The center of origin of wild avocado (Persea americana Mill.) is considered to be the humid tropical highlands of Central America (Honduras, Guatemala, and southern Mexico), and the three subspecies/races appear to have evolved in different climatic environments isolated from each other geographically (Kopp, 1966; Litz et al., 2005; Scora et al., 2002). Persea americana var. drymifolia race Mexican evolved in the highlands of south-central Mexico and is adapted to tropical highlands (semitropical climate). P. americana var. guatemalensis race Guatemalan is adapted to medium elevations in the tropics and, therefore, prefers subtropical climate. Lastly, P. americana var. americana race West Indian (or Antillean) is adapted to the lowlands and humid subtropics and, therefore, grows best in tropical areas (Litz et al., 2005; Popenoe, 1935). California and other regions with similar climates grow mostly Guatemalan and Guatemalan–Mexican hybrid avocados adapted to cooler winter temperatures. These avocados have a rough, leathery exocarp but the edible mesocarp portion has smooth texture with high oil content, up to 30% for some cultivars; the predominant cultivar on the market, ‘Hass’, is of this type (Barmore, 1976; Gibson, 1984; Lee et al., 1983; U.C. Riverside Avocado Database, 2016). On the other hand, the south Florida avocado industry grows cultivars that are better adapted to tropical climates with West Indian and West Indian–Guatemalan hybrid backgrounds (Crane et al., 2013; Litz et al., 2005). However, those types are less rich tasting because of lower oil content, have reduced shelf life, and have limited consumer acceptance compared with Guatemalan/Mexican types (Litz et al., 2005). Therefore, finding a Guatemalan or Guatemalan–Mexican hybrid adapted to Florida’s subtropical climate would widen choices for Florida’s avocado industry and potentially permit production in areas where avocado has not been commercially produced.
Avocado fruit do not ripen while on the tree and only begin to ripen after harvest, making it difficult to identify fruit that are physiologically mature. There is a correlation between oil content and dry weight, with both increasing during maturation while fruit are still on the tree (Lee et al., 1983; Ozdemir and Topuz, 2004; Ratovohery et al., 1988). California maturity standards have been developed based on this correlation: a minimum of 20.8% dry matter content is required for ‘Hass’, with permitted harvest dates from 28 Nov. to 16 Jan., depending on the size (Anonymous, 1925; California Avocado Commission, 2016; Lee, 1981; Obenland et al., 2012). However, in Florida, maturity standards based on oil content or dry matter are not reliable because of the overall low oil content of West Indian avocados. A 1% or 2% variation in oil content could be critical for the maturity of some cultivars (Barmore, 1976). Furthermore, variability among cultivars and varietal differences in accumulation rates make maturity standards based only on oil content impractical in Florida. Instead, maturity standards are variety-specific, based on minimum fruit weight or diameter, or minimum days from full bloom (Barmore, 1976; Harding, 1954; Thurman and Campbell, 1959).
‘Hass’ is the most important avocado in the world with many traits that make it a favorite of growers, merchants, and consumers. Unfortunately, like most cultivars with Guatemalan and Mexican backgrounds, it does not perform well in south Florida avocado-producing areas. Disease pressure from high humidity, combined with insufficient chill hours, often do not allow adequate fruit yield. It would be very useful to identify a ‘Hass’-like cultivar that is well adapted to Florida as it would find a ready market. Because avocado produces hundreds of flowers for every fruit produced, conventional controlled crosses are very inefficient and largely impractical. As ‘Bacon’ is the primary pollinizer for ‘Hass’ (Kobayashi et al., 1996; Vrecenar-Gadus and Ellstrand, 1985), we acquired seeds and identified true hybrids for planting and evaluation. No comparable populations were available, but hybrids of this cross appear to be an adequate population for producing the type of selection we are targeting. Therefore, the objective of this project was to assess promising progeny from reciprocal crosses of ‘Hass’ and ‘Bacon’ in an attempt to identify a ‘Hass’-like selection suitable for east-central Florida. A preliminary sensory study was conducted in 2013 and indicated good acceptance of fruit from these hybrids grown at the Fort Pierce USDA farm (Pisani et al., 2014). In the current 2-year study, selections exhibiting good horticultural and postharvest qualities were identified and tested in sensory panels using store-bought ‘Hass’ as the standard. Attributes assessed included dry matter and lipid content to determine whether these hybrids would meet California standards for avocado maturity when grown in east-central Florida.
Anonymous 1925 Standardization committee report California Avocado Association annual report. California Avocado Association, Pasadena, CA. p. 46–47
Barmore, C.R. 1976 Avocado fruit maturity, p. 103–109. In: J.W. Sauls, R.L. Phillips, and L.K. Jackson (eds.). Proceedings of the First International Tropical Fruit Short Course: The Avocado. Fruit Crops Dept., Florida Cooperative Extension service, Institute of Food and Agricultural Sciences, Univ. of Florida, Gainesville
Bora, P.S., Narain, N., Rocha, R.V.M. & Paulo, M.Q. 2001 Characterization of the oils from the pulp and seeds of avocado (cultivar: Fuerte) fruits Grasas Aceites 52 3–4 171 174
California Avocado Commission 2016 <http://www.californiaavocadogrowers.com/industry/maturity-release-dates>.
Crane, J.H., Douhan, G., Faber, B.A., Arpaia, M.L., Bender, G.S., Balerdi, C.F. & Barrientos-Priego, A.F. 2013 Cultivars and rootstocks, p. 200–233. In: B. Schaffer, B.N. Wolstenholme, and A.W. Whiley (eds.). The avocado: Botany, production and uses. 2nd ed. CABI, Boston, MA
Du Plessis, L.M. 1979 Seasonal changes in the composition of avocado oil recovered by centrifugation. South African Avocado Growers’ Assn. Res. Rpt. 3 74 79
Gibson, A.C. 1984 The guacamole tree. In: Writeups and illustrations of economically important plants. 23 Mar. 2016. <http://www.botgard.ucla.edu/html/botanytextbooks/economicbotany/Persea/index.html>.
Kobayashi, M., Henderson, D., Davis, J. & Clegg, M.T. 1996 Outcrossing in avocado: Is there a relationship to fruit yield? California Avocado Soc. Yrbk. 80 63 74
Kopp, L. 1966 A taxonomic revision of the genus Persea in the western hemisphere (Perseae-Lauraceae) Mem. New York Botan. G. 14 1 120
Lee, S.K., Young, R.E., Schiffman, P.M. & Coggins, C.W. Jr 1983 Maturity studies of avocado fruit based on picking dates and dry weight J. Amer. Soc. Hort. Sci. 108 390 394
Litz, R.E., Witjaksono,, Raharjo, F., Efendi, D., Pliego-Alfaro, F. & Barceló-Muñoz, A. 2005 Persea americana avocado, p. 326–347. In: R.E. Litz (ed.). Biotechnology of fruit and nut crops. 1st ed. CABI, Cambridge, UK
Menge, J.A. & Ploetz, R.C. 2003 Diseases of avocado, p. 35–71. In: R.C. Ploetz (ed.). Diseases of tropical fruit crops. CABI Publishing, Cambridge, MA
Moreno, A.O., Dorantes, L., Galíndez, J. & Guzmán, R.I. 2003 Effect of different extraction methods on fatty acids, volatile compounds, and physical and chemical properties of avocado (Persea americana Mill.) oil J. Agric. Food Chem. 51 2216 2221
Obenland, D., Collin, S., Sievert, J., Negm, F. & Arpaia, M.L. 2012 Influence of maturity and ripening on aroma volatiles and flavor in ‘Hass’ avocado Postharvest Biol. Technol. 71 41 50
Ozdemir, F. & Topuz, A. 2004 Changes in dry matter, oil content and fatty acids composition of avocado during harvesting time and post-harvesting ripening period Food Chem. 86 79 83
Pacetti, D., Boselli, E., Lucci, P. & Frega, N.G. 2007 Simultaneous analysis of glycolipids and phospholipids molecular species in avocado (Persea americana Mill) fruit J. Chromatography 1150 241 251
Pisani, C., Ritenour, M.A., Stover, E., Plotto, A., Gutierrez, O.A. & Kuhn, D. 2014 California avocados in Florida? Finding the perfect avocado for production in east-central Florida Proc. Fla. State Hort. Soc. 127 131 134
Pisani, C. 2016 Exploring avocado variability for laurel wilt resistance and excellent fruit quality and horticultural traits for production in East-Central Florida. Univ. of Florida, Gainesville, PhD Thesis
Ploetz, R.C., Zentmyer, G.A., Nishijima, W.T., Rohrbach, K.G. & Ohr, H.D. 1994 Compendium of tropical fruit diseases. 1st ed. The American Phytopathological Soc., St. Paul, MN
Ratovohery, J.V., Lozano, Y.F. & Gaydou, E.M. 1988 Fruit development effect on fatty acid composition of Persea americana fruit mesocarp J. Agr. Food Chem. 36 2 287 293
Schnell, R.J., Tondo, C.L., Brown, J.S., Kuhn, D.N. & Ayala-Silva, T. 2009 Outcrossing between ‘Bacon’ pollinizers and adjacent ‘Hass’ avocado trees and the description of two new lethal mutants HortScience 44 1522 1526
Scora, R.W., Wolstenholme, B.N. & Lavi, U. 2002 Taxonomy and botany, p. 15–37. In: B. Schaffer, B.N. Wolstenholme, and A.W. Whiley (eds.). The avocado: Botany, production and uses. 1st ed. CABI, Boston, MA
Thurman, T.H. Jr & Campbell, C.W. 1959 Evaluation of indices for Florida avocado maturity Proc. Annu. Meet. Fla. State Hort. Soc. 72 349 353
U.C. Riverside Avocado Database 2016 20 Mar. 2016. <http://ucavo.ucr.edu/avocadovarieties/avocadovarieties.html>.
Vrecenar-Gadus, M. & Ellstrand, N.C. 1985 The effect of planting design on out-crossing rate and yield in the ‘Hass’ avocado Sci. Hort. 27 215 221
White, A., Woolf, A., Hofman, P. & Arpaia, M.L. 2009 The international avocado quality manual. 1st ed. Plant and Food Research, New Zealand
Yahia, E.M. & Woolf, A.B. 2011 Avocado (Persea americana Mill.), p. 125–185. In: E.M. Yahia (ed.). Postharvest biology and technology of tropical and subtropical fruits Volume 2: Açai to citrus. 1st ed. Woodhead Publishing, Cambridge, UK