanda M; Wells, M Scott; Martinson, Krishona; Sheaffer, Craig C.
Lignin reduction in alfalfa (Medicago sativa) does not affect foliar disease resistance.
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