The popularity of salads and salad mixes has accelerated lettuce’s strong demand among American consumers. The convenience of fresh-cut combined with innovative packaging and the ever-widening product choices of this product bolster lettuce’s position as a top item in produce sales.
The long-standing market for bulk sales continues to grow. Although various types increasingly brighten mainstream and specialty markets, iceberg and romaine remain the most widely produced.
Breeding efforts include the quest for improved color, flavor and shelf life. As with all produce, the need for varieties that can resist or tolerate specific diseases and pests persists.
One program of the Agricultural Research Service (ARS) of the U.S. Department of Agriculture uses genetic approaches suited to this country’s primary lettuce-producing areas: coastal, desert and interior valley locations. Dr. Ryan Hayes says, “Develop landmark cultivars, advanced generation breeding lines and information for use by other breeders, scientists, producers and growers.” This program is developing breeding lines with resistance to bacterial leaf spot, big vein, bolting, Sclerotinia and Verticillium.
Hayes’ ARS program has released three iceberg varieties with resistance to Verticillium race 1. RH05-036, RH-0339 and RH-0340 perform particularly well in the low desert regions. These crosses of La Brillante and Pacific display improvements over their parentage.
Paragon Seed, Inc. has incorporated downy mildew resistance genes from the University of California-Davis into their proprietary lettuce varieties with enhanced resistance to downy mildew and corky root.
Black Belt, a medium-head iceberg introduced for the California coastal areas resists downy mildew strains 1 through 26. Best for summer production, Black Belt excels for food service packs, and for naked or wrapped pack.
Kremlin is a distinct red-leaf lettuce adaptable for warmer growing conditions, coastal and inland summer production in California, and for the early/late harvest in the desert Southwest. With thicker leaves more like iceberg, Kremlin sets a new standard for processors who desire a thick, strong, red leaf that increases shelf life. Extremely bolt-tolerant, it can be used for processing and fresh pack.
Nautilus, a spring or fall medium-sized green romaine, resists lettuce necrotic stunt virus, critical for the coastal areas with increasing levels of infected soil. This medium-green, yellow-interior variety produces a large plant with exceptional weight. Best for cooler growing conditions, yet shows good bolt tolerance.
Two new varieties developed by Pybas Seeds tolerate downy mildew and resist corky root. The plant variety protection (PVP) and the patent number are pending for Journey. Quest has PVP status.
Developed for coastal California, mid to late summer production, medium dark- green Journey yields well. This medium to large-heading iceberg lettuce features sure heading and consistent head shape. It can be harvested about a week sooner than most iceberg varieties. It is corky root-resistant and moderately resists tip burn, as well as provides some tolerance to downy mildew.
Also introduced for coastal California, Quest is a very large-heading, medium dark- green iceberg for early to midsummer production. Its large frame provides ample head coverage to protect from sun and wind. It has some downy mildew tolerance, and resists corky root. With some ability for carton packs, its very large heads make it excellent for bulk harvest.
Rijk Zwaan specializes in fancy European lettuce varieties such as Salanova. The varieties listed here produce well in coastal and desert areas.
Dancine RZ, a medium-green mini butterhead, has strong resistance to internal burn, plus high resistance to red aphid and downy mildew and intermediate resistance to lettuce mosaic virus.
The large 43-15 RZ red butterhead sports ruby coloration down half of its leaves with brilliant green toward the core. Slow-bolting, it is suitable for processor and carton markets. It has high resistance to downy mildew races 1 to 26 and red aphid, and intermediate resistance to lettuce mosaic virus.
Santoro RZ strongly resists internal burn, and has high resistance to downy mildew races 1, 4 to 22, 25, plus red and root aphid, and intermediate resistance to lettuce mosaic virus. This large, light to medium-green butterhead is slow-bolting.
Three new Rijk Zwaan romaines show improved traits. A new open-heart romaine, 41-53 RZ, has more leaves and displays leaves of the same size and width throughout the head. Suitable for the processor and crown markets, it has high resistance to downy mildew races 1 to 15, 17 to 22 and 24 to 26, and intermediate resistance to lettuce mosaic virus. Designed to replace Nirvanus RZ, 41-40 RZ has more resistance to internal burn. It is also highly resistant to downy mildew races 1 through 26 and red aphid. Medium-green, this romaine has an open habit. Very erect, medium-green 41-64 RZ has proven excellent for hearts. This romaine has strong resistance to internal burn, high resistance to downy mildew races 1 to 26 and red aphids, and intermediate resistance to lettuce mosaic virus.
Seminis’ new romaine and iceberg lettuces for the Southwest feature uniformity and varied uses.
Top Billing is highly adaptable to the desert region. Its large, dark- green frame and cap leaves provide excellent protection for its large head. The refined cello appearance makes it suitable for both fresh market and bulk harvest. With excellent uniformity, it has potential for a high harvest packout.
Fast-maturing, uniform Valley Heart suits both early and late- season plantings well. A tall, medium-green romaine with large, slightly savoyed leaves, this variety has good bolt tolerance and excellent packout potential. It performs well for hearts, fresh market and processor use.
Synergene Seed’s breeding efforts focus on the needs of growers, shippers and consumers. These varieties are proprietary and either patented or patent-pending.
Charger, an improved bulk-processing iceberg for bagged salads, has excellent tonnage and weight. Developed for the Southwest desert region, it can be harvested midwinter. With tolerance to big vein, it also has above-average tolerance to bolting and low core.
Del Sol, a very light-green romaine developed for high-temperature growing conditions, has proven excellent for hearts, processing and field packs. It is harvested in the main season of warm coastal and desert areas. It tolerates tip burn, sclerotinia and corky root, plus it has excellent bolting and very low core characteristics.
Very dark green, vigorous and versatile, Green Thunder features good weight potential for cartons and hearts. Introduced for coastal and desert areas, this romaine performs well for main season. Tolerance includes tip burn, sclerotinia and corky root, and it has above average bolt tolerance.
True Heart, a versatile romaine, excels for hearts, processing and field pack cartons. Best in main season, this medium to light green romaine performs well in coastal and desert conditions. It tolerates tip burn and sclerotinia and has above-average bolt tolerance.
Synergene developed Valley Fresh for the desert and coastal areas for the cooler conditions at the front and tail-end of the production season. This medium dark-green romaine has a vigorous habit, and its tall, large frame makes it attractive for hearts or field pack. It has average bolt tolerance, but tolerates both tip burn, corky root and sclerotinia.
Seeds for these varieties are available through their dealers or distributors.
In addition to Ryan Hayes, ARS, Victor Heintzberger, Paragon Seed; Robert Roemling, Pybas Seeds; Karen Marie Feliz, Rijk Zwaan; Jennifer Wahl, Seminis; and Mark Hughes, Synergene Seed, provided information for this column.
The author is a writer-researcher specializing in agriculture. She currently resides in central Pennsylvania.