Each year, over 3000 acres of bell and nonbell peppers are grown in New Jersey for fresh market and processing [U.S. Department of Agriculture (USDA), 2012]. New Jersey bell pepper production represents about 5.5% of the total U.S. production acreage and has an estimated value of over $12 million (USDA, 2012). Phytophthora capsici, the causal agent of phytophthora blight, causes serious economic losses to many Solanaceae and Cucurbitaceae crops in many vegetable production regions of the United States (Babadoost and Zitter, 2009; Barksdale et al., 1984; Hausbeck and Lamour, 2004). On many vegetable farms in southern New Jersey, P. capsici has become established in fields because of poor crop rotations. The overuse of the Fungicide Resistance Action Committee (FRAC) group 4 fungicide, mefenoxam, has led to the development of mefenoxam-insensitive P. capsici on some vegetable farms in New Jersey and in many other vegetable production regions of the United States (Café-Filho and Ristaino, 2008; Hausbeck and Lamour, 2004; Keinath, 2007; Kline et al., 2011; Parra and Ristaino, 2001). Since P. capsici and mefenoxam insensitivity are both wide spread in the southern vegetable production region of the state, many bell pepper growers have adopted the use of phytophthora-resistant or -tolerant cultivars during the past 15 years. In New Jersey, the use of bell pepper cultivars such as Paladin or Aristotle, both with resistance to the crown rot phase of the pathogen, make up more than 50% of the total annual production acreage. The use of resistant cultivars has been estimated to save growers from 100% loss in some years (Rutgers University, 2005).
Recent research has suggested that P. capsici consists of 14 different races based on differential lines and virulence testing, and suggests that virulence differs in isolates from the same region (Foster and Hausbeck, 2010; Glosier et al., 2008; Sy et al., 2008). Since the early 1990s, researchers in New Jersey have cooperated with commercial seed companies to help determine if specific breeding lines or cultivars exhibit resistance or tolerance to local isolates of P. capsici. Observations made during these evaluations under New Jersey growing conditions have determined that certain cultivars and breeding lines with resistance or tolerance to the crown rot phase of P. capsici have exhibited what is now generically referred to as skin separation, or “silvering,” of bell pepper fruit (Fig. 1). Skin separation reduces aesthetic fruit quality and its presence on fruit can be used to reduce quality grades. Currently, there is no evidence that skin separation reduces shelf life of fresh market fruit or the quality of fruit for processing. Although skin separation was noticed in cultivars and breeding lines during evaluations in the late-1990s and early-2000s, no research was done in New Jersey to determine the potential cause. Only after bell pepper cultivars with tolerance to the crown rot phase of phytophthora blight were commercially released, and appreciable amounts of skin separation developed on bell pepper fruit, did the USDA set guidelines on its allowable limit. Current USDA guidelines label skin separation as a “silvery white discoloration” defect which appears as “diffused or solid silvery white areas” on fruit (USDA, 2016). Because phytophthora-tolerant and -resistant bell pepper cultivars make up more than 50% of the total bell pepper acreage in southern New Jersey, many growers are at risk for reduced quality and grade rejections due to skin separation. In New Jersey, skin separation has been reported to be as high as 66% in some phytophthora-tolerant cultivars at some harvests (Kline et al., 2011). Preliminary research on the possible relationship between the development of skin separation and phytophthora tolerance suggests that genotype may influence the amount of skin separation development in bell pepper fruit (Kline et al., 2011; Wyenandt and Kline, 2006; Wyenandt et al., 2007).
The objectives of this study were to determine the effects of four different production systems and five bell pepper cultivars considered susceptible, tolerant, or resistant to the crown rot phase of P. capsici on the development of skin separation in bell pepper fruit.
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