2020 Apple Maturity Assessments: Week 8 Brak Fuji, BC2 Fuji, and HB-1

We additionally evaluated the cultivar HB-1 (Honeycrisp x Cripps Pink) grafted on M9 (without ReTain application), at Smithsburg, MD.

In general, fruits formed on all three cultivars are ready to be harvested for storage. Soluble solids contents are ~17%, with skin red coloration >60%, firmness values are in the range of 17-18lbs, starch index values between 4-5.5. We observed differences among the cultivars in their DA index values, which were significantly lower for HB-1 (0.4), and in the presence of the physiological disorder of watercore, which was present in both Fuji strains, but was not observed in HB-1 fruits. The information is summarized in Table 1.

Brak Fuji and BC2 Fuji Results

Color

Surface color: Brak Fuji fruits presented an average of 60% of red skin coloration, while BC2 Fuji displayed values around 75%. Both cultivars received a ReTain application, thus these differences can be due to different orchard sites where they are located. Brak Fuji showed a more intense red coloration than BC2 Fuji.

Background color (DA index): For both Fuji strains, DA index values ranged between 0.8 and 0.9, with readings <0.8 recommended for harvesting fruits for long-term storage.

Fruit firmness

Both Fuji strains displayed a decrease in their firmness values, which are ranging between 17~18 lbs (with ReTain application). Firmness was measured with a penetrometer with a 7/16-inch diameter plunger.

Starch content

Both strains are displaying a similar rate of starch breakdown, as both presented starch index values around 5.5. The common starch index rating system (Cornell chart) on a scale from 1 to 8, where 1 is full starch (all blue-black) and 8 is starch-free (no stain), was used. In general, on a 1 to 8 scale, values ranging from 4-6 are recommended for harvesting apples for long-term storage, while 6-7 for fresh market.

Soluble solids contents (SSC)

SSC values were around 16-17%, contributing to the popularity of Fuji as a sweet apple. As previously mentioned, the presence of watercore was detected in both strains, with a higher incidence in BC2 Fuji.

Acidity

Malic acid values did not decrease much in any of the two assessed Fuji strains and were maintained around 0.5% on average for all the evaluated fruits.

HB-1 Results

Color

Surface color: HB-1 fruits presented an average of 77% of red skin coloration, increasing its percentage from the past assessment as well as the minimum 60% required for harvest.

Background color (DA index): DA index values were ~0.4, significantly lower than the other assessed cultivars this week. Readings <0.8 are recommended for harvesting fruits for long-term storage.

Fruit firmness

HB-1 fruits displayed flesh firmness values ~18.5 lbs, with a targeted firmness for harvest of ~18lbs. Firmness was measured with a penetrometer with a 7/16-inch diameter plunger.

Starch content

The common starch index rating system (Cornell chart) on a scale from 1 to 8, where 1 is full starch (all blue-black) and 8 is starch-free (no stain), was used to evaluate the fruits. HB-1 fruits displayed a starch index value of 4.0, which falls into the range for commercial harvest for long-term storage (4-6).

Soluble solids contents (SSC)

SSC values were around 16-17%. We did not observe the presence of watercore in these HB-1 fruits, as we did for both Fuji strains and for Evercrisp fruits last week.

Acidity

Malic acid values decreased to 0.5% on average for all the evaluated fruits, as compared to our previous assessment.

Table 1. Summary table of maturity assessments for Brak Fuji, BC2 Fuji and HB-1. Values in parentheses indicate the results from week seven monitoring for Brak Fuji and from ~2 weeks ago for BC2 Fuji and HB-1. For fruit labeled with *, a ReTain application at the full rate was done on 10/1.