Agriculture.ph Blog

The avocado (Persea americana Miller) is one of the promising fruit-bearing trees in the country. However, the avocado industry is hobbled by problems concerning Phytophthora root rot disease.

Phytophthora is a fungus that causes rapid decay of roots and trunk, eventually leading to the death of the infected avocado tree. Presently, there is no known avocado variety in the Philippines that is resistant to this fungus.

Plant breeders have identified biotechnologies to address this problem. One such method is mutation breeding, which is more socially acceptable compared to the controversial genetic engineering. According to the International Atomic Energy Agency (IAEA), more than 2,000 crops have been improved through mutation breeding. Studies have also shown that mutation, tissue culture, and the combination of both can produce plant varieties of new or improved genetic characteristics.

In order to develop a Phytophthora-resistant avocado variety using a combination of biotechnologies, Dr. Renato A. Avenido, Assistant Professor 7 at the Institute of Biological Sciences, College of Arts and Sciences (CAS), and his research team, conducted a project entitled ‘Generation of Variability in Avocado through in Vitro Mutation and Somaclonal Variation.’ The project was conducted at the Plant Cell and Tissue Culture Laboratory of the Institute of Plant Breeding (IPB), College of Agriculture (CA) from December 2001 to January 2005 with Dr. Avenido (then a University Researcher at IPB) as the chief scientific investigator.

In order to apply mutation breeding, the team had to first establish a working micropropagation system for avocado. A micropropagation system is a procedure for rapid multiplication of plants using tissue culture methods.

The study began with the collection of seeds from immature avocado fruits. From the seeds, small portions of plant tissue (embryos) were allowed to grow (embryogenic cultures) and to differentiate into somatic embryos and shoots. Some of the plant tissue cultures were subjected to gamma irradiation at the Philippine Nuclear Research Institute (PNRI) in order to facilitate mutation from the regenerated plant tissue cultures. During the irradiation, some cells were killed and those capable of regrowth were multiplied. The surviving cells were grown to produce somatic embryos and shoots.

The study, funded by the IAEA, an agency working for the peaceful uses of nuclear energy, produced over 400 potential variants and mutants. With this, Dr. Avenido’s group successfully established reproducible tissue culture and gamma irradiation systems for avocado, the first to do so on a woody tropical fruit crop in the Philippines.

In March 2007, the joint CA and CAS project entitled ‘Confirmation, propagation and greenhouse/field establishment of avocado mutants derived from tissue culture and gamma irradiation’ of Dr. Avenido was again funded by the IAEA. The shoots from irradiated and non-irradiated tissues were then treated in a test tube environment to promote root growth and to prepare them for natural growth environment. At present, the team is undertaking the rooting and potting out of the plantlets to enable maximum recovery. The established regenerated plants will then be transferred to the greenhouse, and finally to the field for further evaluation.

Successful propagation of potential mutants will enable subsequent genetic analysis to identify beneficial mutations, and eventually, the release of new and improved varieties of avocado. Not only that, it opens the doors for the same procedures to be undertaken in order to improve other economically important fruit species such as mangosteen, lanzones and selected citrus. This could improve the country’s position as a producer of these highly marketable fruits.

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The paper entitled ‘A Complete Micropropagation System of Avocado from Somatic Embryogenesis to Successful Transplant to Soil and its Application to Mutation Breeding’ that was based on this study received the second prize award in the 2007 AFMA Best Research and Development Paper Award (applied research in agriculture category) given by the Department of Agriculture-Bureau of Agricultural Research on Oct. 6, 2007 at the Manila Hotel. The competition had over a hundred entries from R&D institutions and universities all over the country. Dr. Avenido is the senior author of the paper. His co-authors are Prof. Lilian F. Pateña, Julita G. Dimaculangan, Julieta N. Welgas, Jennelyn M. Carandang, and Dr. Ramon C. Barba.

Written by: EBV Bernardo, Published Dec 2007 in The UPLB Horizon

Source: www.uplb.edu.ph