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Samuel Salazar-García, Elizabeth M. Lord, and Carol J. Lovatt

Inflorescence and flower development of the `Hass' avocado (Persea americana Mill.) were investigated at the macro- and microscopic level with three objectives: 1) to determine the time of transition from vegetative to reproductive growth; 2) to develop a visual scale correlating external inflorescence and flower development with the time and pattern of organogenesis; and 3) to quantify the effect of high (“on”) and low (“off”) yields on the flowering process. Apical buds (or expanding inflorescences) borne on summer shoots were collected weekly from July to August during an “on” and “off” crop year. Collected samples were externally described and microscopically analyzed. The transition from vegetative to reproductive condition probably occurred from the end of July through August (end of shoot expansion). During this transition the primary axis meristem changed shape from convex to flat to convex. These events were followed by the initiation of additional bracts and their associated secondary axis inflorescence meristems. A period of dormancy was not a prerequisite for inflorescence development. Continued production of secondary axis inflorescence meristems was observed from August to October, followed by anthesis seven months later. In all, eleven visual stages of bud development were distinguished and correlated with organogenesis to create a scale that can be used to predict specific stages of inflorescence and flower development. Inflorescence development was correlated with minimum temperature ≤15 °C, whereas yield had little effect on the timing of developmental events of individual inflorescence buds. However, the high yield of the “on” year reduced inflorescence number and increased the number of vegetative shoots. No determinate inflorescences were produced during the “on” year. For the “off” year, 3% and 42% of shoots produced determinate and indeterminate inflorescences, respectively.

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Jiwon Jeong and Donald J. Huber

Pre-ripe `Booth 7' avocado (Persea americana Mill.) fruit, a cross of West Indian and Guatemalan strains, were treated with 0.9 μL·L-1 1-methylcyclopropene (1-MCP) for 12 hours at 20 °C. After storage for 18 days in air at 13 °C, at which time whole fruit firmness values averaged about 83 N, half of the 1-MCP-treated fruit were treated with 100 μL·L-1 ethylene for 12 hours and then transferred to 20 °C. 1-MCP delayed softening, and fruit treated with 1-MCP retained more green color than air-treated fruit when full ripe (firmness 10 to 15 N). 1-MCP affected the activities of pectinmethylesterase (EC 3.2.1.11), α-(EC 3.2.1.22) and β-galactosidases (EC 3.2.1.23), and endo-β-1,4-glucanase (EC 3.2.1.4). The appearance of polygalacturonase (EC 3.2.1.15) activity was completely suppressed in 1-MCP-treated fruit for up to 24 days, at which time the firmness of 1-MCP-treated fruit had declined nearly 80% compared with initial values. The effect of exogenous ethylene applied to partially ripened 1-MCP-treated fruit differed for different ripening parameters. Ethylene applied to mid-ripe avocado exerted no effect on the on-going rate or final extent of softening of 1-MCP-treated fruit, even though polygalacturonase and endo-1,4-β-glucanase activities increased in response to ethylene. β-galactosidase decreased in 1-MCP-treated fruit in response to ethylene treatment. 1-MCP delayed the increase in solubility and depolymerization of water- and CDTA (1,2-cyclohexylenedinitrilotetraacetic acid)-soluble polyuronides, likely due to reduced polygalacturonase activity. At the full-ripe stage, the levels of arabinose, galactose, glucose, mannose, rhamnose, and xylose associated with the CDTA-soluble polyuronide fraction were similar among all treatments. In contrast, the galactose levels of water-soluble polyuronides declined 40% and 17% in control and 1-MCP treated fruit, respectively. Hemicellulose neutral sugar composition was unaffected by 1-MCP or ethylene treatment. The data indicate that the capacity of avocado fruit to recover from 1-MCP-mediated suppression of ripening can be only partially amended through short-term ethylene application and differs significantly for different ripening parameters.

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Yaseen Mohamed-Yaseen, Raymond J. Schnell, Robert J. Knight, and T.L. Davenport

A procedure was developed to regenerate plants via tissue culture from embryonic axes of mature avocado seeds. Explants were cultured in Murashige and Skoog (MS) medium supplemented with benzyladenine (BA) and naphthalene-acetic acid (NAA) or thidiazuron (TDZ) and NAA. Culture were kept in the dark for 7-10 days to reduce browning resulting from phenolic oxidation. Multiple shoots (5-8) were formed after transfer to light. Further multiplication were achieved using different combination of BA and NAA or TDZ and NAA. Shoots were cultured in MS supplemented with 2mg/l indolebutyric acid (IBA) for 2 weeks then transferred to MS supplemented with lg/l activated charcoal for root induction. Complete plants were obtained in vitro.

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Julian Mendel, Christina Burns, Beatrice Kallifatidis, Edward Evans, Jonathan Crane, Kenneth G. Furton, and DeEtta Mills

.H.C. Smith, J.A. 2015 Responses of swamp bay, Persea palustris , and avocado, Persea americana , to various concentrations of the laurel wilt pathogen, Raffaelea lauricola For. Pathol. 45 2 111 119 Hughes, M.A. Riggins, J.J. Koch, F.H. Cognato, A. Anderson

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S. L. Ontai, M. L. Arpaia, and J. S. Reints Jr.

In southern California, avocados are often left in the field for up to 12 hours after harvest. Fruit in the bin may reach up to 40C during the summer months and may take up to 24 hours to cool to the recommended storage temperature. A study was conducted using `Hass' avocados over two growing season during the months of July and August to determine the effect of delayed cooling on fruit quality. Fruit were held at 20, 30 or 40 C for 0, 6, 12 or 24 hours before storage at 5C for 0, 2, 4, or 6 weeks. Fruit quality was determined by flesh firmness, time to ripe, vascular and flesh discoloration and the presence or absence of decay. The level of damage seen in storage varied with the harvest. Overall, after 4 or 6 weeks in storage, there was a considerable increase in either vascular or flesh discoloration and decay especially when fruit had been held at 30 or 40C prior to storage. The results indicate that harvested avocados should be kept as cool as possible in the field and that fruit should be processed within 12 hours for storage periods greater than 2 weeks.

Open access

Enrique I. Sánchez-González, Adriana Gutiérrez-Díez, and Netzahualcóyotl Mayek-Pérez

outcrossing rate (t s ), and full siblings rate (t m – t s ) per Mexican race avocado family. Table 4. Analysis of molecular variance for 10 families of Persea americana var. drymifolia based on simple sequence repeat and intersimple sequence repeat

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Salvatore Campisi-Pinto, Yusheng Zheng, Philippe E. Rolshausen, David E. Crowley, Ben Faber, Gary Bender, Mary Bianchi, Toan Khuong, and Carol J. Lovatt

., New York, NY Boldingh, H.L. Alcaraz, M.L. Thorp, T.G. Minchin, P.E.H. Gould, N. Hormaza, J.I. 2016 Carbohydrate and boron content of styles of ‘Hass’ avocado ( Persea americana Mill.) flowers at anthesis can affect final fruit set Sci. Hort. 198 1 125

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Jeremy Burdon, David Billing, and Paul Pidakala

‘Hass’ avocado ( Persea americana ) is the main internationally traded avocado fruit cultivar. With increasing global demand, and increasing numbers of suppliers, increasing volumes of fruit are being shipped between countries. In this global

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Adrian D. Berry, Steven A. Sargent, Marcio Eduardo Canto Pereira, and Donald J. Huber

polysaccharides of avocado ( Persea americana ) fruit Postharvest Biol. Technol. 25 241 256 McGuire, R.G. 1992 Reporting of objective color measurements HortScience 27 1254 1255 Pereira, M.E.C. 2010 Ripening, volatiles and sensory attributes of West Indian and

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Raymond J. Schnell, Cecile L. Tondo, J. Steven Brown, David N. Kuhn, Tomás Ayala-Silva, James W. Borrone, and Thomas L. Davenport

, Fruits and nuts Springer-Verlag Berlin, Heidelberg, Germany Ashworth, V.E.T.M. Clegg, M.T. 2003 Microsatellite markers in avocado ( Persea americana Mill.): Genealogical relationships among cultivated avocado genotypes J. Hered. 94 407 415 Bekey, R. 1986