Utilizing wild species to improve cultivated rice for yield, pest resistance, and response to climate change

Background/Question/Methods

Over 158 million hectares of rice are grown in the world providing a staple food for more than half the world’s population. Although there are several species of Oryza, essentially all cultivated rice is derived from O. sativa which can be genomically differentiated into five sub-populations. There are some 150,000 rice accessions in public gene banks that have been collected from over 100 countries and demonstrate the tremendous genetic diversity within this species that can be used by breeders to develop new cultivars that can be successfully grown under a wide array of environmental conditions. Red rice is a weed commonly found in rice production fields and is difficult to control because it is genetically similar to cultivated rice and there are no herbicides that can be used selectively for its control. In addition, weedy red rice possesses seed shattering and seed dormancy traits that allow it to persist in infested fields for years. Research was conducted to determine if red rice biotypes and cultivated rice would respond differently to elevated levels of CO₂ that are predicted to occur with climate change.

Results/Conclusions

It was determined that the red rice biotypes had greater physiological plasticity and were able to produce greater plant biomass and leaf area as compared to the cultivars. Initial results from a subsequent study evaluating the ability of red rice and herbicide resistant rice to intercross have shown that this occurs with a higher frequency under elevated CO₂. These findings suggest that under climate change scenarios, red rice may become more difficult to control in rice production fields and there may be greater risk for gene escape into feral weed populations. However, these results also indicate that weedy relatives of rice may possess desirable genes that can be used to develop new rice cultivars that respond positively to climate change. O. rufipogon is a wild weedy progenitor of cultivated rice and is known to possess novel genes for disease and insect resistance. We have demonstrated that such agronomically inferior species can also be used to increase rice yields by over 20%. We are in the process of developing genetic stocks derived from crosses of O. sativa with O. rufipogon to identify novel gene combinations that will benefit breeding efforts to mitigate the negative effects of climate change and help sustain global rice production.