Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/19/2015
Publication Date: 11/1/2015
Citation: Bryant, R.J., Yeater, K.M., Mcclung, A.M. 2015. Effect of nitrogen rate and the environment on physicochemical properties of selected high amylose rice cultivars. Cereal Chemistry. 92(6):604-610. doi.org/10.1094/CCHEM-02-15-0035-R.
Interpretive Summary: Rice cultivars that maintain their grain integrity after processing are preferred by the parboiling and canning industries. The best performing cultivars are known to have high grain amylose content and a unique starch paste viscosity curve when the rice is cooked. Genetic markers have been found that are linked to genes that control amylose content, starch paste viscosity curves, and starch gelatinization temperature and have been effectively used by rice breeders through marker assisted selection to distinguish rice cultivars that possess the desired parameters required by the processing industry. This study evaluated the processing characteristics of nine rice cultivars with high amylose content (>23 percent) that were grown in three environments and using three nitrogen fertility levels. In general, environment and fertility levels had an impact on the grain protein content, starch pasting viscosities, and starch gelatinization temperature, but the cultivars performed consistently across the different production environments. The results of this study demonstrated that although these high amylose cultivars had consistent ranking across environments and nitrogen fertility regimes, there were differences in rice processing quality traits that are not apparent using the current genetic markers.
Technical Abstract: Genetic marker haplotypes for the Waxy and alk genes are associated with amylose content and gelatinization temperature, respectively, and are used by breeders to develop rice cultivars that have physicochemical properties desired by the parboiling and canning industries. Cultivars that provide consistent processing quality across diverse production environments are important to the industry. This study determined if measures of rice processing quality differed among cultivars, fertility treatments, and production environments. Nine cultivars having high amylose content (>23.0 percent) but with different Waxy and alk haplotypes were evaluated in three environments and using three nitrogen fertility levels. Although environment and fertility levels significantly (p<0.05) impacted protein content, peak, trough and final paste viscosities, and gelatinization temperatures, cultivars performed consistently across production environments. Differences were observed among cultivars in paste viscosity measures and gelatinization temperatures that corresponded with their Waxy and alk haplotypes. However, discriminate analysis revealed sub-groupings within the same Waxy and alk haplotypes that were primarily differentiated by trough paste viscosity. The results of this study demonstrated that although these cultivars with high amylose content had consistent ranking across environments and nitrogen fertility regimes, there were differences in rice processing quality traits that are not apparent from their Waxy and alk haplotypes. Key Words: Rice, grain quality, high amylose rice, rice processing quality, parboiling, canning.