Pepper (Capsicum annuum) is an important crop worldwide, with an estimated 25% of people consuming some form (vegetable, spice, or food colorant) of pepper daily (Smith, 2015). Originating in the Americas, peppers have been widely adopted into the cuisines of Africa, Asia, and Europe (Guzman et al., 2011; Sherman and Billing, 1999; Smith, 2015). In 2014, global harvested area of pepper was ≈3,600,000 ha, with the vast majority (≈65%) of production occurring in Asia (Food and Agriculture Organization of the United Nations, 2015). Peppers are a high-value crop (DeWitt and Bosland, 1993) and have short-term economic benefits for smallholder farmers (Kahane et al., 2013). Peppers are also important sources of provitamin A compounds (Guzman et al., 2011; Kantar et al., 2016) and vitamin C; thus, they have long-term nutritional benefits.
Pepper production occurs across a broad range of agroecological conditions, including the humid tropics, deserts, and cool temperate climates (Bosland and Votava, 2012), and different systems ranging from open field to protected cultivation (sweet pepper). Productivity of pepper is often reduced by both biotic and abiotic stresses, the types of which can vary greatly among region. High-yield, disease-resistant cultivars are one of the most effective ways for farmers to increase productivity. Although no cultivar of a given crop is adapted everywhere, cultivars differ in the extent of their adaptation. A major objective of most breeding programs is high and stable yield and yield components. Breeders must examine whether a given cultivar is better adapted to a specific type of environment, and whether its performance is stable relative to that of other cultivars. Predictable performance over a broad range of conditions benefits farmers and seed producers by expanding the range of adaptation, and increased uniformity and potential sales. Consequently, potential cultivars are evaluated over locations and/or years to assess cultivar adaptation. G × E interaction is a major concern in cultivar development, testing, and release. This interaction occurs when the relative performance of genotypes changes in different environments. Partitioning of environments to reduce G × E interaction is challenging, especially in areas where there is extensive climatic variation.
Consumer preference of pepper is region specific and can vary greatly within a country (Bosland and Votava, 2012). Although studies in this area are limited, it has been observed that regional-specific preferences for pepper fruit shape, size, and color, and capsaicinoid content, as well as yield, are major driving forces for farmer cultivar selection. Similarly, for pepper, yield components include fruit length, fruit width, and fruit weight, among other traits. Therefore, evaluating the stability of yield and yield components of multiple market types in diverse environments is essential for successful pepper breeding. Unfortunately, studies to evaluate G × E interaction in Capsicum generally have focused on accumulation of capsaicinoids (Butcher et al., 2012; Gurung et al., 2011; Lee et al., 2005; Zewdie and Bosland, 2000) and not on the stability of yield or yield components (Gurung et al., 2012; Zewdie and Poulos, 1996). The World Vegetable Center (WorldVeg) pepper breeding program seeks to combine superior traits into broadly useful backgrounds of hot peppers for use in diverse production regions around the world. Adaptation to warm, humid climates; high yield potential; yield stability; and multiple disease resistance are the key breeding goals. Acceptable fruit shape, size, heat, and flavors are also critically important for adoption. Breeding activities and line development are carried out in Taiwan.
The ICPN at WorldVeg was initiated during the early 1990s as a platform to distribute sets of improved pepper lines to interested cooperators around the world, and as an opportunity to gather performance data from diverse ecological settings. Nursery participants volunteer to conduct the trial and have the opportunity to evaluate new pepper lines, and to identify those that have potential as new cultivars or as parents in localized breeding programs. The multilocation data of ICPN can provide valuable information on G × E interactions that can be used in improving pepper cultivar development and testing programs. The additive main effect and multiplicative interaction (AMMI) analysis can be an effective model to assess stability of genotypes because it captures a large portion of the G × E sum of squares and allows for the separation of main and interaction effects, providing meaningful interpretation of the data (Pacheco et al., 2016).
Our objectives were to characterize the presence and relative magnitude of genotype, environment, and G × E interaction in the ICPN15 and to evaluate the performance and stability of entries in the ICPN15, while determining the utility of publicly available meteorological data as a tool to determine the effects temperature and precipitation play on the stability of yield in pepper.
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