Crop Improvement Through Tissue Culture

Abstract

Techniques developed for plant tissue culture and micropropagation are important enabling technologies that should help meet the demand for more efficient agricultural and horticultural production in the next decades. An overview of in vitro propagation and regeneration via meristem, cell, tissue and organ cultures, organogenesis and somatic embryogenesis is presented. New methods and developments in protoplast isolation and culture, hairy root culture and transfer of genes in transgenic plants are covered. These technologies could significantly simplify breeding programmes and overcome some important agronomic and environmental traits that would not be achievable through conventional breeding and propagation. Tissue culture protocols are available for most crop plants, although continued optimisation of culture media and growth conditions is still required for many crops, especially some cereals and woody plants. Tissue culture methods, in combination with molecular techniques, have been successfully used to incorporate specific traits through direct gene transfer and subsequent culture.

In vitro techniques for culture of protoplasts, anthers, microspores, ovules and embryos have been used to introduce new genetic variation into breeding lines via haploid plant production. Cell culture has also produced somaclonal and gametoclonal variants with crop improvement potential. The culture of single cells and meristems can be used to eradicate pathogens from planting stocks and improve yields of existing cultivars. Large-scale, commercial micropropagation laboratories are providing millions of plants for agricultural planting and synthetic seeds; however a better understanding of the cost–benefit analysis of tissue culture is required. Biopharming of plants with significant advantages in cost and safety is regarded as a promising platform for the production of complex pharmaceutical proteins and metabolites. The present review summarises advances made in this area of hairy root mediated biotransformation and exogenous substrate production. However, low product synthesis remains a major obstacle that limits extensive commercialisation of plant bioproduction technology. Bioinformatic and molecular data indicates that miRNAs control expression of a large proportion of important genes, and this review discusses some representative examples of this. Transgenic approaches provide a powerful tool for gene function investigations in plants. However, some legumes are still recalcitrant to current transformation methods, limiting the extent to which these agriculturally important transgenic plants can be utilised.