Predictive Breeding - A New Milestone on the Road of Agricultural Success!

With the advent of genetic engineering, there has been a drastic change in the agricultural techniques. Gone are those days when man used to depend solely on nature for rainfall, soil fertility etc. Modern-man can toy with the genetic sequence and identify the part of genome which is beneficial for him.

                       

An attempt to improve the crop varieties began almost simultaneously with the agricultural practices. Around ten thousand years ago, man started to alter the genetic make up of crops without his knowledge. The conventional plant breeding practices began when early farmers selected the plant with desirable traits and saved its seeds for the next generation. Later with the knowledge of genetics, plant breeders were able to select the crops with desirable traits like faster growth, pest and disease resistance, sweeter fruits, larger seeds etc. Two plants having two different desirable characters were cross-pollinated artificially to obtain an offspring containing a mixture of these characters (hybrid variety). As a net result of these techniques new varieties of crops have developed which are significantly different from their wild relatives. Conventional breeding techniques largely depend on selection of superior varieties of crops and incorporation of desirable traits into future generations.

Genetic engineering has brought quantum change from conventional breeding practices and has introduced combination of genes which do not exist naturally. Sequencing of genomes of various plants has now become feasible with the faster progression in genetic engineering. Predictive breeding is an advanced technique which comes up with a promise of identifying the beneficial genes out of the entire genome. Genetic markers like SNPs (single nucleotide polymorphism) or minisatellites are used to construct linkage maps. The linkage maps help to identify the traits which are inherited together. The knowledge of genome sequence along with the linkage maps helps to associate the beneficial traits of the plant with specific parts of genome sequence.

Complicated genomes of polyploid crops pose a serious problem to predictive breeding. A cell of a polyploidy organism has more than two sets of homologous chromosomes and each set contains all the genes responsible for the biological traits of that organism. Professor Ian Bancroft took this as a challenge and identified the sequence of rapeseed (Brassica napus). This crop has been found to originate from two related species that is Brassica rapa and Brassica oleracea. Rapeseed (Brassica napus) was declared as a third leading source of vegetable oil in the world in the year 2000. Canola is the name given to Canadian oil that is extracted from certain varieties of Rapeseed. This oil is a rich source of essential fatty acids (omega-6 and omega-3 fatty acids in the ratio of 2:1). Apart from these it is also an important source of Biodiesel which can power motor vehicles. This oil is generally combined with fossil-fuel diesel in ratios varying from 2% to 20% of biodiesel. This does not damage the engine. Isn’t it an eco-friendly plant?

Sequencing the DNA of this plant directly was difficult because of its complicated genome. Hence they adopted a different strategy. Transcriptomes were sequenced from young juvenile leaves. Transcriptome is a set of all RNA molecules, including mRNA, rRNA, tRNA, and other non-coding RNA. It represents a small percentage of the genome. The sequence of a transcriptome mirrors the sequence of the DNA from which it was transcribed. This study gives an idea about all the genes which get expressed into proteins in that tissue. Sequence of transcriptome will act like a raw material for scientists struggling to locate the human friendly genes within the entire genome of the polyploid plants. Based on this improved varieties of seeds can be produced.

A large number of crops like potato, wheat, oat, sugarcane, cotton etc are polyploid and few crops amongst them are staple crops in certain parts of the world. Transcriptome sequencing will help the scientists to identify the desirable genes even in the absence of complete genome sequence. This new technique will make predictive breeding of crops with complicated genomes feasible.

Reference:

Bancroft I, Morgan C et al. Dissecting the genome of the polyploid crop oilseed rape by transcriptome sequencing.    Nat Biotechnol. 2011 Jul 31.

Honey! Why do you have such long life?

Honey is fructose rich sweet syrup, which is naturally prepared by honey bees. Honey bees collect the sweet nectar from the plants, refine it with the help of their saliva and regurgitate into the honey comb cells of the beehive. Fanning by the honey bees reduces the water content of honey.

Food substances have a restricted shelf life beyond which they tend to get decomposed and spoilt. Bacteria, fungi and yeasts are the main culprits behind food decay. There are many factors like, temperature, amount of water, pH of food substances etc which decide the rate of growth of these micro-organisms.

Honey is one of the miracle foods and it has been used by human beings since ages. Its world wide use is because of its multifarious benefits with an added longer shelf life. Honey in its raw form is pure and can stay for centuries together. During the excavation of Egyptian pyramids, honeycombs, sealed jars of honey were detected which were not decayed. This is a clear evidence for the fact that pure honey can be preserved for a considerably long period.

A sufficiently long life of honey is by virtue of its unique composition and its physical properties. Chemically honey is made up of 82% of carbohydrates. Fructose (38.2%) is the major monosaccharide in it. Other carbohydrates present in honey are glucose (31%), maltose (7%), and sucrose (1%).  It is rich in amino acid proline, vitamins and antioxidants. Moisture content of pure honey varies between 14%-18%.

Properties which prevent honey from decay are:

• Purity of honey is assessed by its moisture content. Water content below 20% indicates a good quality of honey. This concentration of water is insufficient for the airborne micro-organisms to breed and multiply.
• Honey has a very low pH ranging from 3 to 4.5. Acidic pH inhibits the growth of many micro-organisms.
• A higher concentration of sugar is another primary factor which curtails the growth of micro-organisms. The combination of high sugar concentration and low water content prevents it from getting fermented. Micro-organisms fail to sustain as they get dehydrated by the process of osmosis due to a high concentration of sugar. The same principle is used in the preservation of fruit jams.
• Hydrogen peroxide is produced by the enzyme glucose oxidase present in honey which is competent in inhibiting the microbial growth in honey.
• The percentage of proteins is relatively low. Microorganisms fail to live in such low nitrogenous content.
• Many microorganisms fail to digest fructose which is the major component of honey.

Honey finds a widespread application in our day to day life ranging from food to medicinal and therapeutic use. Its increased shelf life is like an added flavor. Pure honey properly stored in glass or ceramic containers with tight lids can be relished for ages together.

 

 

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Biological Water Purification - Some More Techniques

Palatable clean drinking water is becoming scarce in the present day world. Water table is decreasing day by day and the river water, even after treatment on a community basis, contains many contaminants. The levels of many pollutants like selenium, chromium, cadmium and arsenic have increased in water to dangerous levels. A long-term consumption of these pollutants may damage kidneys, liver and our nervous system. These also could lead to deadly diseases like cancer.

Off late we have different kinds of purifiers available in the market which are available at a very wide range of prices. These purifiers are associated with their own disadvantages, like, some of them consume energy in the form of electricity, some are made up of non biodegradable materials, some are very costly etc.

Some plants have been proved to be excellent for water purification. Plants like the Prickly pear cactus (Opuntia ficus-indica) or Moringa (Moringa oleifera) have the capacity to purify water. The Prickly pear cactus was used for water purification by Mexican communities long back during the 19th-century. As man marched ahead on the roads of civilization these facts were forgotten by him. He started his hunt for high technology methods of water purification.

A group of scientists from the University of South Florida in Tampa rediscovered the natural method of water purification using prickly pear cactus in 2010.

Norma Alcantar and her colleagues have used sophisticated microscopic analysis to prove the effects of cactus on dirty water.

Mucilage is glue like gummy substance secreted by plants which acts as a flocculant in water. It can precipitate substances into flakes and hence can remove substances like heavy metals (selenium, chromium, cadmium and arsenic) and even bacteria from water [1]. This thick gum is used by the plant to store water. When this magical mucilage is added to water, it sticks to the sediment particles and bacteria, which later drops down to the bottom of the water samples. According to Alcantar 98% of added bacteria, Bacillus cereus, was removed from the water sample. However, experiments are yet to be carried in natural water.

Apart from cactus there are some other plants also which help in water purification.

• Drumstick (Moringa Oleifera) – It is a drought resistant tree which can grow on a large number of poor soils including barren land. The seeds of this tree have coagulant properties and can purify turbid contaminated water. The seeds have to be crushed and the paste has to be mixed with water. The water has to be left undisturbed for an hour. The paste coagulates suspended impurities like bacteria, dirt etc and make water ready for domestic consumption. Dust and bacteria settle down which can be later be separated from pure water lying on the top. The protein component of these seeds acts as polyelectrolyte which can cross-link with charged particles.
• Nirmali (Strychnos potatorum) – The seeds of this plant are commonly used to clean water in India.

• Tulasi (Ocimum sanctum) – It is a famous medicinal plant and finds a widespread application in India. The seeds of this plant are also known for their water purification properties. However these seeds can purify water up to a certain extent and make it palatable for domestic purposes.

Many rural and underdeveloped countries have no access to the conventional water purification devices due to which people dwelling there are forced to drink contaminated water. Cactus plant and other plant products can be grown at many places at a lower cost. These plants can serve as a natural and renewable material for water filtration and at the same time save the lives of many people. It is a cost-effective alternative and also saves a lot of energy.

Reference:

Buttice AL, Alcantar NA et al. Removal of sediment and bacteria from water using green chemistry. Environ Sci Technol. 2010 May 1;44(9):3514-9.