Improved Productivity of Chambourcin Grape Grafted to Seven Rootstocks

The French hybrid grape cultivar 'Chambourcin' (Joannés-Seyve 26.205) was planted in 2004 at Mountain Grove, Mo., on seven rootstocks.  These were 3309C, 101-14, 5BB, SO4, 110R, 1103P, and Freedom.  Own-rooted 'Chambourcin' was also grown.  The planting site attributes are latitude 37° 9' N, longitude 92° 16' W, elevation 442 m, USDA plant hardiness zone 6a, and a Viraton silt loam soil with 2 to 5% slope.  The latter is characterized as acidic, moderately well-drained, and slowly permeable with chert and fragipan in the subsoil.  This soil restricts root growth, is drought prone, and can reduce vine vigor.  Rootstocks were tested in a replicated trial during the years 2009 to 2013 to improve scion productivity.  'Chambourcin' on its own roots had significantly lower yield per vine than those grafted to 3309C, 5BB, and 1103P.  The remaining rootstocks were intermediate, not significantly different from own-rooted, but always higher in yield per vine.  Average cluster and berry weights showed significant differences among rootstocks in some years.  Own-rooted was always the lowest.  Soluble solids showed a negative relationship to yield per vine in some years.  Own-rooted was always the highest.  Juice pH and titratable acidity showed a significant difference in only one year, 2010 for pH.  Pruning weight per vine showed a positive relationship to yield per vine in most years.  Own-rooted was always the lowest.  The vines grafted to 3309C and 1103P were significantly higher in pruning weight per vine with the remaining intermediate.  It is clear that 'Chambourcin', a cultivar prone to low vigor on a restrictive soil, can improve in productivity when grafted to rootstock.