For nearly three decades the ‘Athena’ melon (Cucumis melo L.) has dominated the eastern shipper cantaloupe market for its uniform quality and proven performance across a broad range of production areas. ‘Athena’ has thick and firm flesh, coarse netting, and slight sutures or ribbing, along with resistance to Fusarium wilt and powdery mildew (Sygenta 2022). We report the development of a new eastern shipper cantaloupe ‘Triton’ that combines powdery mildew and Fusarium wilt resistance with improved fruit quality. In comparison with ‘Athena’, ‘Triton’ has very similar agronomic and aesthetic qualities, but with a significantly smaller seed cavity and improved flavor.
Throughout early domestication, cantaloupe was selected for shape, less-bitter flesh, larger and fewer seeds, and larger fruit (Robinson and Decker-Walters 1997). Cantaloupe breeding in America began through the selection of the green flesh–type cultivar ‘Rocky Ford’ by George W. Swink in 1887 (Smith Farms n.d.). Development of disease-resistant cultivars began in the 1930s, and the first F1 hybrid was introduced in 1955 (Robinson and Decker-Walters 1997).
Significant progress has been made in the past century with regard to disease resistance breeding, notably against Fusarium wilt and powdery mildew. Fusarium wilt in melon is caused by the soil-borne pathogen Fusarium oxysporum f. sp. melonis (Fom) and is widely regarded as one of the most devastating soil-borne diseases (Leach and Currence 1938; Wechter et al. 1995; Zuniga et al. 1997). The genus Fusarium is one of the most important groups of fungal plant pathogens because it causes various diseases within nearly every economically important plant species. Members of this species exhibit genetic plasticity and cause destructive diseases across a diverse spectrum of hosts, including banana, cotton, canola, melon, and tomato. This broad host range is facilitated by horizontal chromosome transfer that leads to host-specific pathogenicity (Ma et al. 2010). Four races of the fungus are pathogenic on melons: 0, 1, 2, and 1.2 (Risser et al. 1976). The most common symptoms include slow wilt with progressive yellowing, and the leaves develop a slight violet color with longitudinal brown necrotic streaks on stems from which gum oozes. Another response to the disease is sudden wilt without prior yellowing or symptoms, and the tips of stems shrivel as the wilt progresses toward the base of the plant. Both types of wilt display light-brown discoloration in the attacked vessels (Bletsos and Thanassoulopoulos 2002). Fusarium wilt causes devastating yield losses up to 100% in infected fields (Sherf and MacNab 1986). Fom can survive in soil as chlamydospores for decades and can colonize the roots of crops grown in rotation with melon, thereby reducing disease protection from crop rotation (Banihashemi and deZeeuw 1975; Joobeur et al. 2004).
Several sources of race-specific genetic resistance have been identified in melon (Joobeur et al. 2004; Oumouloud et al. 2013; Wechter et al. 1995; Zink and Thomas 1990). Resistance to race 1 is conferred by a dominant allele of the gene Fom-2 and resistance to race 2 is conferred by Fom-1, with both genes conferring resistance to race 0 (Risser et al. 1976; Zink and Thomas 1990). Fom-3 confers resistance to races 0 and 2 in cultivar Perlita-FR, but allelism with Fom-1 is unclear (Zink and Gubler 1985). At least three additional minor quantitative trait loci have also been characterized (Branham et al. 2018). Resistance to race 1.2 is quantitative (Nakazumi and Hirai 2004; Perchepied et al. 2005).
Powdery mildew of melon, caused by Podosphaera xanthii (formerly Sphaerotheca fuliginea Schlech ex Fr. Poll.) and Golovinomyces cichoracearum (formerly Erysiphe cichoracearum DC ex Merat), became a problem in the United States suddenly in 1925 (Jagger 1926). Serious economic losses resulted from reduced marketable yield and fruit quality. Resistant varieties, notably ‘PMR 45’, were soon being deployed to combat the fungus (Jagger and Scott 1937). Resistance did not prove durable, and by 1938 a second race had emerged and a new source of resistance had to be identified (Jagger et al. 1938). Powdery mildew resistance breeding has been an active area of research by commercial melon-breeding programs ever since. Today, as many as 46 races of powdery mildew and dozens of resistance genes have been described (Dogimont 2011; McCreight 2006; McCreight et al. 2012). The relationship between these races and resistance genes remains poorly understood.
Origin
‘Triton’, tested as EWS-MLN-070, was developed in Florida as a collaboration between EarthWork Seeds and Eckerd College. Initially, an ‘Athena’ F1 hybrid was self-pollinated to create an F2 population (Fig. 1). Between Spring 2015 and Fall 2018, pedigree breeding with marker-assisted selection was performed on an ‘Athena’ F2 population to develop several stable inbred lines selected for Fom-1, Fom-2, and Pm-2 resistance genes. Molecular marker screening for resistant alleles of Fom-1 and Fom-2 was performed by Ag-Biotech (Monterey, CA) using proprietary DNA markers. Disease screening in the greenhouse and field confirmed resistance to powdery mildew and all common races of Fusarium wilt. Test crosses were made with promising inbreds, and an initial hybrid performance trial was conducted in Florida in 2017 at Hyatt Farms in Lake Wales, FL. One hybrid in particular, derived by crossing a monoecious ‘Tuscan’ melon tester line belonging to EarthWork Seeds with an andromonoecious ‘Athena’-derived inbred developed in collaboration with Eckerd College, was identified based on agronomic (yield, disease resistance) and quality (fruit appearance, texture, and flavor) parameters. This hybrid was sent out to trialing partners in 2018 and 2019 in multiple locations in the United States (Alabama, Arizona, California, Colorado, Florida, Illinois, Massachusetts, Maine, New York, Oregon, Pennsylvania, Virginia, Vermont, Washington, and Wisconsin) as well as Australia and the United Kingdom. Based on positive customer feedback, this hybrid was selected for commercialization. The name ‘Triton’ was selected in reference to two schools affiliated with the authors: Eckerd College’s Triton mascot (St. Petersburg, FL) and Triton Regional High School (Byfield, MA). The use of this name was cleared by the US Department of Agriculture (USDA) in Dec 2018.
Development of ‘Triton’. Schematic depicting the lineage of ‘Triton’. Several generations of self-pollination and selection for disease resistance were followed by hybridization with a Tuscan-type melon to produce the hybrid ‘Triton’ melon.
Citation: HortScience 57, 9; 10.21273/HORTSCI16571-22
Development of ‘Triton’. Schematic depicting the lineage of ‘Triton’. Several generations of self-pollination and selection for disease resistance were followed by hybridization with a Tuscan-type melon to produce the hybrid ‘Triton’ melon.
Citation: HortScience 57, 9; 10.21273/HORTSCI16571-22
Development of ‘Triton’. Schematic depicting the lineage of ‘Triton’. Several generations of self-pollination and selection for disease resistance were followed by hybridization with a Tuscan-type melon to produce the hybrid ‘Triton’ melon.
Citation: HortScience 57, 9; 10.21273/HORTSCI16571-22
Materials and Methods
Fusarium screen.
The fungal inoculation protocol was performed as described by Zink (1992). Melon lines used in fungal screens were provided by EarthWork Seeds and the USDA. Fusarium oxysporum f. sp. melonis race 1 and race 2 fungal strains were received from the USDA Animal and Plant Health Inspection Service in Colorado.
The Fusarium race 1 and race 2 strains were cultured on potato dextrose agar and left to grow at 23 °C for 3 to 4 d. After fungal growth, 10 mL of sterile water was added to the starter culture and agitated into a crude suspension. Spore count of this suspension was quantified using a hemocytometer. A dilute V8® solution (Campbell’s Soup Company, Camden, NJ, USA) was made by combining 100 mL of V8 juice strained through four layers of cheesecloth with 400 mL of distilled water and 1.5 g of calcium carbonate, and autoclaved for 20 min at 121 °C. The V8 solution was inoculated with about approximately 500 µL of the crude suspension. The flasks were incubated at 30 °C for 6 to 7 d with shaking. Subsequently, the inoculum was strained and diluted to the desired concentration of 1.0 × 106 spores/mL using dilute V8.
Seeds were planted into growing inserts (two seeds per 50-mL cell) filled with potting mix (Sungro Promix-Bx; Premier Tech Horticulture, Quakertown, PA, USA). Seedlings were culled to one per cell in the cotyledon stage. Ten-day-old seedlings were inoculated. Two reps of inoculated seedlings were kept in a growth chamber (Conviron Adaptsis CMP6010 and CMP6050; Controlled Environments Limited, Winnipeg, Canada) at 20 to 27 °C, 52% humidity, and 12 h of light. Plants were fertilized using a half-strength foliar spray of Miracle-Gro All Purpose plant food (Scotts Co LLC, Marysville, OH, USA) 10 d after inoculation. Scoring began 28 d postinoculation, and plants were scored on a scale of 1 to 9 points, with 1 point = no symptoms and 9 points = dead. Symptoms included yellowing, necrosis, wilting, and stunting (Fig. 2).
The ‘Triton’ hybrid carries robust resistant to Fusarium oxysporum f. sp. melonis race 1 and 2, and powdery mildew of melon. Photos of 4-week-old melon plants after inoculation with F. oxysporum f. sp. melonis race 1 (A) or race 2 (B). (Left to right) ‘Triton’ [resistant (R) check line], ‘Athena’ (R), ‘MR1’ (R), ‘TopMark’ [susceptible (S) check line], and ‘Charentais T’ (S). (C) Leaves from plants susceptible to powdery mildew (top) in comparison with ‘Triton’ (bottom) under disease pressure in the field in Oviedo, FL.
Citation: HortScience 57, 9; 10.21273/HORTSCI16571-22
The ‘Triton’ hybrid carries robust resistant to Fusarium oxysporum f. sp. melonis race 1 and 2, and powdery mildew of melon. Photos of 4-week-old melon plants after inoculation with F. oxysporum f. sp. melonis race 1 (A) or race 2 (B). (Left to right) ‘Triton’ [resistant (R) check line], ‘Athena’ (R), ‘MR1’ (R), ‘TopMark’ [susceptible (S) check line], and ‘Charentais T’ (S). (C) Leaves from plants susceptible to powdery mildew (top) in comparison with ‘Triton’ (bottom) under disease pressure in the field in Oviedo, FL.
Citation: HortScience 57, 9; 10.21273/HORTSCI16571-22
The ‘Triton’ hybrid carries robust resistant to Fusarium oxysporum f. sp. melonis race 1 and 2, and powdery mildew of melon. Photos of 4-week-old melon plants after inoculation with F. oxysporum f. sp. melonis race 1 (A) or race 2 (B). (Left to right) ‘Triton’ [resistant (R) check line], ‘Athena’ (R), ‘MR1’ (R), ‘TopMark’ [susceptible (S) check line], and ‘Charentais T’ (S). (C) Leaves from plants susceptible to powdery mildew (top) in comparison with ‘Triton’ (bottom) under disease pressure in the field in Oviedo, FL.
Citation: HortScience 57, 9; 10.21273/HORTSCI16571-22
Powdery mildew screen.
Selection for powdery mildew resistance was performed on both parental lines of ‘Triton’ using genotypic and phenotypic methods. Genotyping was performed by Ag-Biotech (Monterey, CA) using publicly available markers (Zhang et al. 2013). Phenotypic selection was performed each generation of self-pollination during the development of the parental lines. The selection environment was in a greenhouse, first in Florida and later in Costa Rica, generally with heavy disease pressure. Powdery mildew resistance was confirmed under agricultural conditions during the hybrid trialing phase in dozens of melon trials in multiple locations in the United States over 4 years of trialing. Powdery mildew resistance is shown compared with the susceptible variety ‘Hale’s Best Jumbo’ in a Florida melon trial (Fig. 2C).
Consumer preference study.
A blind preference study with 90 participants was performed with ‘Triton’, ‘Athena’, and store-bought, long-shelf-life Harper-type melons at Eckerd College in May 2019 (Fig. 3). No background information was provided to the participants. Three stations were constructed for participant assessment: 1) whole melon of each type, 2) halved melon of each type, and 3) blind taste test. At each station, the participants were instructed to rank each melon on a scale from 1 to 3 points, with 1 point = most preferred. At the stations for whole and half melons, participants were encouraged to evaluate the fruit as they would in a commercial setting, such as picking up the fruit, smelling it, or performing any physical evaluation they would in a store. Both the whole and halved melon stations contained four samples of each melon (four halves or four whole). For the taste test, a melon baller was used to make uniform 1-inch (2.54-cm) samples. Participants were provided unflavored salted potato chips to eat in between sampling and were permitted to taste as many times as they needed to make a determination of their preference. For all three stations, the melons were unlabeled and randomized to ensure anonymous data collection. Participants were debriefed after submitting their preference survey.
Consumer preferences favor ‘Triton’. Mean rank of preference for ‘Triton’, ‘Athena’, or the long shelf life Harper-type melon traits included whole melon, halved melon, and taste. A higher mean rank indicates greater preference. ‘Triton’ was significantly more preferred over ‘Athena’ and Harper when inspected visually as a whole melon and in taste. There was no statistically significant difference in preference for the halved melon trait. Letters indicate statistical differences at α = 0.05.
Citation: HortScience 57, 9; 10.21273/HORTSCI16571-22
Consumer preferences favor ‘Triton’. Mean rank of preference for ‘Triton’, ‘Athena’, or the long shelf life Harper-type melon traits included whole melon, halved melon, and taste. A higher mean rank indicates greater preference. ‘Triton’ was significantly more preferred over ‘Athena’ and Harper when inspected visually as a whole melon and in taste. There was no statistically significant difference in preference for the halved melon trait. Letters indicate statistical differences at α = 0.05.
Citation: HortScience 57, 9; 10.21273/HORTSCI16571-22
Consumer preferences favor ‘Triton’. Mean rank of preference for ‘Triton’, ‘Athena’, or the long shelf life Harper-type melon traits included whole melon, halved melon, and taste. A higher mean rank indicates greater preference. ‘Triton’ was significantly more preferred over ‘Athena’ and Harper when inspected visually as a whole melon and in taste. There was no statistically significant difference in preference for the halved melon trait. Letters indicate statistical differences at α = 0.05.
Citation: HortScience 57, 9; 10.21273/HORTSCI16571-22
Statistical analyses.
The R package lme4 was used for linear mixed model analysis of the consumer preference data (Bates et al. 2015). The participants’ rank was converted to a preference scale of 1 (most preferred) to 3 (least preferred), where a rank of 1 = a score of 3, rank 2 = a score of 2, and rank 3 = a score of 1. Estimated marginal means for preference scores were estimated using the R package emmeans (version 1.6.0) (Lenth 2021). The R package multcomp was used to conduct pairwise comparisons across the three cultivars within each trait (whole melon, halved melon, and taste), with a significance level of 0.05 (Hothorn et al. 2009). Results were visualized using the R package ggplot2 (Wickham, 2011). Tukey multiple pairwise comparisons were used to analyze fruit physical characteristics at a significance level of 0.05.
Description and Performance
‘Triton’ combines powdery mildew and Fusarium wilt resistance with a smaller seed cavity, firmer flesh, and higher average Brix reading. The fruit of ‘Triton’ has orange flesh, moderately dense netting, and lacks sutures (Fig. 4A). The fruit is visually comparable to ‘Athena’, without significant differences in size or shape, but with the benefit of having more edible flesh as a result of its statistically smaller seed cavity (Fig. 4B, Table 1). The fruit under Florida growing conditions had an average weight of 2288 g, a length of 18.0 cm, and width of 15.8 cm (Table 1). The average seed cavity diameter was 6.6 cm, in comparison with ‘Athena’s’ 7.6 cm. The flesh had an average of 11.48°Brix and a penetrometer measurement of 1.66 kgf/cm2. In a blind preference study including ‘Triton’, ‘Athena’, and a long-shelf-life Harper type, participants significantly preferred the taste and visual appearance of whole ‘Triton’ fruit over ‘Athena’ and Harper (Fig. 3). Triton is resistant to all three races of Fusarium wilt and powdery mildew, as confirmed through marker-assisted selection and phenotypic screening in the field and greenhouse (Fig. 2).
‘Triton’ melon. (A) Photo of ‘Triton’ melon. (B) Cross section of ‘Triton’, ‘Athena’, and Harper-type melons (left to right) comparing seed cavity and rind size.
Citation: HortScience 57, 9; 10.21273/HORTSCI16571-22
‘Triton’ melon. (A) Photo of ‘Triton’ melon. (B) Cross section of ‘Triton’, ‘Athena’, and Harper-type melons (left to right) comparing seed cavity and rind size.
Citation: HortScience 57, 9; 10.21273/HORTSCI16571-22
‘Triton’ melon. (A) Photo of ‘Triton’ melon. (B) Cross section of ‘Triton’, ‘Athena’, and Harper-type melons (left to right) comparing seed cavity and rind size.
Citation: HortScience 57, 9; 10.21273/HORTSCI16571-22
Physical characteristics of ‘Triton’, ‘Athena’, and long-shelf-life Harper melons.
Availability
Seeds are currently available from Johnny’s Selected Seeds (www.johnnyseeds.com/).
Literature Cited
Banihashemi, Z. & deZeeuw, D.J. 1975 The behavior of Fusarium oxysporum f. sp. melonis in the presence and absence of host plants Phytopathology 65 1212 1217
Bates, D., Kliegl, R., Vasishth, S. & Baayen, H. 2015 Parsimonious mixed models arXiv 1506.04967. [accessed 14 Jul 2022.]. https://doi.org/10.48550/arXiv.1506.04967
Bletsos, F. & Thanassoulopoulos, C. 2002 The effect of Verticillium and Fusarium wilts on the growth of four melon (Cucumis melo L.) cultivars Phytopathol. Mediterr. 41 279 284
Branham, S.E., Levi, A., Katawczik, M., Fei, Z. & Wechter, W.P. 2018 Construction of a genome-anchored, high-density genetic map for melon (Cucumis melo L.) and identification of Fusarium oxysporum f. sp. melonis race 1 resistance QTL Theor. Appl. Genet. 131 4 829 837 https://doi.org/10.1007/s00122-017-3039-5
Dogimont, C 2011 2011 Gene list for melon Rep. Cucurbit Genet. Coop. 33 104 133
Hothorn, T., Bretz, F. & Hothorn, M.T. 2009 The multcomp package R Foundation for Statistical Computing Vienna, Austria
Jagger, I 1926 Powdery mildew of muskmelon in the Imperial Valley of California in 1925 Phytopathology 16 1009 1010
Jagger, I.C. & Scott, G.W. 1937 Development of powdery mildew resistant cantaloup No. 45 US Department of Agriculture Washington, D.C
Jagger, I.C., Whitaker, T.W. & Porter, D.R. 1938 A new biologic form of powdery mildew on muskmelons in the Imperial Valley of California Plant Dis. Rep. 22 275 276
Joobeur, T., King, J.J., Nolin, S.J., Thomas, C.E. & Dean, R.A. 2004 The Fusarium wilt resistance locus Fom-2 of melon contains a single resistance gene with complex features Plant J. 39 3 283 297 https://doi.org/10.1111/j.1365-313X.2004.02134.x
Leach, J.G. & Currence, T.M. 1938 Fusarium wilt of muskmelons in Minnesota University of Minnesota, Agricultural Experiment Station Minneapolis, Minnesota, USA
Lenth, RV 2021 Estimated marginal means, aka least-squares means [R Package Emmeans Version 1.6. 0] Comprehensive R Archive Network (CRAN)
Ma, L.-J., van der Does, H.C., Borkovich, K.A., Coleman, J.J., Daboussi, M.-J., Di Pietro, A., Dufresne, M., Freitag, M., Grabherr, M., Henrissat, B., Houterman, P.M., Kang, S., Shim, W.-B., Woloshuk, C., Xie, X., Xu, J.-R., Antoniw, J., Baker, S.E., Bluhm, B.H., Breakspear, A., Brown, D.W., Butchko, R.A.E., Chapman, S., Coulson, R., Coutinho, P.M., Danchin, E.G.J., Diener, A., Gale, L.R., Gardiner, D.M., Goff, S., Hammond-Kosack, K.E., Hilburn, K., Hua-Van, A., Jonkers, W., Kazan, K., Kodira, C.D., Koehrsen, M., Kumar, L., Lee, Y.-H., Li, L., Manners, J.M., Miranda-Saavedra, D., Mukherjee, M., Park, G., Park, J., Park, S.-Y., Proctor, R.H., Regev, A., Ruiz-Roldan, M.C., Sain, D., Sakthikumar, S., Sykes, S., Schwartz, D.C., Turgeon, G.B., Wapinski, I., Yoder, O., Young, S., Zeng, Q., Zhou, S., Galagan, J., Cuomo, C.A., Kistler, H.C. & Martijn, R. 2010 Comparative genomics reveals mobile pathogenicity chromosomes in Fusarium Nature 464 367 373 https://doi.org/10.1038/nature08850
McCreight, J.D 2006 Melon–powdery mildew interactions reveal variation in melon cultigens and Podosphaera xanthii races 1 and 2 J. Am. Soc. Hortic. Sci. 131 59 65 https://doi.org/10.21273/JASHS.131.1.59
McCreight, J.D., Coffey, M.D., Sedláková, B. & Lebea, A. 2012 Cucurbit powdery mildew of melon incited by Podosphaera xanthii: Global and western U.S. perspectives 181 189 Sari, N., Solmaz, I. & Aras, V. Proc. Cucurbitaceae 2012. Cukurova Univ. Antalya, Turkey
Nakazumi, H. & Hirai, G. 2004 Diallel analysis for resistance of melon (Cucumis melo) to Fusarium wilt caused by Fusarium oxysporum f. sp. melonis race 1,2y Ikushugaku Kenkyu 6 2 65 70 (in Japanese)
Oumouloud, A., El-Otmani, M., Chikh-Rouhou, H., Claver, A.G., Torres, R.G., Perl-Treves, R. & Álvarez, J.M. 2013 Breeding melon for resistance to Fusarium wilt: Recent developments Euphytica 192 2 155 169 https://doi.org/10.1007/s10681-013-0904-4
Perchepied, L., Dogimont, C. & Pitrat, M. 2005 Strain-specific and recessive QTLs involved in the control of partial resistance to Fusarium oxysporum f. sp. melonis race 1.2 in a recombinant inbred line population of melon Theor. Appl. Genet. 111 1 65 74 https://doi.org/10.1007/s00122-005-1991-y
Risser, G., Banihashemi, Z. & Davis, D.W. 1976 A proposed nomenclature of Fusarium oxysporum f. sp. melonis races and resistance genes in Cucumis melo Phytopathology 66 9 1105 1106
Robinson, R.W. & Decker-Walters, D.S. 1997 Cucurbits CAB International Wallingford, UK
Sherf, A.F. & MacNab, A.A. 1986 Vegetable diseases and their control Wiley New York, NY
Smith Farms n.d. History: Early cantaloupe history http://rockyfordmelons.com/history/cantaloupe-history/. [accessed 9 Jul 2022]
Sygenta 2022 Melon: Vegetable seed http://www.syngenta-us.com/seeds/vegetables/melon. [accessed 9 Jul 2022]
Wechter, W.P., Whitehead, M.P., Thomas, C.E. & Dean, R.A. 1995 Identification of a randomly amplified polymorphous DNA marker linked to the Fom 2 fusarium wilt resistance gene in muskmelon MR-1 Mol. Plant Pathol. 85 10 1245 1249
Wickham, H 2011 ggplot2 Wiley Interdiscip. Rev. Comput. Stat. 3 2 180 185
Zhang, C., Ren, Y., Guo, S., Zhang, H., Gong, G., Du, Y. & Xu, Y. 2013 Application of comparative genomics in developing markers tightly linked to the Pm-2F gene for powdery mildew resistance in melon (Cucumis melo L.) Euphytica 190 157 168 https://doi.org/10.1007/s10681-012-0828-4
Zink, F.W 1992 Genetics of resistance to Fusarium oxysporum f. sp. melonis races 0 and 2 in muskmelon cultivars Honey Dew, Iroquois, and Delicious 51 Plant Dis. 76 2 162 166
Zink, F.W. & Gubler, W.D. 1985 Inheritance of resistance in muskmelon to Fusarium wilt J. Am. Soc. Hortic. Sci. 110 600 604
Zink, F.W. & Thomas, C.E. 1990 Genetics of resistance to Fusarium oxysporum f. sp. melonis races 0, 1, and 2 in muskmelon line MR-1 Phytopathology 80 11 1230 1232
Zuniga, T.L., Zitter, T.A., Gordon, T.R., Schroeder, D.T. & Okamoto, D. 1997 Characterization of pathogenic races of Fusarium oxysporum f. sp. melonis causing Fusarium wilt of melon in New York Plant Dis. 81 6 592 596 https://doi.org/10.1094/PDIS.1997.81.6.592
