In New York, cauliflower production was estimated at a value of $2.6 million on a total of 470 acres in 2014 [U.S. Department of Agriculture (USDA), 2015a]. Although the majority of cauliflower production occurs in California and Arizona, there is still strong interest in cauliflower production in New York State especially with the local food movement and consumers’ interest in locally grown produce (USDA, 2015b). Cauliflower is an excellent cool season crop for New York vegetable growers and has recently increased in popularity. The consumption of cauliflower increased to 1.9 lb per capita for 2014 from 1.7 lb per capita in 2013 (USDA, 2015c). Little is known about how different cauliflower varieties perform in New York State, as each growing region has unique factors such as disease pressure and climate conditions that influence how varieties perform.
One of the main foliar diseases affecting cauliflower and other brassica crops such as cabbage (Brassica oleracea var. capitata), brussels sprout (B. oleracea var. gemmifera), and kale (B. oleracea var. acephala) is alternaria leaf spot caused by the fungus Alternaria brassicicola. The disease causes lesions on the leaves and curd resulting in a damaged and unmarketable crop. Alternaria brassicicola thrives under cool, moist conditions which typically occur in the fall during the primary cauliflower growing season for New York State. Optimal conditions for sporulation of A. brassicicola include a relative humidity of at least 87% and temperatures between 20 and 30 °C (Humpherson-Jones and Phelps, 1989). Alternaria leaf spot starts as pinpoint brown or black specks on the leaves, which enlarge to form circular lesions with concentric rings creating a distinct bull’s eye lesion or target spot as seen in Fig. 1A. The black specks can also appear on the cauliflower curds and can enlarge over time as seen in Fig. 1B. These unsightly black specks can greatly reduce the quality and marketability of the curd.
For a cauliflower curd to be considered the highest grade (USDA No. 1), spots, “when added together cannot exceed that of a circle three-eighths of an inch in diameter” (USDA, 1968). Cauliflower curds must not only be free from disease but also from abnormalities known as fuzziness and riciness, with a minimum diameter of 4 inches (USDA, 1968). Some abnormalities seen in cauliflower are the result of temperature changes after curd initiation.
Curd initiation typically occurs when cauliflower plants reach maturity defined by a critical number of leaves along with an exposure to cooler temperatures or vernalization period (Hand and Atherton, 1987). Wurr et al. (1993) determined that the vernalization period for summer and autumn cauliflower occurs between 9 and 21 °C. Changes in temperatures after curd initiation can result in abnormalities such as fuzziness and riciness. Fuzziness, also referred to as bracting, occurs when small leaves, which can be white in appearance, appear in the curd giving an overall fuzzy appearance to the curd as seen in Fig. 1C. Fuzziness occurs as the result of high temperatures (above 15 °C) just after curd initiation (Grevsen et al., 2003). Riciness, another abnormality, occurs when small flower buds form on the surface of a curd and is the result of high temperatures in combination with low temperatures early in curd development (Grevsen et al., 2003). Grevsen et al. (2003) found that cauliflower plants grown at 20 °C followed by a treatment of 8 °C resulted in 100% riciness. Cauliflower quality and yield is influenced by temperature, and each variety can perform differently under various conditions. Growers need to know how cauliflower performs under various temperatures and disease prevalence to plant the appropriate varieties for their field site. The objective of the present study was to evaluate commercially available cauliflower varieties for yield, quality, and susceptibility to alternaria leaf spot under New York field conditions.
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