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 downy mildew (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, Guatemalan Green Ayote 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, had shown promise for DM resistance in our small plot trials (prior to this project). We have also gotten feedback from many farmers who have noticed its DM resistance and fruit quality. However, we felt more information was 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.

We also started this project with several seedstocks developed by crossing South Anna to other varieties (Atlas, JWS 6823, Guatemalan Green Ayote, and Chinese Tropical Pumpkin). One of our goals was to evaluate these populations and to begin selecting from them for  traits such as richer flavor, higher DM resistance, storage quality, higher fruit set, shorter vine length, larger fruit size (for processing), smaller fruit size (for market) . Part of the impetus for these crosses came from feedback from Clifton Seeds’ large scale 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 Community Farm has been trialing moschata squashes for several years. This project included evaluation and selection of the population they created by crossing Waltham and San Jose Mountain Club.

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 project had four elements:

1)2020 breeding trials at Twin Oaks Seed Farm and Care of the Earth Farm. This entailed evaluating separately trained plants as individuals. 194 plants were evaluated at Twin Oaks Seed Farm - populations included South Anna; Guatemalan Green Ayote (which likely has some Chinese Tropical Pumpkin mixed in); and crosses between South Anna and Atlas, Chinese Tropical Pumpkin, Guatemalan Green Ayote, and JWS 6823. The breeding trial of 125 plants at Care of the Earth Farm focused on a population derived from crossing Waltham and San Jose Mountain Club. We looked at yield per plant, eating quality, and keeping quality. The goal here was to advance breeding work by identifying and saving seed from standout plants; as well as to compare different populations to each other.

2)On-farm large block trials: We compared South Anna with Atlas F1, Quantum F1, Metro F1, Avalon F1 in blocks of approximately 3200 square feet. Large block trials took place at four organic farms in Virginia, North Carolina, and South Carolina: Wild Hope Farm,  Lomax Farm, Living Web Farm, and Twin Oaks Seed Farm. The goal was to get information from several farms about how South Anna compares to other varieties at field production scale. We looked at yield, eating quality and keeping quality.

3)The third element of the project was a screening of breeding lines and potential parents in smaller blocks that took place at both Care of the Earth Community Farm and Twin Oaks Seed Farm, with twelve 20-plant plots at Twin Oaks Seed Farm, and nine plots at Care of the Earth Community Farm. We looked at yield and eating quality.

4)2021 trials at Twin Oaks Seed Farm. In 2021 we compared small blocks of several 2020 selections and some new crosses. We also grew individually-trained plants derived from some 2020 selecions. The 2021 trials provided useful follow-up information to what we learned in 2020, and enabled us to make more progress with our selections.