Effects of tall alleles SD1-in and SD1-ja to the dwarfing allele sd1-d originating from 'Dee-geo-woo-gen' on yield and related traits on the genetic background of indica IR36 in rice.

sd1-d originating from 'Dee-geo-woo-gen' has been utilized to develop short-culmed indica varieties adaptable to higher fertilizer-application. Its tall alleles SD1-in and SD1-ja are harbored in indica and japonica subspecies, respectively. The sd1-d of indica IR36 was substituted with SD1-in or SD1-ja by recurrent backcrossing with IR36, and two tall isogenic lines ("5867-36" and "Koshi-36") were developed. IR36, 5867-36 and Koshi-36 were grown in a paddy field in three years, and yield and related traits were measured, the effects of SD1-in and SD1-ja on yielding ability and related characteristics were examined on the genetic background of IR 36. SD1-in decreased panicle number per m2 but increased spikelet number per panicle, ripened-grain percentage and 1000-grain weight, compared with sd1-d, resulting in the increase of yield. The increase of 1000-grain weight by SD1-in, caused by the increases of length, width and thickness of grain, was due to the increases of the length and width of lemma. SD1-ja did not significantly affect yield, mainly because the decrease of panicle number per m2 was compensated by the enlarged 1000-grain weight owing to the increase of lemma length. Serious lodging was observed in long-culmed 5867-36, suggesting that sd1-d is indispensable for indica breeding programs.

Ozone changes the linear relationship between photosynthesis and stomatal conductance and decreases water use efficiency in rice.

Ozone is an important air pollutant that affects growth, transpiration, and water use efficiency (WUE) in plants. Integrated models of photosynthesis (An) and stomatal conductance (Gs) (An-Gs) are useful tools to consistently assess the impacts of ozone on plant growth, transpiration, and WUE. However, there is no information on how to incorporate the influence of ozone into An-Gs integrated models for crops. We focused on the Ball-Woodrow-Berry (BWB) relationship, which is a key equation in An-Gs integrated models, and aimed to address the following questions: (i) how does ozone change the BWB relationship for crops?; (ii) are there any difference in the changes in the BWB relationship among cultivars?, and (iii) how do the changes in the BWB relationship increase or decrease WUE for crops? We grew four rice cultivars in a field under ambient or Free-Air Concentration Enrichment (FACE) of ozone in China and measured An and Gs using a portable photosynthesis analyzer. We simulated WUE in individual leaves during the ripening period under different BWB relationships. The results showed that ozone significantly changed the BWB relationship only for the most sensitive cultivar, which showed an increase in the intercept of the BWB relationship under FACE conditions. These results imply that changes in the BWB relationship are related to the ozone sensitivity of the cultivar. Simulations of an An-Gs integrated model showed that increases in the intercept of the BWB relationship from 0.01 to 0.1 mol(H2O) m-2 s-1 indicated decreases in WUE by 22%. Since a reduction in WUE indicates increases in water demand per unit of crop growth, air pollution from ozone could be a critical issue in regions where agricultural water is limited, such as in rainfed paddy fields.

A stomatal ozone flux-response relationship to assess ozone-induced yield loss of winter wheat in subtropical China.

Stomatal ozone flux and flux-response relationships were derived for winter wheat (Triticum aestivum L.) grown under fully open-air ozone fumigation. A stomatal conductance (g(sto)) model developed for wheat in Europe was re-parameterized. Compared to European model parameterizations, the main changes were that the VPD and radiation response functions were made less and more restrictive, respectively, and that the temperature function was omitted. The re-parameterized g(sto) model performed well with an r(2) value of 0.76. The slope and intercept of the regression between observed and predicted g(sto) were not significantly different from 1 to 0, respectively. An ozone uptake threshold of 12 nmol m(-2) s(-1) was judged most reasonable for the wheat flux-response relationship in subtropical China. Judging from both flux- and concentration-based relationships, the cultivars investigated seem to be more sensitive to ozone than European cultivars. The new flux-response relationship can be applied to ozone risk assessment in subtropical regions.