Prognosis for genetic improvement of yield potential and water-limited yield of major grain crops

A.J. HALL; RICHARDS,R.A.

FIELD CROPS RESEARCH

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2013 vol. 143 p. 18 - 33

0378-4290

a b s t r a c tGenetic improvement of crop yields under potential (Yp) and water scarce conditions (Yw) will be animportant avenue to improved food security over the next four decades, at the end of which projecteddemand for food, feed and biofuel feedstock is expected to level out. Current measured relative rates ofimprovement in Yp and Yw for the three main cereal crops (maize, wheat and rice) in many croppingsystems in the world are mostly well below the 1.16–1.31% y−1 rates required to meet projected demandfor cereals in 2050. These relative rates can be expected to fall further if the current absolute rates of yieldimprovement continue unchanged and/or the current indications of stagnation in yield improvementfor some crops in some regions of the world become widespread. This review assesses the availableevidence for unexploited opportunities for enhancing current rates of genetic improvement for Yp andYw, and examines some substantive proposals for achieving the same end through genetic engineeringof photosynthesis, above-ground ideotype design, and improvement of root capacity for water uptake.Because time is of the essence, special attention is paid to the time scales required to progress potentiallyuseful traits through to proof of concept under field conditions, from there to farmer-ready cultivars,and for widespread adoption by farmers of the improved cultivars. The requirements of breeders forinclusion of potentially important traits into the conventional breeding process are outlined and the valueof molecular breeding tools as aids to genetic improvement of simple and complex traits is considered.Intellectual property and regulatory requirements are taken as additional potential drags on the rates ofadoption into the breeding process of useful traits and/or to the free flow of information between researchteams. Main conclusions are: (a) there are some unexploited opportunities to improve Yp or Yw in somecrops and/or cropping systems; (b) exploitation of these opportunities could be hastened by increasingfunding for focussed research and by identifying and eliminating or reducing drags at various stages ofthe idea to farmer-ready cultivar chain; (c) the time-scales required for major improvements in yieldin farmer-ready cultivars through genetic engineering or ideotype realisation are likely to be measuredin decades rather than years; (d) current and expected future relative rates of progress in Yp and Yware a matter of real concern and are insufficient to meet projected demand for cereals by 2050. Possiblestep changes in Yp or Yw powered by genetic improvements such as exploitation of hybrid vigour inrice or hypothetical successes in the genetic engineering of photosynthesis are unlikely to change thisoutlook. The pessimistic assessments embodied in the last two conclusions should not obscure the factthat without continued investment in the search for sources of genetic improvement and developmentof aids to breeding, the unmet demands for cereals in 2050 will be even greater.© 2012 Elsevier