Breeding and Evaluation of Butternut Squash Varieties for Southeast Organic Farms

View the project final report

Commodities

• Vegetables: cucurbits

Practices

• Crop Production: plant breeding and genetics, seed saving

Using selective breeding to address disease problems can be an extremely effective solution that causes none of the environmental and health dangers posed by chemical fungicides (which are unfortunately the current go-to for DM). Moreover, eliminating or reducing need for chemical sprays saves farmers money and improves feasibility of Southeast production. DM in cucumbers was effectively controlled for many years by the use of resistant varieties. We aim to do the same with butternut squash, and whats more we aim to develop and utilize diverse sources of DM resistance so that the resistance will be more durable and resilient in the face of potential changes to the pathogen in the future. This includes using Seminole Pumpkin, San Jose Mountain Club Squash and Chinese Tropical Pumpkin as DM resistance sources.

South Anna Butternut, a variety Common Wealth Seed Growers developed from a cross between Seminole Pumpkin and Waltham Butternut, has shown promise for DM resistance in our small plot trials (see previous section). We have also gotten feedback from many farmers who have noticed its DM resistance and fruit quality. However, more information is needed to assess its potential in the region in comparison to other varieties in terms of not only DM resistance, but productivity and fruit quality.

CWSG has several new F2 seedstocks developed by crossing South Anna to other varieties (Atlas, JWS 6823, Chinese Tropical Pumpkin). We will begin selecting from these populations to develop new DMR varieties with traits such as shorter vine length, larger fruit size (for processing), smaller fruit size (for market), richer flavor, higher DM resistance, and higher fruit set. Part of the impetus for these crosses came from feedback from Clifton Seeds’ 2018 test of South Anna. They said it stood out for DM resistance but needed higher fruit set and larger fruit (many of their seed customers grow for processing).

In addition, Care of the Earth Farm has been trialing moschata squashes for several years. Their cross of Waltham and San Jose Mountain Club has shown promise (see below), but more work is needed for their goal of creating a new DMR butternut variety.

All our work with squash at Twin Oaks Seed Farm and Care of the Earth Farm is conducted on certified organic land, with minimal pest and disease control inputs. As a result our selections are well suited to survive the pest and disease challenges that Southeast organic growers face. This also stands to benefit conventional growers by reducing need for chemical inputs.

Very early planting is one way organic growers and some conventional growers have handled DM. Limitations are that summer-harvested butternut crops don't keep long into the fall, and that in some years severe DM comes early. South Anna, and other varieties we are developing, are intended to be grown in high DM conditions for fall harvest, allowing fruits to keep longer into the fall and winter. Note that assessing the performance of very early planted, summer-harvested butternuts is beyond the scope of this project.

The current project has three elements:

1)On-farm block trials: We will compare South Anna with two of the following popular butternut varieties (TBD): Quantum, Avalon, Atlas, Waltham. Trials will take place at five organic farms in Virginia, North Carolina, and South Carolina: Wild Hope Farm, Hickory Meadows Organics, Lomax Farm, Living Web Farm, and Twin Oaks Seed Farm. Each farm will grow two plots of South Anna and one plot of each of two other varieties (following what is known as an augmented trial design). Plantings at the different farms will also be looked at as replications when analyzing the data. The multi-row plots will be relatively large (4300 square feet) to more accurately represent normal production conditions. Trials will be planted somewhat late, approximately 140 days before expected first frost, to ensure presence of downy mildew. Data collected in the field will include downy mildew foliage ratings (along with documentation of any other diseases that may appear), and yield (measured by volume). Fruit quality will be evaluated with brix tests, dry matter tests, and keeping quality tests. A two-bushel representative sample from each plot will be collected at each trial site, and picked up for evaluation at Common Wealth Seed Growers in Virginia. Many of the growers involved attend the Carolina Farm Stewardship fall conference and we expect to be able to pick up much of the squash there.

2)Breeding trials at Twin Oaks Seed Farm and Care of the Earth Farm. Breeding trials at Twin Oaks Seed Farm will contain 200 separately-trained plants of several 2019 South Anna selections, and F2 plants from crosses between South Anna and Atlas, JWS 6823, and Chinese Tropical Pumpkin. Breeding trials at Care of the Earth Farm will contain 100 F3 plants derived from a cross between San Jose Mountain Club Squash and Waltham Butternut. We will measure DM resistance and yield for these plants, and approximately the best 30% will also be evaluated for fruit quality (brix, dry matter, shape, size, color, taste tests). Breeding trials will either be isolated to avoid crossing with other varieties, or plants will be self-pollinated.

3)The third element of the project is a screening of breeding lines and potential parents – to take place at both Care of the Earth Farm and Twin Oaks Seed Farm. Twelve 20-plant plots will be grown at each farm and assessed for DM resistance, yield, and fruit quality (brix, dry matter, shape, size, color, taste tests). At least half the screening entries will be grown at both farms. Entries could include: F1 crosses between South Anna and other varieties; different 2019 selections of South Anna; different selections from San Jose Mountain Club x Waltham; and varieties such as Quantam, Atlas, Avalon, Seminole Pumpkin, Tahitian Butternut, and Waltham.

Jared Zystro of Organic Seed Alliance will serve as an advisor to the project, providing help and advice in trials layout and in analyzing and presenting the data.