2020 Apple Maturity Assessments: Week 7 Brak Fuji, Evercrisp, and HB-1
Watercore is a physiological disorder caused by the accumulation of sorbitol-rich liquid—the primary transport of carbohydrate in apple, in the intercellular spaces of the apple tissue. Photo courtesy of the Farcuh Lab.
Additionally, we evaluated the cultivar HB-1 (Honeycrisp x Cripps Pink) grafted on M9 (without ReTain application), at Smithsburg, MD.
In general, for all of these late-season cultivars, we have observed high soluble solids contents (>16 %) accompanied by a high percentage of red skin coloration (> 50%, enhanced by the cooler temperatures that we have been experiencing). It is worth mentioning that in Brak Fuji and Evercrisp we have observed the presence of the physiological disorder of watercore starting to develop. Fruits from all assessed cultivars are firm (18 to 23 lbs) and displaying starch pattern indices ranging between 3 to 4.5. Based on these results, the harvest of most of these cultivars should be anticipated for the last week of October. The information is summarized in Table 1.
Brak Fuji Results
Color
Surface color: Brak Fuji fruits presented an average of 55% of red skin coloration, although it displayed the lowest skin red color percentage when compared to the other two assessed cultivars. This could be influenced by the ReTain application that this cultivar received as well as by genetic factors.
Background color (DA index): DA index values ranged between 1.0 and 1.1, while readings <0.8 are recommended for harvesting fruits for long-term storage.
Fruit firmness
Fruits are displaying high firmness values (~18 lbs), which can be related to the ReTain application that they received. 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. Brak Fuji fruits this week displayed a starch index value of 4.5. 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 Brak Fuji as a sweet apple. It is worth indicating that we observed the presence of watercore starting to develop in this cultivar. Watercore is a physiological disorder caused by the accumulation of sorbitol-rich liquid (primary transport carbohydrate of apple) in the intercellular spaces of the apple tissue. The accumulation of sorbitol-rich liquid attracts water from the cells, causing this translucent aspect. Watercore only develops on the tree, but in case of mild/moderate symptoms, these may disappear during storage.
Acidity
Malic acid values were measured at 0.5% on average for all the evaluated fruits, and we expect this value to decrease, as a decrease in acidity contents is an indicator of advancing maturity.
Evercrisp Results
Color
Surface color: Evercrisp fruits presented an average of 85% red skin coloration, which could have been enhanced by the cooler temperatures that we have been experiencing.
Background color (DA index): DA index values are ~0.8, which is the recommended limit for starting to harvest fruits that will be destined for long-term storage.
Fruit firmness
Evercrisp fruits are displaying the highest firmness values (~23 lbs) when compared with all the other assessed cultivars, which is characteristic of this cultivar. 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. Evercrisp fruits this week displayed a starch index value of 4.0. 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 18.5% for Evercrisp, displaying the highest SSC among all the assayed cultivars this week. We also observed the presence of watercore starting to develop in this cultivar.
Acidity
Evercrisp apples also displayed the highest malic acid values (0.7%) as compared with the other two evaluated cultivars for this week.
HB-1 Results
Color
Surface color: HB-1 fruits presented an average of 70% red skin coloration, and is targeted to be harvested with at least 60%.
Background color (DA index): DA index values ranged ~0.5 which were the lowest among all the 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 ~20 lbs, and the targeted firmness for harvest is ~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 this week displayed a starch index value of 3.0. 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%. We did not observe the presence of watercore in these HB-1 fruits.
Acidity
Malic acid values were measured at 0.6% on average for all the evaluated fruits, and we expect this value to decrease, as a decrease in acidity contents is an indicator of advancing maturity.
Table 1. Summary table of maturity assessments for Brak Fuji, Evercrisp, and HB-1. For fruit labeled with *, a ReTain application at the full rate was done on 10/1.
