Ethephon Improved Pigmentation but Had No Effect on Cayenne Pepper
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HORTSCIENCE 48(6):738–741. 2013. because green pods harvested before the breaker stage will not turn red. Pod maturity must be at least to the breaker stage at the time Ethephon Improved Pigmentation of mechanical harvest to ensure proper pod pigmentation. One goal of New Mexico but Had No Effect on Cayenne Pepper growers is to maximize red pod yield, whereas another is to increase red pod percentage, Fruit Yield in Southern New Mexico which will reduce the cost of sorting and removing green pods in a once-over mechan- Mark E. Uchanski1,3 and Adam Blalock2 ical harvest system. Department of Plant and Environmental Sciences, P.O. Box 30003, MSC 3Q, Traditional plant breeding may be another New Mexico State University, Las Cruces, NM 88003 way to improve the efficiency of mechanical harvest and help change the staggered pod Additional index words. Capsicum annuum, chile, controlled abscission, mechanical harvest, development of cayenne. There are culti- synchronize vars that exhibit determinate growth char- acteristics, but the overall quality and yield Abstract. In the desert southwest of the United States, cayenne pepper (Capsicum annuum of these cultivars are inferior when com- L.) is an important crop. It is used in the production of hot sauce mash, the precursor to pared with indeterminate cultivars (Arturo many hot sauces. Because hand harvest is currently required to accommodate staggered Jurado, Jurado Farms, personal communi- crop development, more uniform maturity is desired to facilitate mechanical harvest to cation, 22 Feb. 2009). The release of new decrease labor costs. This study was performed over 3 years (2009–11) and in two determinate cultivars through traditional locations in southern New Mexico, resulting in five unique year/location scenarios plant breeding is time-consuming and costly, (environments). Four timings of ethephon (0.56 kg a.i./ha) spray applications were so this study will focus on managing an evaluated for their potential to increase red cayenne cv. Mesilla yields and percentage of indeterminate hybrid cayenne pepper cultivar red pods. If yield increases and pigmentation improvements occur, ethephon may to synchronize red fruit maturity necessary facilitate a once-over mechanical harvest. Ethephon was applied once at four key cayenne for mechanical harvest. growth stages based on heat units accumulated after planting (HUAP): 1400 HUAP (late One way to manage indeterminant cay- June to early July), 1800 HUAP (mid-July), 2800 HUAP (late August to early September), enne pepper pod maturity is by using plant and 3100 HUAP (mid- to late September). Application timings corresponded to early growth regulators (PGRs). Ethylene, one of bloom, peak bloom, late physiological maturity of plants, and preharvest, respectively. A the primary PGRs involved in fruit ripening, non-sprayed control was also included. Fresh red, green, and non-marketable pod weights has been shown to increase red pod syn- were recorded for each treatment in a once-over simulated machine harvest in October chronization when applied to paprika pepper and analyzed for statistical differences. Mid- to late-season (2800–3100 HUAP) ethephon before harvest at the rate recommended by treatments significantly decreased undesirable green pod yield and, therefore, increased the product (ethephon) label (Kahn et al., red pod percentage in four of five environments. Although a red pod yield increase was only 1997). However, results involving ethephon observed in one environment (a drip-irrigated plot in 2010), there were no negative impacts and fruit maturation are highly variable on red pod yield in any environment resulting from ethephon application. In addition, (Alexander and Grierson, 2002). Ethephon pepper quality (yield of unmarketable pods) was not significantly reduced by ethephon. has been used to enhance the color develop- Previous work has focused on increasing red pod yields with mixed results. The results ment rate in cayenne and paprika peppers show that ethephon may synchronize cayenne pepper red fruit maturity necessary for (Krajayklang et al., 1999), but did not mechanical harvest and reduce the labor involved in removing green pods before improve color development in other pepper processing. cultivars (Hoyer, 1996). When ethephon is used to synchronize red pod development, it is most effective if pods are allowed to Cayenne pepper (Capsicum annuum L.) is are the main ingredient in chile mash, the mature to the breaker stage. Ethephon treat- one of several chile pepper pod types grown precursor to most Louisiana-style hot sauces ments, however, often cause reduced yields in New Mexico. Other pepper pod types in- (Bosland and Strausbaugh, 2010). Many and plant vigor (Kahn et al., 1997). Although clude long red mild, long green mild, paprika, commercial cayenne pepper cultivars have ethephon can boost red pod percentage, it and long green hot [New Mexico Agricultural an indeterminate growth habit and therefore can also cause leaf yellowing and abscission Statistics (NMAS), 2010]. Cayenne peppers each plant has many pods of different ages of young pods and flowers that may reduce that do not ripen to red simultaneously. This the total yield (Kahn et al., 1997). As a re- necessitates multiple, costly hand harvests of sult, many pepper producers have chosen newly matured red pods during the growing not to adopt PGRs as a result of the perceived Received for publication 4 Jan. 2013. Accepted for season (Funk and Marshall, 2012). Increasing risk. publication 12 Apr. 2013. labor costs make it difficult for New Mexico Cantliffe and Goodwin (1975) demon- Funding for this research was provided by the New pepper producers to stay competitive with strated that ethephon applied to paprika-type Mexico Chile Commission. Additional salaries and domestic and foreign markets. Labor costs chile peppers before harvest significantly research support were provided by state and federal funds appropriated to the New Mexico Agricultural have created a shift toward less costly me- increased the ratio of red to green pods. A Experiment Station. chanical harvest (Funk and Walker, 2010). once-over mechanical harvest removes all We acknowledge the technical assistance of Mr. Reducing labor inputs by using mechanical pods from the plant so undesirable green Mike Petersen, Ms. Victoria Frietze, and Ms. Luz harvest technology is one way that New pods must be sorted out later. Therefore, an Hernandez. We also thank Cervantes Enterprises, Mexico producers can maintain a more com- increased ratio of red pods will reduce both Inc. (Vado, NM), Jurado Farms, Inc. (Las Cruces, petitive position in the U.S. and world pepper postharvest sorting time and waste of green NM), and Curry Seed and Chile Company (Pearce, market (Wall et al., 2003b). pods. The practice of applying ethephon be- AZ) for the pepper seed donations. Finally, we In addition to its indeterminate growth fore mechanical harvest could increase the acknowledge Bayer Crop Science for the ethephon habit, cayenne pepper pods have characteristics percentage of red pepper pods; however, donation. We also thank Dr. Chris Cramer for his inputs while preparing the manuscript. indicative of both climacteric and non-climacteric ethephon is not widely used in New Mexico 1Assistant Professor of Horticulture. fruits (Biles et al., 1993; Villavicencio et al., pepper production because results are vari- 2Graduate Research Assistant. 1999). It is therefore designated as semicli- able and, in some cases, treatments actually 3To whom reprint requests should be addressed; macteric. This characteristic of cayenne limits reduce yields (Alexander and Grierson, 2002; e-mail [email protected]. the efficiency of once-over machine harvest Kahn et al., 1997). 738 HORTSCIENCE VOL. 48(6) JUNE 2013 GROWTH REGULATORS Kahn et al. (1997) also proposed that Table 1. Summary of five southern New Mexico (NM) field environments (A–E) at two New Mexico State ethephon applied several weeks before har- University research stations [Fabia´n Garcı´a Science Center (FGSC) and Leyendecker Plant Science vest could increase red pod percentage, Research Center (LPSRC)] near Las Cruces, NM. allowing for a once-over mechanical harvest Environment A B C D E because the number of undesirable green Year 2009 2009 2010 2010 2011 pods is reduced. Cantliffe and Goodwin Research station FGSC LPSRC FGSC LPSRC LPSRC (1975) studied ethephon as a ripening agent Irrigation type Flood Flood Drip Flood Drip z for red pod synchronization, whereas Kahn Soil type Ge Bf Ge Gf Bf et al. (1997) focused on ethephon-induced Replications 3333 4 z abscission of young green pods. Kahn’s re- Source: U.S. Department of Agriculture Natural Resource Conservation Service Web Soil Survey (2009). sults, similar to Cantliffe and Goodwin (1975), Ge = Glendale loam; Bf = Belen clay loam; Gf = Glendale clay loam. suggest that ethephon treatments increased red pod ratio because of significant green pod abscission. However, because of this signif- local practices (Bosland et al., 1999; Walker, 1L·h–1/emitter at 55 kPa. All field environ- icant green pod abscission, total yield was 2009; Wall et al., 2003a; Western Regional ments were irrigated approximately once per reduced (Kahn et al., 1997). Climate Center, 2012). All plots were man- week when the top 5 cm of soil dried. Field As a result of its indeterminant growth aged as uniformly as possible with respect to plots were fertilized once with a urea ammo- habit, we suggest that a midseason applica- water and nitrogen inputs. nium nitrate solution