Breeding for high water-use efficiency

Abstract

There is a pressing need to improve the water-use efficiency of rain-fed and irrigated crop production. Breeding crop varieties with higher water-use efficiency is seen as providing part of the solution. Three key processes can be exploited in breeding for high water-use efficiency: (i) moving more of the available water through the crop rather than it being wasted as evaporation from the soil surface or drainage beyond the root zone or being left behind in the root zone at harvest; (ii) acquiring more carbon (biomass) in exchange for the water transpired by the crop, i.e. improving crop transpiration efficiency; (iii) partitioning more of the achieved biomass into the harvested product. The relative importance of any one of these processes will vary depending on how water availability varies during the crop cycle. However, these three processes are not independent. Targeting specific traits to improve one process may have detrimental effects on the other two, but there may also be positive interactions. Progress in breeding for improved water-use efficiency of rain-fed wheat is reviewed to illustrate the nature of some of these interactions and to highlight opportunities that may be exploited in other crops as well as potential pitfalls. For C3 species, measuring carbon isotope discrimination provides a powerful means of improving water-use efficiency of leaf gas exchange, but experience has shown that improvements in leaf-level water-use efficiency may not always translate into higher crop water-use efficiency or yield. In fact, the reverse has frequently been observed. Reasons for this are explored in some detail. Crop simulation modelling can be used to assess the likely impact on water-use efficiency and yield of changing the expression of traits of interest. Results of such simulations indicate that greater progress may be achieved by pyramiding traits so that potential negative effects of individual traits are neutralized. DNA-based selection techniques may assist in such a strategy.

The mutual responses of higher plants to environment: Physiological and microbiological aspects

“…Plants live in soil-plant-atmosphere continuum (SPAC) environment, and they have to coordinate the mechanisms of diverse types to respond to the above changing environment at any time for sustainable survival [4][5][6][7][8][9][21][22][23][24][25][26][27][28][29][47][48][49][50][51][52][53][54][55][56][57][58][59]. Plant production realization is obtained eventually through physiological pathways at least at the level of individual and community [102][103][104][105][106][107][108][109]120,[130][131][132][133][134][135][136][137][138][139][140].…”

“…Plant production realization is obtained eventually through physiological pathways at least at the level of individual and community [102][103][104][105][106][107][108][109]120,[130][131][132][133][134][135][136][137][138][139][140]. One molecule or cell cannot produce any economic effect in field [22,23,77,78,117]. Under the condition of ensuring plant survival, plants can produce corresponding yield.…”

“…Water deficits in soil environment also influence solute transport (ion and nutrient uptake of plants) to larger extent, which effects on photosynthetic reactions in plant chloroplasts in many ways [117,120,131,135,[139][140][141][142][143][144][145][146][147]. This is the reason that ion homeostasis and redox state have been brought to attention [4][5][6][7][21][22][23][24][25][26][27][28][29][111][112][113][114][115][116][117][118][119]. The series of the above reactions and processes occurring at different soil-root biointerfaces is regulated and controlled by plant gene regulatory network system spatially and temporally on the basis of responding to plant developmental cues, through which plants can elegantly respond to the changing environment [8][9][10][11][12][13][14][15][16][17]…”

“…It is also a urgent need for human life that we should create crop plants that are able to confront successfully unfavorable natural conditions [7,10,11,[128][129][130][131][132][133][134]144]. The main aim in plant breeding is to obtain plants that combine higher yields, reliable yield stability, better quality and obvious characters resisting stresses (abiotic and biotic) over years and locations [15,16,22,36]. However, in addition to biotic stress factors, disturbances of extreme or even mild abiotic stress are supposed to account for a high amount of unachieved potential in plant production all over the globe [22,23,72,73,77,78].…”

“…The main aim in plant breeding is to obtain plants that combine higher yields, reliable yield stability, better quality and obvious characters resisting stresses (abiotic and biotic) over years and locations [15,16,22,36]. However, in addition to biotic stress factors, disturbances of extreme or even mild abiotic stress are supposed to account for a high amount of unachieved potential in plant production all over the globe [22,23,72,73,77,78]. Diverse forms of abiotic stresses may occur, including drought, cold and freezing, heat, salinity, nutrient deficiency, toxic heavy metals, oxidative stress as well as oxygen shortage, and mechanical stress [37,88,115].…”