Deep Purple Plum as a Rootstock for Nonpareil
John Edstrom, UCCE Farm Advisor
Stan Cutter, Nickels Soils Lab
Currently our most desirable almond variety, Nonpareil, can not be grown successfully
on any available plum type rootstock. Plum rootstock such as Marianna 2624 are known for
tolerating the soil disease oak root fungus, Armillaria mellea, and can often
withstand poorly drained and heavy textured soil conditions. Root lesion nematodes can
also be a serious problem to almonds especially in replant situations. Methyl bromide soil
fumigant is the most common and effective treatment for nematodes, however, its continuous
registration is in doubt.
The USDA Agricultural Research Service has identified a plum type
rootstock, Deep Purple (Prunus besseyi x p.salicina) which has shown potential as a
compatible rootstock for Nonpareil.
Deep purple has shown resistance to root knot and root lesion nematodes
in USDA Field trials in Fresno. The tolerance of this rootstock to Oak Root Fungus is,
however, unknown.
The objective of this trial is to evaluate the compatibility and field
performance of Nonpareil on Deep Purple rootstock as compared to Mission on M2624.
Trees were planted as rootstocks out of cold storage on April 22,1998,
and budded to scion varieties in May?. The following combinations were established in 4
replicates of 3 trees each: Nonpareil/Deep Purple, Nonpareil/M2624, Mission/Deep Purple,
Mission/M2624.
PROGRESS
The condition of much of the Deep Purple (DP) material was poor (small
trees, broken roots) compared to the M2624 material so DP began this test at somewhat of a
disadvantage. Significant loss of trees occurred in mid summer; 4 trees of 12 Nonpareil/DP
died and 3 of 12 Mission/DP died. The buds failed to take on 3 Nonpareil/M2624 and on 1
Mission/DP. Seasonal growth for the remaining trees would be considered fair.
