Commercial Hard Squash Cultivars Exhibit Differences in Susceptibility to Phytophthora Crown Rot

Squash, including Cucurbita pepo, Cucurbita moschata, and Cucurbita maxima, are widely grown for their fruits and seeds, which provide nutritional and ornamental value in many cultures (Loy 2004; Paris 2018; Whitaker and Bohn 1950). Michigan growers planted 3,359 ha of squash in 2021, representing nearly 20% of the total United States’ acreage (USDA 2022). In 2020, Michigan growers produced nearly 27,200 metric tons of processing squash (USDA 2022) for use as pie filling, canned food, frozen food, and baby food. Michigan processing squash growers rank fourth in the United States in total production while facing narrow profit margins and stringent national canning standards (Lennartson 1956; USDA 2022). The primary varietal groups of hard squash grown in Michigan include Acorn (C. pepo), Butternut-Bell (C. moschata), and Delicious (C. maxima) (M. Hausbeck, personal communication).

The Cucurbitaceae family is a diverse plant group (Paris 2018) with many species severely affected by the soilborne pathogen Phytophthora capsici (Café-Filho et al. 1995; McGrath 2017). Fruit and/or crown rot of squash, cucumber, melon, and pumpkin caused by P. capsici can result in complete crop loss; both fruit and crown rot must be managed (Babadoost and Zitter 2009; Hausbeck and Lamour 2004). In cucurbits, P. capsici may cause damping-off of seedlings, vine and foliar blight, and crown rot of mature plants. Crown rot symptoms of mature plants begin with wilting, followed by water soaking and, finally, permanent wilt and the death of the plant (Babadoost 2004; Hausbeck and Lamour 2004). Fruit rot often occurs when fruits are in contact with P. capsici-infested soil (McGrath 2017). Infested soil or pathogen propagules may be splash-dispersed onto the plant crown or fruit during rain or overhead irrigation (Hausbeck and Quesada-Ocampo 2017). Fruit rot symptoms can also occur postharvest (McGrath 2017). Initial symptoms include water-soaked lesions that become sunken and expand, resulting in fruit collapse (McGrath 2017). Sporangia produced on the fruit surface have a powdered sugar-like appearance (Hausbeck and Lamour 2004). Fruits that have long maturation periods, such as winter squash and pumpkins, and remain in direct contact with infested soil for long periods have an increased likelihood of fruit rot (Granke et al. 2012).

Crop rotation and the destruction of infected plant debris are not effective as standalone management practices to limit Phytophthora blight because the pathogen's oospores may survive in the absence of a host for extended periods (Lamour and Hausbeck 2003). A Phytophthora blight epidemic on squash following a 5-year rotation with non-host crops indicated that standard rotations of 3 to 4 years are insufficient (Lamour and Hausbeck 2003). Crop rotations longer than 5 years may not be feasible in Michigan due to the limited availability of non-infested fields suitable for vegetable production (Hausbeck and Lamour 2004). Furthermore, some rotational and alternative crops in the squash-producing areas of Michigan, including snap bean (Phaseolus vulgaris) and Fraser fir (Abies fraseri), can be hosts of P. capsici (Gevens et al. 2008; Quesada-Ocampo et al. 2009).

Drip irrigation, raised plant beds, and black plastic were proposed by Ristaino and Johnston (1999) as important cultural methods to lessen the risk of Phytophthora blight on peppers. Phytophthora blight incidence on pepper was 18% in flat beds and 5% in raised beds (Hwang and Kim 1995). Similarly, plant death of zucchini in a field naturally infested with P. capsici was greater in flat beds versus raised beds (Hausbeck and Lamour 2004). Covering raised beds with plastic mulch may further reduce the risk of Phytophthora blight by minimizing splash dispersal of P. capsici-infested soil to susceptible plant tissues (Ristaino et al. 1997). Use of raised beds with plastic mulch is conducive to application of fungicides through drip irrigation and reduces soil saturation in the root zone (Hausbeck and Lamour 2004; Springer and Johnston 1982). Currently, these strategies are widely used to produce fresh market vegetables, including squash (Meyer and Hausbeck 2012). However, growers that produce hard squash for processing do not employ these strategies due to low profit margins and the use of mechanical harvesters in some systems (Hausbeck and Quesada-Ocampo 2017).

Early and frequent fungicide applications are required for maximum disease control but increase production costs. The ability of the pathogen to reproduce sexually increases the likelihood of the pathogen developing resistance to fungicides, including mefenoxam (Hausbeck and Lamour 2004) and cyazofamid (Jackson et al. 2012). In Michigan, 45% of the 498 P. capsici isolates obtained from diseased vegetables growing on select farms were resistant to mefenoxam (Lamour and Hausbeck 2000).

Host resistance to P. capsici among commercial and experimental pepper cultivars has been identified (Dunn et al. 2014; Krasnow et al. 2017; Parada-Rojas and Quesada-Ocampo 2019). In tomato, Phytophthora crown and root rot resistance was identified in an accession of Solanum habrochaites with moderate levels of resistance (Quesada-Ocampo and Hausbeck 2010). Age-related resistance, also known as ontogenic resistance, to Phytophthora fruit rot has been identified in cucurbits, but its onset differs by crop (Ando et al. 2009). The fruits of acorn and butternut squash, and some cucumber and pumpkin varieties, become less susceptible to P. capsici as they mature. In contrast, summer squash, zucchini, and melon fruits remain susceptible (Ando et al. 2009). The fruits of C. moschata cultivars develop age-related resistance 14 to 21 days post-pollination (dpp) (Alzohairy et al. 2020; Meyer and Hausbeck 2013).

The varietal group of Delicious hard squash, including ‘Golden Delicious’, ‘NK 530’, ‘NK 580’, and ‘Green Delicious’, is characterized as having a red-orange and tender rind (with the exception of Green Delicious, which has a green rind), which is desired for processing squash, and thick orange-yellow flesh maturing at approximately 115 days post planting (Oregon State University 2010). Among the Delicious cultivars, NK 580 has been preferred for processing contracts in the northern growing region of Michigan due to the color, consistency, texture, and sugar content of the fruit (Loy 2004; M. Hausbeck, personal communication). Following an outbreak of Phytophthora fruit rot (>90% incidence) in a 32-ha field of NK 580 in Mason County, MI (Meyer and Hausbeck 2013), growers became concerned that continuing to grow NK 580 was not sustainable due to the susceptibility of its fruit. Similarly, Meyer and Hausbeck (2013) determined that Golden Delicious was susceptible to fruit rot even at full maturity; about 80% of Golden Delicious fruits were susceptible at 21 dpp or later. In contrast, few (<15%) fruits of the C. moschata cultivar Dickinson Field became diseased at 21 dpp or later.

We sought to determine whether currently available commercial cultivars of winter squash differ in resistance to Phytophthora capsici, specifically resistance of the crown, and to assess select fruit characteristics relevant to processing. This information will assist Michigan growers in identifying possible alternatives to the highly susceptible NK 580 squash preferred by local processors.

Evaluation of Squash Cultivars for Resistance to Crown Rot

Four C. moschata cultivars and eight C. maxima cultivars were included in field experiments conducted during the summer of 2020 and 2021 at the Michigan State University (MSU) Southwest Research and Extension Center near Benton Harbor, MI, in a sandy soil previously planted to squash (Table 1). Prior to planting, glyphosate (Roundup PowerMax at 2.34 liters/ha, Monsanto Company, St. Louis, MO) was applied for weed control, and fertilizer (nitrogen 114 kg/ha, potassium 205 kg/ha, sulfur 28.4 kg/ha, and boron 2.3 kg/ha) was spread. Plants were grown at the MSU Plant Science Greenhouse in East Lansing, MI, and established from seeds (Table 1) planted into 72-cell trays containing soilless peat mixture (Suremix, Michigan Grower Products, Galesburg, MI). Prior to transplanting, 2-week-old seedlings were removed from the greenhouse and kept outside for 7 days to acclimate. Three-week-old squash seedlings were transplanted 0.45 m apart into 0.15-m raised plant beds covered with black polyethylene plastic (0.15 m high by 0.6 m wide) with rows spaced 7.9 m apart on 15 June 2020 and 10 June 2021. For plot irrigation, a single drip tape (2.47 LPM/30.5 m) was installed under the plastic mulch. Throughout the growing period, plants were fertilized weekly (28% nitrogen at 65 liters/ha) through drip irrigation, and weeds were controlled manually and mechanically. Treatments were arranged in a randomized complete block design with four replicates. A replicate consisted of a single 6.1-m row with a 1.3-m buffer between treatments within a row.

TABLE 1 Plant death and relative area under disease progress curve (rAUDPC) among squash cultivars when inoculated with Phytophthora capsici in 2020 and 2021

	Plant death (%)s		rAUDPCt
Cultivar	2020	2021	2020	2021	Mean across yearsu
Cucurbita moschata (Butternut)
Buckskinv	13.5 ew	1.9 b	2.2 d	0.2 c	1.2
Dickinsonx	13.5 e	1.9 b	6.0 cd	0.8 c	3.4
New England Cheddarx	9.6 e	0.0 b	3.2 d	0.2 c	1.7
Ultra Butternutx	3.8 e	0.0 b	1.9 d	0.0 c	0.9
Cucurbita maxima (Hubbard)
Golden Deliciousx	88.5 a–c	100.0 a	44.6 a	39.3 a	41.9
NK 580x	88.5 a–c	100.0 a	30.6 ab	39.3 a	35.0
Cucurbita maxima (Kabocha)
Autumn Cupx	63.5 b–d	92.3 a	20.2 bc	27.8 ab	24.0
Delicay	92.3 ab	100.0 a	41.6 a	36.4 a	39.0
Space Stationx	51.9 d	92.3 a	14.7 b–d	35.3 ab	25.0
Sunshinez	90.4 ab	100.0 a	41.6 a	38.7 a	40.1
Sweet Mamax	94.2 a	96.2 a	44.1 a	37.2 a	40.1
Thunderx	59.6 cd	76.9 a	22.4 b	20.3 b	22.3
P value	<0.0001	<0.0001	<0.0001

^s Final rating recorded 27 (2020) and 35 days (2021) postinoculation.

^t Calculated using three observations over 27 days in 2020 or five observations over 35 days in 2021.

^u Average calculated using the rAUDPC values from each cultivar across 2020 and 2021.

^v Stokes Seeds, Holland, MI.

^w Column means with a letter in common are not statistically different (Tukey's honestly significant difference; P = 0.05).

^x Rupp Seed, Wauseon, OH.

^y Harris Seeds, Rochester, NY.

^z Johnny's Selected Seeds, Winslow, ME.

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Plants were inoculated with P. capsici-infested millet seed (Pennisetum glaucum) (Quesada-Ocampo and Hausbeck 2010) at 50 (2020) and 33 days (2021) after transplanting. Strains 14118 (isolated from cucumber, A1 mating type, sensitive to mefenoxam) and SP98 (isolated from pumpkin, A2 mating type, sensitive to mefenoxam) were recovered from the Hausbeck lab culture collection at MSU. The long-term cultures were plated on BARP (25 ppm benomyl, 100 ppm ampicillin, 30 ppm rifampicin, and 100 ppm pentachloronitrobenzene) and posteriorly transferred to amended UCV8 (3 g of CaCO3, 15 g of agar, 160 ml of unfiltered V8 juice, and 840 ml of distilled water) (Quesada-Ocampo and Hausbeck 2010). The inoculum mixtures included 100 g of sterilized millet, 72 ml of distilled water, 0.08 g of asparagine, and seven 7-mm plugs of one of the P. capsici isolates. The pathogen (each isolate) was inoculated into and subsequently recovered from squash fruit to ensure pathogen virulence prior to infestation of the millet (Quesada-Ocampo and Hausbeck 2010). The infested millet seed was incubated at room temperature (20 to 22°C) under constant fluorescent lighting for 5 weeks. The two infested millet batches, each containing one of the two isolates, were mixed in a 1:1 ratio before inoculation (Krasnow and Hausbeck 2016). Squash plants in the field were inoculated by inserting 2 g of infested millet in a depression made in the soil 2 to 3 cm from the seedling crown and covered with soil.

Disease incidence (%) was assessed weekly by counting the number of plants dying of P. capsici symptoms. Following the final field disease evaluation, and to confirm Koch's postulates, each plot was divided into three pseudo plots containing four plants each, and one plant was removed from each pseudo plot using a small shovel. Selected samples were placed individually into a paper bag and stored in a cooler to be transported to the MSU laboratory. In some plots, plants were not available for sampling as they were significantly rotted and deteriorated. Symptomatic root tissue was surface disinfected with 10% sodium hypochlorite (NaOCl) solution (121 ml of household bleach solution containing 8.25% NaOCl) (Krasnow and Hausbeck 2016), cut into small pieces (100 × 15 mm), plated on BARP (25 ppm benomyl, 100 ppm ampicillin, 30 ppm rifampicin, and 100 ppm pentachloronitrobenzene), and posteriorly transferred to amended UCV8 (840 ml of distilled water, 163 ml of unclarified V8 juice, 3 g of CaCO₃, and 16 g of Bacto agar) plates. Plates were sealed with Parafilm (Amcor Limited and Bemis Company, Neenah, WI) for 5 days; then, the parafilm was removed from the plates, which were incubated under constant fluorescent light at room temperature (20 to 22°C) for 2 to 3 days to induce sporangial production. Morphological characteristics associated with P. capsici, including coenocytic hyphae and irregular, papillated sporangia on long pedicels, were confirmed via microscopy (Waterhouse 1970).

The relative area under the disease progress curve (rAUDPC) was calculated using the formula ((AUDPC)/N) as proposed by Fry (1978), where the standard area under disease progress curve (AUDPC) (Shaner and Finney 1977) was divided by the number of days (N) from inoculation date to the final rating date. These variables were calculated in Excel v. 2210 (Microsoft, Redmond, WA). All data were analyzed using a linear mixed model using PROC GLIMMIX in SAS 9.4 (SAS Institute Ins., Cary, NC).

For each year (2020 and 2021), disease incidence at the final rating date was analyzed independently (Table 1). Year (2020 and 2021), cultivar, and their interaction (year × cultivar) were considered fixed effects, whereas block nested in cultivar was considered a random effect. The standard error and degrees of freedom correction were predicted using the Kenward-Roger option. The normality assumption of each data set was investigated by observing studentized residuals plots, residuals versus predicted means plots, and a percentage of residual distribution histogram. The homogeneity assumption was checked using Levene's test (P < 0.05). Data were transformed using the square root of n and posteriorly back transformed using n². For disease incidence at the final rating date and rAUDPC, the post-hoc Tukey's honestly significant difference test was performed for pairwise and multiple comparisons (P < 0.05).

Crown rot symptoms were observed at 13 and 4 days postinoculation in 2020 and 2021, respectively. The number of diseased plants exhibiting crown rot symptoms including wilting, sunken dark lesions on the lower stem and crown, and girdling of the crown at the plant base were determined, and P. capsici was confirmed from the symptomatic plants collected after the last rating date. Each year, the C. moschata cultivars exhibited the lowest incidence of plant death (≤13.5%) compared to all other cultivars included in the study at 27 (2020) and 35 (2021) days postinoculation (Table 1). In contrast, the two Hubbard-type C. maxima cultivars exhibited high incidence of plant death (≥88.5%). The Kabocha-type C. maxima cultivars exhibited a range of susceptibility, with incidence of plant death ranging from 51.9 to 100% across both years. The Kabocha-type cultivars Sweet Mama, Sunshine, and Delica had a consistently high incidence of plant death each year (Table 1). In 2020, the Kabocha-type cultivar Thunder had a lower incidence of plant death (<60.0%) compared with the most susceptible Kabocha cultivars (Delica, Sunshine, and Sweet Mama); significant differences were not noted in 2021.

According to the rAUDPC data for incidence of plant death, cultivars (P < 0.0001) and years (P = 0.014) differed significantly, and the interaction was significant (P < 0.0001). In 2020, the C. moschata cultivars were less susceptible to crown rot than the C. maxima Hubbard-type cultivars and the C. maxima Kabocha cultivars Sweet Mama, Sunshine, Delica, and Thunder. In 2021, the C. moschata cultivars expressed lower rAUDPC values than all other cultivars evaluated. The Kabocha-type cultivar Thunder had a lower rAUDPC value (≤22.4) relative to the most susceptible Kabocha cultivars (Delica, Sunshine, and Sweet Mama) in both years.

Evaluation of Squash Cultivars for Fruit Quality

Healthy, mature fruits were sampled from field experiments conducted in 2019 and 2020. The 2019 study was planted on 18 June in a field with Capac loam soil previously planted to tomato at the MSU Plant Pathology Farm located in Lansing, MI. The 2020 study was planted on 15 June on a sandy soil previously planted to squash at the Southwest Research and Extension Center. Cultivars and crop management practices aligned with those previously described for the crown rot trial, but experiments were conducted separately; plants in the fruit quality experiment were not inoculated.

For each cultivar, two to four healthy fruits were collected at maturity from each of three field replicates. Fruits were weighed to calculate average fruit weight (kilograms per fruit), then sliced longitudinally (stem to calyx). Flesh (mesocarp) was separated from the rind, placenta, and seeds. Following dicing, representative slices from each fruit replicate were combined. A subsample of the diced flesh was juiced, followed by a determination of soluble solids as degrees Brix (°Brix) using a digital refractometer (PAL-1, Atago Co. Ltd., Tokyo, Japan) based on the mean of three replicate readings per sample. The remaining portion of diced flesh was weighed fresh, dried at 60°C to constant weight, and then weighed dry for determination of the percentage of dry matter (dry weight/fresh weight × 100). Data were analyzed by a mixed-model ANOVA using PROC GLIMMIX in SAS 9.4 (SAS Institute Ins.). Years were analyzed separately, with cultivar included as a fixed effect and replicate as a random effect in the model. Log transformation and unequal variance models were used when necessary to meet ANOVA assumptions of normality and equality of variances. Tukey's honestly significant difference test was used for cultivar pairwise comparisons (P < 0.05).

Cultivar suitability for Michigan processors and buyers of processed products depends on numerous characteristics, including yield, quality, and processing efficiency (Loy 2004). To provide a preliminary context for our evaluation of Phytophthora crown rot resistance in commercially available cultivars, we measured a subset of characteristics reflective of sugar content (soluble solids), consistency and viscosity (dry matter), and product yield and handling requirements (average fruit weight). Desirable ranges for these characteristics vary among processors and intended end uses, but soluble solid levels of 6.0 to 7.0 °Brix and dry matter of at least 9 to 11% are common targets for Hubbard cultivars grown for pie filling (Loy 2004).

Fruit characteristics were similar between the two Hubbard cultivars (Table 2). Both Hubbard cultivars accumulated greater than 6.0 °Brix in 2020 but less than 5.0 °Brix in 2019. Relative to the Hubbard cultivars, all Kabocha-type cultivars had higher soluble solids, ranging from 7.5 to 10.8 °Brix. Kabocha-type cultivars also exhibited greater dry matter and smaller average fruit weights than NK 580, with the exception of Sweet Mama, in which fruit weight was greater than the other Kabocha-type cultivars and statistically similar to NK 580 in one year. The C. moschata cultivars Buckskin, Dickinson, and New England Cheddar had the largest average fruit weights of all evaluated cultivars. Soluble solids and dry matter were similar to both Hubbard-type cultivars in 2019 but lower than Golden Delicious in 2020, with soluble solids never exceeding 5.3 °Brix. By comparison, the C. moschata cultivar Ultra Butternut had similar or greater °Brix (6.6 and 7.2 in 2019 and 2020, respectively), dry matter, and fruit weight compared with the industry-preferred Hubbard cultivars in both years.

TABLE 2 Selected quality characteristics of healthy, mature fruit sampled from squash cultivars grown in 2019 and 2020

	Soluble solids (°Brix)u		Dry matter (%)u		Average fruit weight(kg/fruit)
Cultivar	2019	2020	2019	2020	2019	2020
Cucurbita moschata (Butternut)
Buckskinv	4.0 aw	5.2 a	5.0 ab	6.4 ab	4.9 d	6.8 f
Dickinsonx	4.9 ab	4.9 a	5.8 a	5.9 a	6.3 d	6.9 f
New England Cheddarx	5.3 a–c	4.7 a	5.5 a	5.6 a	5.8 d	6.3 f
Ultra Butternutx	6.6 b–d	7.2 b	8.4 bc	10.2 c	2.6 c	3.3 c–e
Cucurbita maxima (Hubbard)
Golden Deliciousx	4.9 ab	7.3 b	6.6 a–c	11.2 c	1.8 bc	3.4 e
NK 580x	4.3 ab	6.3 ab	5.2 a	8.9 bc	2.1 c	2.5 de
Cucurbita maxima (Kabocha)
Autumn Cupx	8.6 d	9.5 c	13.2 d	17.1 d	1.0 ab	1.1 a
Delicay	8.8 d	10.6 c	12.2 d	21.9 de	0.8 a	1.6 bc
Space Stationx	7.7 cd	10.8 c	10.3 cd	21.3 de	0.8 a	1.5 ab
Sunshinez	7.5 cd	10.4 c	9.2 c	20.0 d	0.9 a	1.6 bc
Sweet Mamax	9.1 d	10.8 c	13.5 d	16.6 d	1.1 ab	2.1 d
Thunderx	8.7 d	9.6 c	15.4 d	26.7 e	0.9 a	1.5 bc
P value	<0.0001	<0.0001	<0.0001	<0.0001	<0.0001	<0.0001

^u Common targets for soluble solid levels and dry matter are 6.0 to 7.0 °Brix and at least 9 to 11% dry weight but vary depending on end use and processor requirements.

^v Stokes Seeds, Holland, MI.

^w Column means with a letter in common are not statistically different (Tukey's honestly significant difference; P = 0.05).

^x Rupp Seed, Wauseon, OH.

^y Harris Seeds, Rochester, NY.

^z Johnny's Selected Seeds, Winslow, ME.

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Cultivars Can Be Selected for Crown Rot Resistance and Desirable Fruit Characteristics

Hard squash has a relatively long maturation time compared with cucumber, summer squash, and zucchini. Michigan growers manage Phytophthora blight through a variety of methods, including crop rotation, site selection, raised and plastic-covered plant beds, drip irrigation to deliver fungicides to the plant's crown, and foliar fungicide sprays to protect the fruit. However, growers producing squash for the processing market have small profit margins, making it cost prohibitive for them to implement certain cultural and fungicide recommendations (Hausbeck and Lamour 2004).

Resistance to Phytophthora crown rot has been identified in plant accessions of C. moschata (Chavez et al. 2011; Kousik et al. 2021; Meyer and Hausbeck 2012) and C. maxima (Lee et al. 2001). However, incorporating this resistance into commercial cultivars is difficult because the resistance is governed by the interaction of three independent, dominant genes, R1, R2, and R3 (Padley et al. 2009). At least one C. pepo and five C. moschata germplasm accessions with resistance to Phytophthora crown rot were identified using P. capsici isolates from Florida (Chavez et al. 2011; Padley et al. 2008). Resistance to multiple P. capsici isolates was also identified in the Korean pumpkin cultivar Danmatmaetdol (C. maxima) (Lee et al. 2001). Resistance to P. capsici was identified in the wild species C. lundelliana and introgressed into 19 winter squash breeding lines (Kabelka et al. 2007). We identified four Butternut (C. moschata) cultivars with more resistance to crown rot than Michigan's industry standard NK-580. The Kabocha (C. maxima) cultivar (Thunder) was more resistant to crown rot than Golden Delicious (2020, 2021) and NK-580 (2021).

Ontogenic resistance to fruit rot was previously identified in cucurbits and was specifically investigated in C. moschata cultivars (Ando et al. 2009; Meyer and Hausbeck 2013). C. moschata cultivars develop resistance to fruit rot from 14 to 21 dpp (Alzohairy et al. 2020; Meyer and Hausbeck 2012). Our results show that commercially available C. moschata cultivars also display resistance to crown rot. C. moschata cultivars may require fewer fungicide applications and provide a valuable option for Michigan's processing squash growers struggling to limit Phytophthora blight and maintain processing contracts.

Hubbard-type cultivars are favored, in part, for their ability to achieve the target soluble solids levels of 6.0 to 7.0 °Brix within northern Michigan's growing season (Meyer and Hausbeck 2013). However, success in achieving target Brix levels can vary among years and be influenced by maturity, environmental conditions, and plant stress (Loy 2004). Results suggest that Kabocha-type cultivars exhibiting modest improvements in crown rot resistance (i.e., Thunder) may more consistently exceed targets for soluble solids, along with higher mesocarp dry matter. However, the considerable differences in fruit size, soluble solids, and dry matter relative to the current industry-preferred Hubbard cultivar NK 580 may present challenges for adoption. Among the highly resistant C. moschata cultivars, the larger-fruited Dickinson, Buckskin, and New England Cheddar exhibited low soluble solids (less than 5.3 °Brix) in both years, consistent with previous reports in Michigan (Meyer and Hausbeck 2013). Only the C. moschata cultivar Ultra Butternut consistently met the processor's target for soluble solids, in addition to comparable dry matter and fruit weight, relative to the Hubbard cultivars. Commercial Butternut and Kabocha-type squash cultivars found to have crown rot resistance in this study have potential for use in the Michigan squash-processing industry, but additional evaluation is needed to determine their suitability for production and processing by the state's local growers.