In the beginning of 20th century, successful attempts were made to develop synthetic wheat during a study to determine progenitors of cultivated wheat. Synthetic wheat is a goldmine for wheat improvement. It has valuable genetic variability for resistance to biotic and tolerance to abiotic stresses.
Wheat is the most important cereal crop of the world. It is not only most widely cultivated crop but also the most ancient crop species. Wheat is the top most consumed cereal of the world, consisting of 30% of cereals worldwide. It has adaptability in diverse environments ranging from sea level to as high as mountain peaks, as in Tibet.
Wheat is cultivated in 43 countries of the world. Based on the area under cultivation, modern wheat is classified into two major types: bread wheat and durum wheat. Bread wheat (Triticuma estivum L.) is a hexaploid (2n=6x=42, AABBDD) and accounts for 95% of the total wheat produced. Durum wheat: (Triticum turgidum var.durum L.) is a tetraploid (2n=4x=28 AABB) and accounts for the remaining 5% of the wheat production.
Why do we need synthetic wheat?
Wheat is an important staple food of around half of the population of the world. As the population of world is increasing the demand of wheat is increasing globally. The current global wheat production is 700 million metric tons (MMT) and expectations are up to 880 MMT by 2050.
Plant breeders and geneticists have always made efforts to produce surplus wheat by using suitable breeding techniques. In 1960s, Green Revolution was a great breakthrough in the improvement of wheat yield. This revolution introduced wheat with short stature, high yield, high input responsive, and better resistance to environmental stresses.
However, domestication and successive use of these wheat cultivars in breeding programs has narrowed down their genetic base that has lead to gradual genetic erosion and loss of variation. Therefore; the efforts in the improvement of bread wheat are not as much fruitful as they should be.
The improvement in wheat production stands stagnant once again while the population is still increasing. Wheat genetic resources particularly wild relatives have broad genetic base and are important resources of beneficial traits. The present situation demands conservation and wise utilization of wild breeding programs for higher yield and other valuable traits.
Synthetic wheat
Plant breeders and geneticists have taken the initiative to search the valuable traits in the wild relatives and their use in the breeding programs. This quest has finally laid the foundation of synthetic wheat, a novel revolution in wheat.
Synthetic wheat is produced by a cross between T. turgidum L. (2n=4x=28, BBAA) and Aegilops tauschii (2n=2x=14, DD). T. turgidum has better agronomic type while Aegilops tauschii has more genetic diversity and has efficiency in incorporating alien genes into cultivated wheat.
A female T. turgidum is crossed with male Aegilops tauschii. This cross results into triploid F1 progeny. Then, colchicine is applied to the triploid F1 progeny to double the chromosome number. An allopolyploid hybrid of wheat is produced that is known as synthetic hexaploid wheat.
The chromosomes in such synthetic hexaploid wheat are completely homologous to that of cultivated hexaploid wheat and can recombine directly with it. This characteristic enables synthetic wheat to work as a bridge between cultivated wheat and its progenitors. The valuable traits can be introduced from progenitors to the cultivated wheat through that bridge.
In the beginning of 20th century, successful attempts were made to develop synthetic wheat during a study to determine progenitors of cultivated wheat. In 1946 E.S. McFadden and E.R. Sears developed the first synthetic wheat by using colchicine.
After a long period of studies on synthetic wheat production, plant breeders and geneticists succeeded to present first synthetic wheat based variety to the farmers for agricultural production during 1980s.
In 1980, International Maize and Wheat Improvement Center (CIMMYT) used the synthetic wheat in the breeding program with a desire to breed for resistance to Karnal bunt. Today, the number of synthetic wheat varieties developed by CIMMYT and other researchers has exceeded 1000.
Synthetic wheat plays role in yield Improvement
Synthetic wheat is an important tool to break the yield per unit area barrier. A Pakistani plant geneticist Abdul Mujeeb Kazi along with M. Van Ginkel at International maize and Wheat Improvement Center CIMMYT, Mexico are working on it. Their experiments clearly reports that when synthetic wheat cross with cultivated variety, it produced higher yield than its donor parent cultivation.
They developed two synthetic wheat varieties in 2004. They both had 20% to 35% higher yield than commercial varieties. In addition, synthetic wheat has the capability to store higher concentrations of both micro and macronutrients in than that of cultivated wheat. It possesses higher concentration of necessary elements like Fe, Mn, K, and P in grains.
It’s best example is Carmona. Carmona is a synthetic wheat derivative, first register by Spain in 2003. It has better grain quality and resistance to foliar diseases.
A goldmine for wheat improvement
Synthetic wheat is a goldmine for wheat improvement. It has valuable genetic variability for resistance to biotic and tolerance to abiotic stresses.
Rust is one of the most damaging universal diseases of wheat. It causes massive loss in wheat yield annually throughout the world. Synthetic wheat has potential genes for leaf rust and stripe rust.
Synthetic wheat showed resistance to numerous other diseases like, stem rust, tan spots, yellow leaf spot, Karnal bunt, powdery mildew, leaf blight, leaf blotch, glume blotch and spot blotch.
It also showed resistance to certain insect pests like Russian white aphid, Green bug, and Hessian fly. The resistance against biotic stresses reduces yield loss as well as helps cope the severe effects of climate change on wheat crop.
Synthetic wheat has significant tolerance to various abiotic stresses like heat, drought and salinity. The synthetic wheat derivatives of primary synthetics, when grown under rainfed conditions, showed up to 30 % increase in yield over local modern check varieties.
These synthetic varieties have thicker and deeper root systems that assist plants to take water from depths and help survive under water scarcity. Synthetic wheat cultivars have more genetic variability for salinity than modern wheat cultivars. They are also tolerant to heat stress at grain filling stage.
Combat against climate change
Climate change is increasing average world temperature and reducing water resources. These two factors together are making agricultural lands drier. Furthermore, agricultural land area is shrinking due to increased urbanization.
In contrast, the world population is increasing rapidly. The world requires more wheat to feed the increasing population. A recent estimate shows that, in 2050, world need 29% more wheat compared to the present wheat to feed the population. The statistics clearly defines that failure to fulfill the food demand of increasing population will inevitably lead to food wars.
In this context, the only solution to avert this situation is to increase yield per unit area. This can only achieve by developing varieties that have higher yield, better adaptation and more resistance to biotic and abiotic stresses.
Future prospects of synthetic wheat
Since Green Revolution Pakistan have the best wheat varieties than ever had. These varieties produce maximum possible yield. However, the maximum yield levels have become constant for the last decade. Fortunately, higher yields are still possible.
The prophecy of the Holy Quran says that a single wheat seed has the potential to produce hundreds of seeds. This target is far beyond the present-day wheat yield levels. In order to achieve this target, it is necessary to expand the narrow genetic base of wheat by borrowing the genes from its wild relatives.
Today, synthetic wheat appears to be the best, strongest and closest source for developing varieties with higher yield and better resistance to environmental stresses. For this reason, plant breeders must emphasize the production of synthetic wheat and its use in breeding programs to prevent starvation of children and to ensure world peace.
Good news is that, a group of scientists working at National Institute of Agricultural Botany (NIAB), Cambridge University has already succeeded to develop high yielding wheat variety, naming ‘Super Wheat’.
According to the scientists at NIAB, super wheat in its yield trials showed 30% higher yield than the existing varieties and confirmed resistance against various biotic and abiotic stresses in its preliminary tests. Globally ‘Super Wheat’ is regarding as a landmark in the synthetic wheat and will be the first commercial form of synthetic wheat. This upcoming super wheat will release in 2019.
This article is collectively authored by Mujahid Ali, Khadar Khan, and Hassan Raza. The authors are associated with department of Plant Breeding and Genetics at University of Agriculture, Faisalabad. The corresponding author can be reached at mujahid.ali2k17@gmail.com