Assessment of cultivated and wild, weedy rice lines to concurrent changes in CO2 concentration and air temperature: Determining traits for enhanced seed yield with increasing atmospheric CO2

Authors: Ziska, Lewis; Tomecek, Martha; Gealy, David

Submitted to: Functional Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/1/2013
Publication Date: 1/1/2014
Citation: Ziska, L.H., Tomecek, M.B., Gealy, D.R. 2014. Assessment of cultivated and wild, weedy rice lines to concurrent changes in CO2 concentration and air temperature: Determining traits for enhanced seed yield with increasing atmospheric CO2. Functional Plant Biology. 41:236-243.

Interpretive Summary: Although carbon dioxide (CO2) is a greenhouse or warming gas, it is also the source of carbon for plant growth. Consequently its increase in the atmosphere represents an opportunity to exploit CO2 or utilize CO2 more effectively to increase seed yields. One means to exploit CO2 is to screen crop varieties so as to determine which one is best able to convert additional CO2 into more seed yield. We did this for rice, a primary source of calories globally, using four different lines, including a wild, or weedy line, "StgS". We found that while all lines responded with more seed yield as CO2 increased; as temperature increased, the stimulation of seed yield by CO2 declined. The exception however was the weedy line, "StgS" which increased seed yields even at day/night temperatures up to 33/25oC. In examining how this weedy rice line was able to do this, we discovered a good correlation between the ability of varieties to develop stems (tillers) early on, and the response of seed yield to CO2/temperature. Our results suggest that including novel genes from weedy lines could help in adapting crops like rice to future climate change; and that early differences in tiller formation may be one way to determine which lines are better able to exploit, or convert CO2 into seed yield. This information will be of interest to plant breeders, plant scientists and those interested in climate change and food security.

Technical Abstract: Although a number of studies have examined intra-specific variability in growth and yield to projected atmospheric CO2 concentration, [CO2], none have compared the relative responses of cultivated and wild, weedy crop lines. We quantified the growth and seed yield response for three cultivated ("4484", "Clearfield 161", "M204") and one wild (red) rice line ("StgS"), grown at ambient and +200 µmol mol-1 [CO2] at three day/night temperatures (29/21, 31/23, 33/25oC). Averaged among all cultivars, [CO2] did increase biomass and seed yield; conversely, increasing air temperature reduced the [CO2] response of both parameters. Among the cultivated and weedy rice tested, "4484" and "StgS" showed significant increases in above-ground biomass and seed yield with elevated [CO2] at 29/21oC; however, only "StgS", the weedy rice line, demonstrated a significant increase with [CO2] at all growth temperatures. A regression analysis for this line indicated that the relative increase in seed yield with [CO2] and air temperature was positively associated with panicle and tiller number, and negatively correlated with the percentage of undeveloped seed. An analysis of all lines indicated that the ratio of tiller production between CO2 treatments at 30 days after sowing (DAS) was a significant predictor of seed yield response to increasing [CO2] for all temperatures. These results suggest that: (a) Inclusion of wild lines may broaden genotypic or phenotypic variation and assist in selection to temperature/[CO2]; and, (b) Early differences in tiller formation may be an effective means to facilitate screening for CO2 sensitive rice genotypes.