Current Progress In Agricultural Biotechnology For Crop Improvement

2018-02-04 10:31:22



Agricultural biotechnology has made significant contribution in the past twenty years encompassing within its fold the spectacular developments in plant molecular biology and genetic engineering. Development of efficient procedures such as Agrobacterium mediated transformation and particle bombardment to introduce foreign genes in plant cells led to the genetic transformation of all major crop species. A variety of important traits have been introduced in plant species. There has been priority to reorient our research programmes relating to transgenic research in crops on the basis of the national importance. Biotechnology, in agriculture, is a powerful and immensely useful tool to keep pace with the ever burgeoning population for meeting the food and nutritional security and meeting the challenge of escalating biotic and abiotic stresses. The technology is also well-poised to enhance farm prosperity besides augmenting the cause of health, environment and livelihood of the people.

Genes and promoters isolation

Availability of suitable genes and promoters is vital for a meaningful transgenic programme that can be pursued to a logical conclusion.  Earlier most of the genes and promoters that are commonly used/ commercialized in the past are linked with IPR issues. In addition, many of the genes/promoters that are useful in agricultural biotechnology programmes have now been isolated in developed countries.  Considerable amount of research has been carried out so far using various genes obtained from such programmes. However, in the past decade, a few laboratories in India isolated genes that are useful for imparting insect resistance protein quality, abiotic stress tolerance etc., such genes include synthetic genes encoding Bt-endotoxins and wild type genes encoding storage proteins, protease inhibitors, lectins and enzymes/proteins related to osmotolerance and grain quality traits.  It is expected that more genes will be mined in the next few years based on the sequence information generated from Arabidopsis and rice genomes. However the promoters available are inadequate, especially for the expression of foreign genes in monocots.  Modified CaMV 35S promoters, meristem and seed-specific promoters are available in a few laboratories.  Constitutive promoters such as CaMV 35S also have limitations of expression in reproductive tissues or during senescence.  Prospecting for strong constitutive and tissue specific promoters is imperative. Some of the important areas under genes & promoters research are:

  • Genes from plant sources that impart insect pest resistance
  • Modification of genes encoding Bt insecticidal proteins
  • Genes involved in protein quality and vitamin biosynthesis
  • Genes responsible for abiotic stress tolerance
  • Genes for disease (viral and fungal) resistance
  • Isolation of powerful constitutive and tissue specific promoters
  • Development of suitable constructs for plant genetic transformation

Plant transformation systems 

In vitro culture and regeneration of plants is the prerequisite for modifying plants through genetic engineering. Routine procedures are now available for genetic transformation of many crop species including monocotyledonous species.  However, a few important crops such as cotton, chickpea, pigeonpea, mungbean etc., remain different. Although standard procedures are available for transformation and regeneration of different crop plants, large scale transformation programs have not been taken up in many laboratories, especially in public research system.  Limitations to embark upon such exercises need to be addressed.

The present methods of transformation do not permit targeted insertion of the transgene into host chromosome.  Similarly, the number of transgenic copies inserted is also highly variable.  On average, 2.5 copies of transgene are inserted even with Agrobacterium mediated transformation.  Ideally single copy transgenic plants are needed.  Thus majority of the transgenic plants produced will prove to be associated with some or the other negative effect.  Hence, to produce commercially viable transgenic crops very large number of independent transgenic plants will need to be generated, analyzed and evaluated. Some of the agriculturally important crop plants such as wheat, rice, maize, chickpea, pigeonpea, cotton, groundnut, etc. are extremely recalcitrant to regeneration in vitro tissue culture and thus to genetic transformation.  Therefore, a greater focus should be on the development of regeneration and transformation protocols in economically important crops such as wheat, rice, maize, cotton, pigeonpea, chickpea, groundnut, sorghum, millets which are crops of poor farmers.

Development of transgenic crops and their commercialization

Transgenic crops expressing foreign gene, which confer, added protection against insect pests and viruses could make a significant contribution to provide sustainable agricultural in the future. It is clear that biotechnology is paving the way to develop transgenic varieties with enhanced productivity as well as improved nutritional quality. The modern approaches therefore will hasten the process of agricultural development in our country.

Current global status of transgenic crops

There are five general types of transgenic plants: those with genes to improve the quality of the product, those with genes to allow them to resist disease, insect pests, plants with genes that allow them to be resistant to the effects of herbicides, as well as plants with genes conferring resistance to environmental conditions that cause crop losses (extremes of cold, heat, drought, salt concentration, etc.). A developing group of transgenic plants is that of nutraceuticals, or plants designed to possess properties that make them healthier in specific ways i.e. plants that produce higher concentrations of specific compounds like lycopene or b-carotene. An emerging class of transgenic plants increasingly created by modern methods, known as pharmacrops, aims to use plants to manufacture other products, such as pharmaceuticals and industrial chemicals. In recent years, development of transgenic crops expressing a variety of novel traits such as insect resistance, disease resistance, herbicide tolerance, hybrid production, improved oil quality etc have led to large scale cultivation of transgenic crops (genetically modified crops) which currently occupy 125 million hectare or more precisely 166 million “trait hectares” on a global scale (2008). The number of countries planting biotech crops increased to 23 and comprised 12 developing countries and 11 developed countries. The very high adoption rate by farmers reflects that biotech crops have consistently performed well and delivered economic benefits to small and large farmers in developing and industrial countries. It is also noteworthy that in 2008, India, the largest Cotton growing country in the world registered the highest proportion increase in Bt. Cotton area to 7.6 million hectares. In 2008, the US, followed by Argentina, Brazil, Canada, India, and China continued to be the principal adopters of biotech crops globally, with 62.5 million hectares planted in the US (50% of global biotech area) of which approximately 52% were stacked products containing two or three traits. The stacked products, currently deployed in the US, Canada, Australia, Mexico, South Africa and the Philippines, are an important and growing future trend, which meets the multiple yield constraints of farmers. Biotech soybean continued to be the principal biotech crop in 2008, occupying 65.8 million hectares (53% of global biotech area), followed by maize (37.3 million hectares at 30%), cotton (15.5 million hectares at 12%) and canola (5.9 million hectares at 5% of global biotech crop area). The increasing collective impact of the five principles developing countries is an important continuing trend with implication for the future adoption and acceptance of biotech crops worldwide. Each of the five countries have benefited in a different way from biotech crops.

Transgenic research status in India

Current R&D in crop biotechnology in India is focused on the biotechnology crops that can contribute to higher & more stable yields and enhanced nutrition. The current research and development activities in transgenic research in India have led to the generation of a number of transgenic plants harboring genes of agronomic as well as quality traits. The transgenics in cotton (Bt-cotton hybrids), engineered for tolerance to insect damage have been already released for commercial cultivation in 2002. In the year 2002, first transgenic crop planting of Bt cotton was cultivated in about 50,000 ha in India. Presently, about 6.2 million hectare (2008) area is estimated to be under approved Bt cotton hybrids. The institutions under the ICAR, DST, DBT and CSIR have established a large number of facilities where most advanced transgenic research is being done. In the identification of new genes relating to biotic and abiotic stress, quality trait, development of new drug delivery systems, diagnostics, recombinant vaccines, computational biology, and many other related areas, considerable success has been achieved.