Breeding and Cereal Yield Progress

Abstract

C ereals, dominated by wheat, rice, and maize, provide approximately 50% of human food calories directly and considerably more indirectly via feed grains (Tweeten and Thompson, 2008). Over the last 20 yr, a period chosen to best estimate current rates of progress without infl uence of earlier periods, the linear rates of yield change for the world (Fig. 1) Even if these relative rates could be maintained, various studies suggest they would not prevent real price rises for the three cereals, in the face of projected demand growth to 2050 (Tweeten and Thompson, 2008). Thus there is little doubt that the world needs to continue increasing cereal yields.In this paper we focus on factors determining current rates of yield progress in several key situations (or case studies) and consider Breeding and Cereal Yield Progress ABSTRACTThis paper reviews recent progress in wheat (Triticum aestivum L.), rice (Oryza sativa L.), and maize (Zea mays L.) yields resulting from substantial breeding efforts in mostly favorable environments and examines its physiological basis. Breeding and improved agronomy lift potential yield (PY), namely yield with the best variety and management in the absence of manageable abiotic and biotic stresses, and PY increase is a key component of progress in farm yield (FY), the other component being closure of the PY to FY gap. Changes in PY and FY are reviewed for several key production regions, namely the United Kingdom and the Yaqui Valley of Mexico for wheat, Japan and Central Luzon in the Philippines for rice, and Iowa and briefl y sub-Saharan Africa for maize. The PY growth rates have fallen and are currently generally no more than 1% per annum and usually much less. The trajectory of FY with time often closely parallels PY, but, especially in developing countries, there remain large yield gaps. In at least one instance (maize in Iowa) the gap between PY and FY appears to be closing rapidly. Current genetic progress is linked to increased biomass accumulation, and this will remain the way forward in the future given the limits to increased harvest index (HI). There is evidence that recent progress is related to increased photosynthesis (e.g., greater radiation use effi ciency (RUE) at the canopy level and/or maximum photosynthetic rate P max at saturating irradiance at the leaf level) before and around anthesis. There is no theoretical reason why this trend cannot continue, especially given the vast genetic resources already found within each crop species. However, it will not be easily or cheaply accomplished, so prospects for higher rates of potential yield growth appear to be limited, notwithstanding new molecular tools and claims to the contrary. Closing the yield gap, therefore, becomes more important. Many factors are involved, but breeding can also help farmers achieve this through, for example, improved host plant resistance.

The Roles of ATP Synthase and the Cytochrome b 6/f Complexes in Limiting Chloroplast Electron Transport and Determining Photosynthetic Capacity

“…It has been argued that a new green revolution is needed in world agriculture to increase crop yields for food security (Fischer and Edmeades, 2010). Increasing leaf photosynthetic capacity provides one attractive avenue to drive increases in crop yields (see Long et al, 2006;Peterhansel et al, 2008).…”

Perspectives for the Use of Quantitative Genetics in Breeding of Autogamous Plants

“…Strategies particular to the mode of reproduction are used in breeding these plants. Available information indicates that breeding of this type of plant has been successful in different regions of the world [2][3][4].…”

Does Morphological and Anatomical Plasticity during the Vegetative Stage Make Wheat More Tolerant of Water Deficit Stress Than Rice?

“…Rice, with a semiaquatic behavior, consumes about 30% of the total fresh water available for agricultural crops worldwide, which equates to a 2-to 3-fold higher consumption than other cereals such as wheat and maize (Zea mays; Peng et al, 2006). Despite a significantly lower water requirement, the potential yield of wheat in a favorable environment (9 tons ha 21 ) is comparable with the yield of fully flooded rice (9 tons ha 21 ) in the dry season at the International Rice Research Institute (IRRI; Fischer and Edmeades, 2010). Hence, rice records very low water productivity compared with wheat and other dryland cereals.…”