IN VITRO REGENERATION OF TRECULIA AFRICANA DECNE. FROM EMBRYO EXPLANTS ON THE MEDIA OF MURASHIGE AND SKOOG (MS) AND GAMBORG ET AL. (B5)

ABSTRACT

The effect of three different concentrations of sucrose namely 2, 3 and 4% were investigated on the in vitro regeneration of embryo explants of Treculia africana Decne. on the media of Murashige and Skoog (MS) (1962) and Gamborg et al. (B5) (1968) respectively without any growth regulator. The experimental design was a 2 x 5 factorial in a completely randomized design with each treatment consisting of ten replicates. Results showed that while both media including  control supported  the in vitro  regeneration  of T. africana  embryo  explants,  B5 medium was found to be  significantly superior (P≤0.05) to MS medium in all the growth parameters studied.  B5  medium at 4% sucrose elicited the best response in all the growth parameters determined while control gave the least response. The protocol reported here can be used for large scale propagation of true-to-type T. africana plants within a short time for the   purpose of   improvement through genetic transformation (mutagenesis) and   the development of a viable conservation programme.

CHAPTER ONE

INTRODUCTION

There  are  approximately  400,000  species  of higher  plants,  of  which  250,000  have  been identified or described (FAO 1996). Among them, some could be described as endangered, rare, vulnerable or endemic and all these are of plant genetic resource (PGR) conservation concern to the country considering the unprecedented rates of occurrence in comparison with normal natural history rate (Ogbu et al., 2010).   . The  causes of the loss of our plant bio resources in general have been identified to include overexploitation, massive deforestation, and desertification, paucity of institutional frame work to engage in deliberate conservation of PGR relevant to food and agriculture/forestry,  inadvertent emphasis on more exotic crop species/ varieties to the neglect of our useful indigenous plants etc. (Ogbu et al., 2010). Given the combined effort of these deleterious factors, genetic erosion becomes inevitable where no deliberate effort is made to forestall it (Petters, 2000).

Treculia africana Decne. (African bread fruit, Wild jack fruit, or African boxwood), is  an important multipurpose indigenous tree species in Africa belonging to the taxonomic family Moraceae.  The  tree  serves  for  the  provision  of  nutritive  food  for  the  local  population. Analysis  of the hexane  extract  of the seeds indicates  that it contains  a  stearine  solid  fat fraction, resembling that of palm kernel oil and an aleine fraction with a composition similar to that of cotton seed oil; carbohydrate  content 40-50% starch,  3-8% glucose and a good protein content with its lysine 50% higher than that of soya beans and methionine content

1.65% as in soya beans Nutrecul Agroforestry Company (N A C, 2013),. Lyseine is the most limiting amino acid of all vegetable protein; therefore, T. africana seems to have an important role in those  regions  that have a shortage  of good protein  sources  and  especially  where kwashiorkor appears.

Despite the dietary and economic importance of African breadfruit, it has remained an under- utilized species till now and its potentials remain under-exploited. This problem is capable of causing  serious  threat of erosion of its genetic  resources  as well as  extinction  threat.  T. africana is currently included in the list of endangered species of Southern Nigeria (Meregini,

2005) and this is quite worrisome.  The underutilization  has been caused by a number  of reasons. Firstly, increase in population pressure especially in the urban places due to rural- urban migration. The increased population is resulting in the conversion of more forests to agricultural  lands, industrial  estates and homes in order  to satisfy the basic  needs (food, clothing and shelter) of the teeming population. Currently, erstwhile village fruit tree forests which served as sanctuaries for in situ and some degree of ex situ  conservation of choice plants  in several  communities  are now being shared  out to  community members  for the purpose of agricultural  production  and even being sold  or  leased  out to companies.  The thinking of the village heads is that the establishment of such companies in their domain will provide jobs for their subjects as well as bestow development on their communities. This is however to the contrary often-times  as  rather  than assisting to actualize  the development dream, most of these companies end up exploring and over-exploiting the natural resources in these areas and degrade the  land through unsustainable  exploitation (resulting in grave consequences) which leave the people highly vulnerable to environmental shocks (Nuga and Ofodile,  2010).  The   Niger  Delta  region  of  southern  Nigeria  is  currently  having  this experience.   FAO (2005) reported that Nigeria has the world‘s highest deforestation rate of primary  forests  and  a  further  report,  FAO  (2006)  revealed  that  the  country  has  lost  a staggering 79% of its old-growth forests between 1990 and 2005.

Added to that, the fully grown trees have such a large size that minority of the people would want to leave it in their compound for food, ornamental or aesthetic purposes. The height of the tree and the fruit on the tree of the unimproved  varieties such that the  fruit cannot be

plucked rather falls downs on its own instills fear in the mind of many. This is because falling down of the fruit head on an individual may cause death or serious injury. South easterners believe that the fruit of the species have some mystical powers which cause  the death of persons the fruit falls on accidentally (Nuga and Ofodile, 2010). It is viewed as a “taboo” for the fruit to fall on a person.  The resultant  effect  of this belief  is the  felling  of African breadfruit trees found in home gardens in spite of the increasing  demand for its products. Also, the long gestation period of ten (10) or more years of the species has not helped matters either. This leads to the second reason which is non-improvement and limited cultivation of the species.

Thirdly,  there is high rate of deforestation due to industrial,  construction  and  agricultural purposes. The heartwood is yellow with very narrow pale sapwood; very dense, fairly elastic and flexible with fine, even structure. This component makes it suitable for paper industries, building,  construction  companies,  carpentry and joinery  (N  A C, 2013).  All these above reasons call for the need of conservation of this species to avoid genetic erosion. Therefore, there is an urgent need for application of a reliable and efficient in vitro system that results in efficient   differentiation,   shoot   development,   and   whole   plant   regeneration   for   the improvement of T. africana through genetic transformation or mutagenesis.

Conservation of plants in the field is often costly and carries high risk of loss due to disease infections,  demographic  and  environmental  variations,  habitat  loss,  genetic  drift,  human disturbances etc. Therefore, the strategies and procedures employed to establish and maintain field collections need to be practical, rational and economic in addition to being scientifically sound (Ogbu  et al., 2010).Most  times, experience  in  field collections lies with individual curators and may not be readily available to guide others. Furthermore, there are methods of using in vitro methods (biotechnological approach) for the conservation of crops normally

conserved  in the  field  (Reed  et al., 2004;  Singh,  2006). In  vitro  cell  and  tissue  culture methodology  is envisaged  as a means  for germplasm  conservation  to  ensure  survival  of endangered plant species, rapid mass propagation for large-scale re-vegetation and for genetic manipulation studies.

Therefore, the aim and objectives of this study are:

•     To develop a protocol for regeneration of Treculia africana from embryonic axis of seed as a prerequisite for improvement through genetic transformation.

•    To compare the effect of two different media i.e. Murashige and Skoog (1962) and

Gamborg et al.(1968)on the growth of embryonic axis of T. africana seed

•     To assess  the effects of different  levels of sucrose on the  germination  of  zygotic embryo of T. africana.

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