Rice roadmap provides an alternative to the quest for “mega-varieties”

8 September, 2011 by (comments)

Boosting rice production to feed a rapidly growing world population requires an urgent, coordinated global effort, according to a group of leading rice scientists.

The scientists set out a roadmap for improving the “yield potential” of rice – the plant’s genetic capability to produce grain – during a special meeting of The Global Rice Science Partnership (GRiSP) at CIAT’s headquarters in Colombia.

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With global rice demand expected to rise by more than 25% by 2035, GRiSP brings together the world’s premier rice scientists and research institutions to help them share information, technology and expertise for the development more productive rice crops.

Acknowledging the “lost decades” of research aimed at producing high-yielding rice strains like those that triggered the Green Revolution of the 1960s and 1970s, Achim Dobermann, deputy director general for research at the International Rice Research Institute (IRRI), said: “The age of the ‘mega-varieties’ may be over,” and called for a new focus on work to achieve gradual, systematic genetic gains in yield potential.

All hands on deck…
Scientists at the GRiSP Yield Potential Workshop agreed that there is a need for more risky “blue-sky” research and greater emphasis on diverse rice improvement approaches on a global scale. These include hybrid rice development, for example, which has so far been applied with promising results – but only in particular rice-growing regions.

Scientists hope the new effort will deliver steady incremental gains in rice production, comparable to those achieved for maize in developing countries since the 1970s. This work will complement pioneering but uncertain research aimed at ramping up photosynthesis in rice, which, if successful, could deliver a quantum leap in yield potential.

In addition, the workshop identified several “safe-bet” rice breeding approaches, which fall into three categories.

One involves the creation of a more yield-efficient plant type through “pyramiding” of genes associated with plant traits that are known to be associated with higher yields, based on extensive knowledge of rice physiology. Such an approach was tried in the 1990s but fell short of expectations.

Scientists also aim to take advantage of more powerful tools from molecular biology and vast amounts of new information and technologies available from the fields of crop genomics and phenomics. Among other benefits, scientists will be better able to exploit genes from wild plants related to rice that control traits associated with higher grain yields.

To gain a better understanding of the combinations of traits most likely to raise yields, scientists will soon begin using simulation modeling for analysis of such traits in “virtual plants.”

Hybrid rice development, pioneered by Chinese scientists, has resulted in impressive yield increases of 15 to 20 percent. The Program at IRRI seeks to extend these gains to other Asian countries.

A third approach substitutes a breeding technique known as “recurrent selection” for the conventional “pedigree” approach to rice breeding. Commonly used for maize improvement, recurrent selection has made possible steady improvement in the yield potential of this crop.

About 20 years ago, rice scientists at CIAT and Brazilian Enterprise for Agricultural Research (EMBRAPA) working in collaboration with colleagues at CIRAD, began applying recurrent selection to rice breeding in South America, especially for the improvement of tolerance to specific stresses, such as soil infertility. Building on this experience, new rice populations will be developed for recurrent selection in Asia.

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“Assembling these different approaches into a concerted and coherent global rice breeding effort is a big step forward toward achieving the gains in yield potential that are essential for meeting increased demand in the coming decades,” continued Dobermann.

In his concluding remarks, CIAT’s Agrobiodiversity Research Area Director Joe Tohme, agreed: “We have a major challenge ahead of us; we cannot continue to repeat what we have done in the past. This is a unique time for the rice breeding community to embrace new tools and new collaboration in order to make major progress.”

…but mind the gap
Rice breeders are well aware that, in addition to raising the crop’s yield potential through a broad portfolio of genetic approaches, it is also necessary to narrow the gap between potential and actual yields under farmers’ conditions through better crop management. For this latter purpose, Latin America offers useful lessons. Its system of direct rice seeding in dry soil – which contrasts with Asia’s labor-intensive system of transplanting seedlings in flooded rice paddies – will likely spread in the latter region, as rapid urbanization makes rural labor ever more scarce and expensive.

Novel approaches for promoting improved crop and water management practices have made possible striking increases in farmers’ direct-seeded rice crops in South and Central America.

The GRiSP Yield Potential workshop was held at CIAT on the 22-25 August 2011.

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