Evaluation of New Hybrid Cranberry Cultivars with Improved Fruit Quality, Yield and Disease Resistance

1. Establishment of cultivar trial

The project will be carried out on a ≈0.9-acre commercial cranberry bog at Mann Farms in East Wareham, MA (Latitude: 41.7748115; Longitude -70.6208475). The bog will be renovated in the winter of 2020/21 by applying 10 inches of sand to the existing planting. Drainage tiles and sprinkler irrigation system will be installed during bog renovation. The twelve hybrid cranberry cultivars to be evaluated are listed in Table 2.   

Table 2: List of cultivars to be evaluated in the project.

*There cultivars are not registered trademarks

-This list is not final and is subject to change pending additional consultations with cranberry growers and industry stakeholders over the summer.

-Efforts are being made to obtain more disease-resistant cultivars which are in final stages before commercial release at Philip E. Marucci Center for Blueberry and Cranberry Research and Extension in New Jersey.

Two cultivars, 'Stevens' and 'Mullica Queen®' will be used as the standard controls. 'Stevens' is the most widely grown cultivar in MA (Table 1) and 'Mullica Queen®' is a newer cultivar from New Jersey that does well in MA with the highest yields (Table 1). The experimental design will be a randomized complete block design with four plot replicates for each cultivar. Each plot replicate will be ≈ 40 feet long, and 15 feet wide with 2 feet buffer rows left in between. Cranberry vines will be sourced in December 2020 from the different breeding programs. The vines will be stored in a cooler at the UMass Cranberry Station and propagated as cuttings in a greenhouse at the UMass Cranberry Station. Standard commercial greenhouse guidelines will be followed during propagation. The rooted cuttings will be planted on the bog starting May 2021. After planting, standard cultural practices will be followed for fertilization, weed management, and irrigation.

2. Data collection:

Year 1: In Year 1, data collection aims to classify the ease of establishment of each hybrid cultivar and susceptibility to diseases. Data on light interception will be collected using a ceptometer to measure how easily the new cultivars grow under MA growing conditions. Disease resistance will be scored visually by looking at the severity of any symptoms that may appear. Samples will also be collected for pathogen identification in the lab using plating methods.

Year 2:  In Year 2, the bog will be flooded in spring to kill off all the flowers. This will stop fruit formation, and all the resources in the vines can be devoted to vegetative growth. By doing so, the new cultivars are expected to be fully established by the end of Year 2. Data collection in Year 2 will be similar to Year 1, focusing on the ease of establishment of each cultivar and susceptibility to diseases.

Year 3: Intensive data collection will start in Year 3. This will be the first year of production. During the spring, data will be collected on bloom phenology by counting the number of flowers on the fruiting uprights. Ten fruiting uprights will be tagged in each plot replicate for all the cultivars. The total number of flowers will be assessed as well as the length of the flowering period. The ratio of flowering to vegetative growth will also be determined by collecting biomass samples using a 6-inch ring in each plot replicate for all the cultivars, separating the uprights into different classes, and then counting them. Starting eight weeks before commercial harvest (≈ mid-August), fruit samples will be collected for maturity indexing. The samples will be collected using a square foot quadrant in each plot replicate. The sample from each plot replicate will be weighed to estimate yield. A sub-sample of 25 fruit will be collected to measure fruit length, fruit diameter and fruit firmness using a FirmTech Fruit Firmness Tester®. The rest of the sample will be divided into two. Half the sample will be tested for fruit color development using the standard total anthocyanin test. The other half will be used to measure total soluble solids and titratable acidity. At commercial harvest, two square foot quadrants will be collected from each plot replicate for a more accurate estimate of yield potential. The samples collected at commercial harvest will also be assessed for fruit rot incidence in addition to the other tests described above.

Year 4 - Year 7: Although these years fall outside the timeline on this project, data collection will continue until Year 7. Full production is expected to be in Year 5, and yield data collected over several years may indicate trends like the susceptibly of the new cultivars to alternate bearing. Therefore, it is essential that data collection continues past the duration of project funding.

Data collected will be analyzed using one way ANOVA for significant differences between cultivars.

Progress ending 12/31/2020:

1. Material Transfer Agreements (MTA)
   1. On the 14^th of September 2020, we signed a standard MTA for the transfer of biological materials with the Wisconsin Alumni Research Foundation for the transfer of Ruby Star®, Sundance® and Hyred®.
   2. On the 21^st of September 2020, we signed a standard MTA for the transfer of biological materials with Valley Corporation for the transfer of Crimson King, Valley King, Pilgrim King, Midnight 8, and Granite Red.
   3. As of December 2020, the MTA with Rutgers University was still outstanding. An issue arose pertaining to the sale of berries after samples have been collected. The problem was resolved, and the MTA is expected to be signed during the next reporting period.
2. Propagation material
   1. In December 2020, we received the propagation material from Cranberry Creek Cranberries (representing the Wisconsin Alumni Research Foundation) and Valley Corporation. Valley Corporation replaced Valley King variety with Badger. They felt the latter was more suited to MA growing conditions. 
   2. The propagation material was stored in a walk-in cold room at 45°F and 100% relative humidity.

Progress ending 12/31/2021.

Propagation of the rooted cuttings began in early March in the greenhouse and continued until April. At the same time in March, the renovation of Section 1 of State Bog (≈0.75 acres)  at the UMass Cranberry Station was initiated. Initially, the project was going to be conducted at a grower collaborators' site. Unfortunately, because of some of the conditions that were imposed by one of the breeding programs, the location had to be shifted to the UMass Cranberry Station. The grower collaborator is still involved in the project, with regular meetings being held to discuss the progress of the project. The grower collaborator has also visited the new planting for an on-site meeting. The renovation included stripping off the top 10 inches of the bog and replacing it with new sand. A new irrigation and drainage system was also installed. The planting of the new cultivars started at the beginning of June and was finished by the end of June. The new cultivars were irrigated twice daily for 30 mins each, following guidelines for new cranberry plantings. The rooted plugs were planted at the industry standard 1-foot spacing. At planting, 50 lbs/A nitrogen and 100 lbs/A phosphorous were applied to the new planting following recommendations for new planting. After the roots were established, 10lbs nitrogen was applied every two weeks until mid-August. The new vines were successfully established with high colonization rates at the end of the growing season. At the end of the growing season in September, aerial imaging was done using a drone to quantify the establishment of the vines. The data is still being analyzed.

Progress ending 12/13/2022

To enable the evaluation of varietal performance under Massachusetts conditions, the following activities were carried out during the current reporting period (1) data collection with drones, (2) collecting vegetative samples for nutrient assessment, (3) preliminary fruit quality assessment (color and rot) (4) assessment of weed infestations (5) assessment of insect damage.

Data was collected using drones with red-green-blue (RGB) and multispectral cameras. The data images collected using drones were stitched together, and maps were created to evaluate the (1) establishment rate of the new cultivars and (2) health of the new cultivars using vegetation indices such as normalized difference vegetation index (NDVI). They were clear differences in establishment rates based on drone data (Figure 1).  The top performing cultivars in terms of canopy establishment were RU 4, VC 1, and VC 3.  The same trend applied to canopy health with clear differences observed between cultivars(Figure 2).

Fertilizer applications at the study site were managed as per current UMCS recommendations for new plantings. At the end of the growing season, samples were collected and sent for nutrient assessment to determine the response of the different cultivars to fertilizer application as per current guidelines. The results from plant tissue analysis are still being analyzed and will be used to adjust fertilizer recommendations for the coming growing season. 

Fruit samples were collected at 2-week intervals for assessment of fruit color (Figure 3). The samples were stored in the freezer and will be used to assess fruit color using the total anthocyanin method (we had no access to the labs because of building renovations).

Weed infestations at the study site were managed as per current UMCS recommendations for new plantings of cranberry vines. Growers strive to maximize cranberry vines colonization in Years 1-3 by minimizing weed infestations. Weeds in new cranberry plantings are managed with the use of pre-emergence and postemergence herbicides and hand weeding. The following herbicides were applied to the study site in 2022: Devrinol 2XT (napropamide) at 9 qt/A on 20 May and 29 June; Callisto (mesotrione) at 8 oz/A on 6 June, and Intensity One (clethodim) at 16 oz/A on 6 June and 8 July. Periodic hand-weeding was performed as needed throughout the season. The most common weeds in the study site were soft rush (Juncus effusus), haircap moss (Polytrichum spp.), crabgrass (Digitaria sanguinalis), and orange grass (Hypericum gentianoides). No insect damage was observed during the reporting period on the test plots

As of the 2022 growing season, as the canopy/planting is still establishing, we did not specifically observe any particular cultivar highly resistant or susceptible to diseases. In 2023, we will monitor closely for fruit rot and other diseases (Phytophthora root rot, Upright dieback) of commercial importance in Massachusetts.