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ARS Home » Midwest Area » St. Paul, Minnesota » Plant Science Research » Research » Publications at this Location » Publication #347588

Title: Modification of lignin in alfalfa does not affect foliar disease resistance

item Samac, Deborah - Debby
item AO, SAMADANGLA - University Of Minnesota
item Dornbusch, Melinda - Mindy
item GREV, AMANDA - University Of Minnesota
item WELLS, M SCOTT - University Of Minnesota
item MARTINSEN, KRISHONA - University Of Minnesota
item SHEAFFER, CRAIG - University Of Minnesota

Submitted to: Forage Focus
Publication Type: Trade Journal
Publication Acceptance Date: 11/15/2017
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Lignin is well known for its function in plant stems to reinforce cells walls to reduce lodging and for its negative impact on digestibility of forages by ruminants. Lignin also in known to play a role in disease resistance by forming a barrier to pathogen growth once infection has occurred, and in some cases, reducing the severity of the disease. However, this mechanism of disease resistance has not been investigated in alfalfa. With the availability of alfalfa cultivars with the HarvXtra trait, experiments were conducted to determine if reduced lignin content would affect foliar disease resistance. Four Roundup Ready alfalfa cultivars, 54R02, DKA43-22RR, WL 355.RR, and the reduced lignin cultivar 54HVX41, were planted in three locations in Minnesota (Becker, Rosemount, and St. Paul). They were harvested at four maturity stages (early bud, bud, early flower, and flower). There were two harvests in which all four stages were present. At each harvest, 10 randomly selected stems were removed from each plot and scored for percent defoliation as a measure of disease severity. The occurrence of each disease was also rated over the season. The occurrence and severity of foliar diseases varied over time and across locations. Spring black stem and leaf spot (SBSLS) was observed throughout the season. It was the most damaging disease overall causing significant leaf loss and stem breakage. Leptosphaerulina leaf spot (LLS) and common leaf spot (CLS) were also seen through the season and increased in severity later in the summer. Summer black stem and leaf spot was most prevalent late in summer, particularly at the Rosemount location. When the data were analyzed across locations, there was a highly significant location by maturity by harvest interaction (P<0.0001). Up to 64% defoliation occurred if harvest was delayed until the flowering stage. When analyzed across all of the locations, there was a significant (P=0.032) location by maturity by cultivar interaction. However, For most of the maturity stages and at most locations, there were no significant differences among cultivars for percent defoliation. These results indicate that the HarvXtra trait does not affect foliar disease resistance.