BIOTECHNOLOGY ASSISTED PLANT BREEDING - SOLUTION FOR FEEDING THE WHOLE LOT OF PEOPLE

SOME DISHEARTENING FACTS:

Ø  The total population of the world is 7.046 billion in 2012.

Ø  The growth rate is 1.2% per year.

Ø  Global cereal utilization in 2013/14 is projected to be 2,413 million tons, 3.2 percent higher than in 2012/13.

Ø  Agricultural land area is decreasing rapidly and is the major challenge for feeding   the whole world.

Ø  About 800 million people go to bed hungry daily.

Ø  About 1.5 billion people (i.e.) almost one fifth of the total people earn less than a dollar per day.

Ø  Human population will be around 11 billion by 2100.

Ø  If the same trend continues then inevitably more people will be starving to death. On an average, for every two seconds one person losses his life due to starvation.   

So, something has to be done in order to overcome this sad state of billions. Only solution is to enhance the breeding strategy of agricultural crops.

I feel that it’s time for novel biotechnological approaches to assist breeding. The acceptance and wide usage of Marker Assisted Breeding is a positive sign. But sadly only variations, rather only the superior traits/QTLs/genes that occur naturally can be exploited.

Another approach, ‘TRANSGENIC SCIENCE’ has to be exploited. Unfortunately, due to unawareness about the safety and efficiency of this novel strategy, its usage is limited to only a few countries.

The take home message from this piece of information is to “create awareness about the efficiency of biotechnology (especially transgenics)  in order to achieve the dream of feeding the whole world with quality food.”

     

                                               

Importance of Marker Assisted Doubled Haploid line development

In vitro selection techniques –– Use of doubled haploids in crop improvement

The ultimate objective of plant breeding is to feed the whole lot of humans with quality food. In making this dream to become true there are many challenges,

Ø The growth rate of human population is 1.2%                         per year.

Ø Agricultural area is decreasing rapidly every                           year.

So the issue is crystal clear, the only way out is to develop strategies to breed the plants to produce ample amount high quality food grains in ever decreasing agricultural area and ever increasing population.

Limitations of conventional Plant breeding:

Conventional plant breeding involves in the production of superior plants simply by breeding the elite variety with a donor plant which has superior traits (QTL/gene/trait), but might not have ideal agronomic traits.

The selection of superior plants is a very critical event in plant breeding. In conventional plant breeding the following limitations are faced,

Ø  Attainment of complete homozygosity and homogeneity takes a long time. Generally, about seven to eight generations are required for the achievement of stable population.

Ø  The process of selection is very tedious as the plants are selected based on morphology.  

 

In order to overcome these issue Marker Assisted Doubled Haploid technique has been developed.

Production of haploid plants:

The phenomenon of exploiting totipotency and culturing of single/group of plant cells or callus in vitro is called Plant tissue culture.

The haploid plants are raised through anther culture, microspore culture, ovary /ovule culture.

The anther culture is generated in the following way,

The anther is emasculated from a healthy F1 plant, selected based on the presence of tightly linked markers.

Ø  The isolated anthers are cultured in vitro in an appropriate growth media.

Ø  The regenerated plant is haploid in nature.

Ø  Colchicine is used to double the chromosome number.

Mode of action of Colchicine:

The effect of colchicine on the course of mitosis is entirely specific, and the modification in mitotic behavior is called C-mitosis (colchicine modified mitosis).

Ø  The c-mitosis is referred to one single moment, inactivation of the spindle apparatus connected with a delay of the division of the centromere.

Ø  The effect thus produced may be expressed as a completion of the chromosome mitosis without nuclear or cellular mitosis.

Ø  The prophase stages take place normally: the chromosomes divide, condense, and assume metaphase appearance. They are however, not arranged into an equatorial plate. Instead they are all the time scattered over the cell in a diakinesis-like manner.

Ø  In this manner DH plants are generated.

Factors affecting anther culture:

In microspore/anther culture,

Ø  Condition of the donor plant is of critical importance.

Ø  Timing of isolation of the anther.

Regeneration can be obtained by direct embryogenesis or via callus stage and subsequent embryogenesis.

The final product obtained through anther culture is a haploid plant. Superior genotypes are selected by checking for the presence of tightly linked marker. Chromosomes are doubled for the selected plants alone. Complete population stability can be attained in the first  generationitself.

Applications of DH in transgenic science:

Transgenic science involves in the introduction of GOI into a host plant to generate superior genotypes.

DH lines serve the following functions in transgenic science,

Ø  The integrated GOI can be easily transferred to the progenies.

Ø  All the plants in the progeny would possess the GOI.

DH lines – plant breeding:

Ø   Reduction in  the variety development time span, or "time to market (TTM)”

Ø   Doubled haploids allow breeders to stabilize desired traits in a single year, reducing the time required for new variety development by up to five years.  

Despite several advantages, there are certain limitations also,

Ø  Although doubled haploidy is useful in fixing rare alleles, overuse may reduce genetic variation.

Ø  Lack of genotype independent growth media.

The take home message is that the DH line complemented with MAS is an effective means of producing superior varieties/hybrids in one generation time itself.