AVOCADO – Research & Development

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1. Close Planting of Avocado.

by Bruno Razeto, Jose Longueira, and Thomas Fichet (1992).University ofChile. Casilla 1004,Santiago,Chile.

Abstract. Three planting distances, 6×6, 5.5 x 3 and 4 x 2 m are being tried in an experimental grove of the cv. Bacon planted in 1984. Trees started to form dense hedges five and six years after planting at 4 x 2 and 5.5 x 3 m distances, respectively. Yield per tree started to be proportionally affected by closer distances by the fourth year. However, yield per hectare continued to increase in accordance with tree density up to the sixth year. Individual fruit weight, percent oil and percent dry weight decreased as planting density increased. Nitrogen, phosphorus and zinc content in the leaves decreased as planting density increased. Conversely, calcium and magnesium increased while potassium, iron, manganese and copper were not affected. This progress report covers the first six years of this trial, which is planned for 12 years.

2.   Liver Injury Suppressing Compounds from Avocado(Persea americana)

by Hirokazu Kawagishi, Yuko Fukumoto, Mina Hatakeyama, Puming He,  Hirokazu Arimoto, Takaho Matsuzawa, Yasushi Arimoto, Hiroyuki Suganuma, Takahiro Inakuma, and Kimio Sugiyama (2001). Department of Applied Biochemistry, Faculty of Agriculture, Shizuoka University, 836 Ohya, Shizuoka 422-8529, Japan; Department of Chemistry, Faculty of Science, Shizuoka University, 836 Ohya, Shizuoka 422-8529, Japan; and Research Institute, Kagome Company, Ltd., 17 Nishitomiyama, Nishinasuno-machi, Nasu-gun, Tochigi 329-2762, Japan

Abstract: To evaluate the protective activity of fruits against liver injury, 22 different fruits were fed to rats with liver damage caused by D-galactosamine, a powerful liver toxin. As measured by changes in the levels of plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST), avocado showed extraordinarily potent liver injury suppressing activity. Five active compounds were isolated and their structures determined. These were all fatty acid derivatives, of which three, namely, (2E,5E,12Z,15Z)-1-hydroxyheneicosa-2,5,12,15-tetraen-4-one, (2E,12Z,15Z)-1-hydroxyheneicosa-2,12,15-trien-4-one, and (5E,12Z)-2-hydroxy-4-oxoheneicosa-5,12-dien-1-yl acetate, were novel.

3.   Anticonvulsant effect of Persea americana Mill (Lauraceae) (Avocado)   leaf aqueous extract in mice.

by  Ojewole JA, Amabeoku GJ.( 2006). Department of Pharmacology, School of Pharmacy and Pharmacology, Faculty of Health Sciences, University of KwaZulu-Natal, Private Bag X54001, Durban 4000, South Africa. ojewolej@ukzn.ac.za.

Abstract: Various morphological parts of Persea americana Mill (Lauraceae) (avocado) are widely used in African traditional medicines for the treatment, management and/or control of a variety of human ailments, including childhood convulsions and epilepsy. This study examined the anticonvulsant effect of the plant’s leaf aqueous extract (PAE, 50-800 mg/kg i.p.) against pentylenetetrazole (PTZ)-, picrotoxin (PCT)- and bicuculline (BCL)-induced seizures in mice. Phenobarbitone and diazepam were used as reference anticonvulsant drugs for comparison. Like the reference anticonvulsant agents used, Persea americana leaf aqueous extract (PAE, 100-800 mg/kg i.p.) significantly (p < 0.05-0.001) delayed the onset of, and antagonized, pentylenetetrazole (PTZ)-induced seizures. The plant’s leaf extract (PAE, 100-800 mg/kg i.p.) also profoundly antagonized picrotoxin (PCT)-induced seizures, but only weakly antagonized bicuculline (BCL)-induced seizures. Although the data obtained in the present study do not provide conclusive evidence, it would appear that ‘avocado’ leaf aqueous extract (PAE) produces its anticonvulsant effect by enhancing GABAergic neurotransmission and/or action in the brain. The findings of this study indicate that Perseaamericana leaf aqueous extract possesses an anticonvulsant property, and thus lends pharmacological credence to the suggested ethnomedical uses of the plant in the management of childhood convulsions and epilepsy.

4.   TRANSFORMATION AND CRYOPRESERVATION OF  EMBRYOGENIC AVOCADO (Persea americana Mill.) CULTURES

by  Darda Efendi (2003).  A DISSERTATION PRESENTED TO THEGRADUATESCHOOLOF THEUNIVERSITYOFFLORIDAIN PARTIAL FULFILLMENT  OF THE REQUIREMENTS FOR THE DEGREE OF  DOCTOR OF PHILOSOPHY.UNIVERSITYOFFLORIDA

The avocado fruit is climacteric and ethylene acts as a natural triggering mechanism for the induction of ripening.  Genetic transformation of avocado with a gene construct that could block ethylene biosynthesis would extend on-tree storage and shelf life of avocado fruit.   The samK gene encodes SAM hydrolase, which converts SAM (S-adenosylmethionine) to methylthioadenosine and homoserine so that it is not available for ethylene biosynthesis.

Embryogenic avocado cultures were genetically transformed using an Agrobacterium tumefaciens-mediated protocol.   Transformed embryogenic avocado cultures harboring AGT01/NPTII::ACP/SamK were selected in MS3:1P medium supplemented with 100 to 300 mg l-1  kanamycin sulfate. Further selection was accomplished on somatic embryo development medium supplemented with 200 mg l-1 kanamycin sulfate, which completely inhibits development and maturation of nontransformed somatic embryos.

Embryogenic cultures experience major developmental problems over time, which include a low rate of somatic embryo germination and loss of embryogenic competence. The latter can make it difficult to develop elite lines that have been genetically engineered, and cultures of some genotypes cannot be used for medium-term research.   Long-term storage of embryogenic cultures is critical to address this problem.

Avocado embryogenic cultures can be cryopreserved by slow cooling and vitrification. The ability to withstand cryopreservation appears to be genotype-dependent.   Following cryopreservation, embryogenic cultures can proliferate in liquid medium, and somatic embryo development and germination do not appear to be negatively affected.

This study should have a major impact on biotechnology research involving avocado.  This is the first report of regeneration of transgenic avocado with a horticulturally important trait.  The cryopreservation protocols developed in this study will have major impact on the management of avocado genetic resources and experimental material in the laboratory.

Abstracts: Embryogenic avocado cultures derived from ‘Hass’ protoplasts were genetically transformed with the plant defensin gene (pdf1.2) driven by the CaMV 35S promoter in pGPTV with uidA as a reporter gene and bar, the gene for resistance to phosphinothricin, the active ingredient of the herbicide Finale® (Basta) (Bayer Environmental Science, Research Triangle Park, Durham, NC ). Transformation was mediated by Agrobacterium tumefaciens strain EHA105. Transformed cultures were selected in the presence of 3.0 mg l⁻¹ phosphinothricin in liquid maintenance medium for 3–4 mo. Liquid maintenance medium consisted of modified MS medium containing (per liter) 12 mg NH₄NO₃ and 30.3 mg KNO₃ and supplemented with 0.1 mg l⁻¹ thiamine HCl, 100 mg l⁻¹ myo-inositol, 30 g l⁻¹ sucrose, 3.0 mg l⁻¹ phosphinothricin, and 0.41 μM picloram. Somatic embryo development from transformed cultures was initiated on MS medium supplemented with 45 g l⁻¹ sucrose, 4 mg l⁻¹ thiamine HCl, 100 mg l⁻¹ myo-inositol, 10% (v/v) filter-sterilized coconut water, 3.0 mg l⁻¹ phosphinothricin, and 6.0 g l⁻¹ gellan gum. Limited plant recovery occurred from somatic embryos on semi-solid MS medium supplemented with 3.0 mg l⁻¹ phosphinothricin, 4.44 μM 6-benzylaminopurine (BA), and 2.89 μM GA₃; transformed shoots were micrografted on in vitro-grown seedling rootstocks. Approximately 1 yr after acclimatization in the greenhouse, transformed shoots were air-layered to recover transformed roots. Genetic transformation of embryogenic cultures, somatic embryos, and regenerated plants was confirmed by polymerase chain reaction (PCR), Southern blot hybridization, the XGLUC reaction for uidA, and application of the herbicide Finale® to regenerated plants.

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