The Future Way for Wheat  

D. Sun1,2 , X. He2
1. College of Agronomy, Northwest A&F University, Yangling 712100, China
2. CIMMYT (International Maize and Wheat Improvement Center), Apdo., Postal 6-641, 06600 Mexico, D.F., Mexico
Author    Correspondence author
Molecular Plant Breeding, 2014, Vol. 5, No. 15   doi: 10.5376/mpb.2014.05.0015
Received: 25 Oct., 2014    Accepted: 14 Nov., 2014    Published: 30 Dec., 2014
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Sun and He, The Future Way for Wheat, Molecular Plant Breeding, 2014, Vol.5, No. 15 1-3 (doi: 10.5376/mpb.2014.05.0015)

Abstract

The cultivated wheat,originated from Fertile Crescent,contributed to the emergence of the Ancient Egypt and Babylon’s culture. This process also promoted and expanded global civilizations. Today, the progress of wheat improvement has slowed down since last century’s “Green Evolution”. The patterns of genetic improvement, “Recombination plus Selection (R&S)”, have been used fullest such that the potential has nearly come to an ultimate. Today’s wheat is bearing extremely large "Encumbrance" of genetic regulation and plant-types development in the reproductive process. It is these "Encumbrance" which take the responsibility for wheat to survive and reproduce and avoid extinction in adversity. But for most environments, the burden is clearly superfluous. For this reason, different from the routine ways, “R&S” and “Genetically Modified” in wheat improvement, this essay propose a new idea: decreasing the “Sluggishness or Encumbrance” of the wheat development, increasing the smoothness and efficiency of growth and development.

Keywords
Wheat; Genetic improvement; New pattern

Crop’s cultivation is indispensable to humans as well as the development of human civilizations (Dorian Q. Fuller, 2011). The cultivated wheat derived from Fertile Crescent, and it contributes to the emergence of the Ancient Egypt and Babylon’s culture, and the process promoted and expanded global civilizations, too. Today, the wheat (Triticum aestivum) has become a special species, whose survival and reproduction depends entirely on the farming behavior of humanity. The wheat and human indeed share weal and woe with each other, and solidarity, and interdependence.

Over a century, geneticists and breeders have done numerous fruitful researches to improve wheat genotypes, and to develop characters of wheat more useful to humans, even in a “malformation” way. Up to now, scientists have explored and developed various wheat varieties, using conventional crosses, wide crosses with the association of cytological techniques and the molecular techniques, and screened almost all possible genetic combinations in the levels of genome, chromosome and DNA. By this, scientists have screened out a large number of excellent genotypes (T. Ryan Gregory, 2009). Meanwhile agronomists have also been enhancing the ways of cultivation, improving the efficiency of resource utilization, and decreasing the damages. But, even so, their concerted effort could just only meet the basic even the minimum food demands of the huge population (Petra Stamm et al.,2011).
The progress of wheat production improvement has slowed down since last century’s “Green Evolution”. The patterns of genetic improvement, “Recombination plus Selection (R&S)”, have been used fullest such that the potential has nearly come to an ultimate. The population will continue to grow in the next decades, so the increasing demand for wheat will be faster than the speed of today's wheat crop genetic improvement. In this scenario, where is the future of the wheat? Perhaps the suitable and optimum genes net for humanneed have achieved fromthe utilization of excellent resources both in and between Triticum species, promoting the fully exchange of elite genes, following by the multi-environmental phenotypes screening. Thewheat genome has been rebuilt and the best genotypes have almost been obtained (Rodomiro Ortiz et al., 2008; M. L. Warburton et al.,2006). In the future the challenge is how to increase wheat yield potential, how much could the pattern of “R&S” improve? And how long will the pattern sustain? The answers are not optimistic.
For this reason, different from the routine ways, “R&S” and “Genetically Modified” in crop improvement, this essay proposes an idea of genetic improvement: decreasing the “Sluggishness or Encumbrance” of the wheat development, increasing the smoothness and efficiency of growth development by “Remove impediment and release energy”.
To survive adversity and pathogens full of this planet, countless wheat varieties and their ancestors perished in the past millions of years. Today, wheat has obtained strong survival skills and reproductive abilities, and has also evolved stress resistance and reproductive guarantee capability, which is the basis for all species to survive (M.T. Assad et al., 2002). In the process of wheat evolution, the genome has enriched a lot of "Genetic Encumbrance". This " Encumbrance " is good for survival and adaptability and but not conducive to obtain high yield.
So, today’s wheat is bearing extremely large "Encumbrance" of genetic regulation and plant-types development in the reproductive process. However it is these "Encumbrance" which takes the responsibility for wheat to survive and reproduce and avoid extinction in adversity (For most environments, the burden is clearly superfluous). The wheat plant takes a lot of energy to carry on with these "white elephants". In some sense, the process of wheat improvement was one somewhat to reduce this burden intentionally or unintentionally, in the past century. With the development of the future biosciences, breeder could scientifically, systematically select and remove (sometimes to add) the superfluous burdens. Based on this concept, the stage approaches for improving wheat yield potential be put forward.
1 The next two decades
In essence, the role of Vernalization is fetter growth, and so do Dwarf and Photoperiod genes. These genes weaken growth vitality. Focus will be put on optimizing physiogenesis, eliminating the negative effects of wheat’s core genes net such as Dwarf, Vernalization and Photoperiod etc., which control the growth and development of wheat. For wheat improvement, the following work is very important: eliminating the inhibitive effects of unnecessary adaptive-related genes according to the different ecological conditions; increasing wheat's biomass accumulation; improving the transport efficiency of assimilates to grain and thus improving the harvest index. Take China’s core wheat area as an example: in the past 30 years, the Vernalization and Photoperiod Sensibility of the main varieties have decreased to less than medium level and thus the yield potential has got improved to some degree (Y. Zhou et al., 2007; Wei Wu et al., 2014). But the semiwinterness must be retain to prevent wheat from developing too fast before winter and to ensure safety from the cold of winter.The moderate photoperiod sensitivity should be retained too, so that the varieties do not develop too fast in early spring in order to avoid the cold spell.
2 Middle of this century
According to local ecological conditions the med-term plans can be divided into two aspects:
2.1 Wheat marginal adapt area
Among the closely related species of wheat, Secale has a growthand stress tolerance advantages which other Triticum resources cannot match (Hugh Wallwork, 1989). Utilizing the strong living ability and hard resistance of Secale and Triticale (add the necessary developmental "Encumbrance" if necessary), scientists can breed eurytopicity varieties which are sturdy, resistant, high-yielding. CIMMYT is doing research in this area (Figure 1). Also, according to the environmental conditions and the harvested organs, the production efficiency of "annual" and "perennial" habits should also be considered. So, scientists can regulate the wheat or triticale "regeneration" expression networks to create more appropriate and more efficient new varieties. The varieties can improve the production capacity of wheat in less adaptive area and expand growing region by increasing stress resistance.


Figure 1 Triticale and Wheat plots in CIMMYT. From web: http://www.cimmyt.org/

2.2
Wheat core area
The huge wheat genome (17 Gb) from wheat polyploidization provides complicated genetic regulatory networks for its growth and development of each developmental stage (Junhua H. Peng et al., 2011). This huge genome makes wheat own many superfluous traits as following: the physiological characters controlled by periodic development suppressor genes in Vernalization and Photoperiodic reaction; the agronomic traits of forming more tillers and more eustipes and leafiness; the reproductive properties of redundant florets and adequately grain protection. So, wheat has been given the capability of surviving in adversities and the capability of guaranteeing reproduction. However, many traits are non-required and energy-consuming under modern cultivation. With productivity level increasing, the future facility agriculture will be in rapid development. Accommodating future technology in facility agriculture (facility agriculture can largely shield adversity), using future research achievements of biosciences, wheat breeders and geneticists can make joint efforts to remove or reduce the many redundant traits and retain only those necessary genes networks for kernels formation and development. The great breeder should breed innovative varieties with short life spans, simplicity characters, high resource utilization efficiency, so as to realize production improvement by leaps and bounds. In this regard, the domestication and improvement of sunflower (Helianthus annuus) is a good example (Bruce D. Smith, 2014).
3 Century outlook
By the end of the century, if humans have solved the energy crisis and created a sustainable, green and safe, non-bio-energy-oriented energy way, food security pressure will be reduced. At that time, using the sophisticated biosciences and technology, new crops could easily be created. New wheat (supposing you can still call it wheat) containing excellent traits from various plants with high production efficiency could be one of the main crops that covered one-third land area on this planet.
In the future, breeders and geneticists will face many extremely complex biological problems. Crop improvement research requires more than just a practical project; it needs more adventurous, innovative and original thoughts. These thoughts will probably bring entirely new theory or technique, which will greatly accelerate the pace of crop improvement.
Acknowledgments
This work was supported by grants from China (2014CB138100, 2012AA101105, and 2012DFA32290) and the National Natural Science Foundation of China (31071408).
References and Notes
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http://dx.doi.org/10.1007/s00334-013-0393-3
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Hugh Wallwork, 1989, Screening for resistance to take-all in wheat, triticale and wheat-triticale hybrid lines, Euphytica, 40: 103-109
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Y. Zhou, H. Z. Zhu, S. B. Cai, Z. H. He, X. K. Zhang, X. C. Xia, and G. S. Zhang, 2007, Genetic improvement of grain yield and associated traits in the southern China winter wheat region: 1949 to 2000, Euphytica, 157: 465-473
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