Effects of ear shading on the anthocyanin contents and quality of kernels in various genotypes of maize.

This study aimed to investigate anthocyanin accumulation and the effects of shading on the quality and anthocyanin contents of kernels in various genotypes of maize (Zea mays L.). The ears of four differently-colored cultivars of maize, (Xixingheinuo NO1 [black], Zinuoxiang [purple], Xixingchinuo NO1 [red] and Yuxiangnuo [white]) were shaded after anthesis using opaque bags. Changes in grain colors of maizeseeds during development under shading treatment and the location of coloration were observed. Anthocyanin, total phenolic compounds, starch, soluble protein and sugar contents, as well as phenylalanine ammonialyase (PAL) activity, were also measured. Over 99% of the anthocyanin content in Xixingchinuo NO. 1 was found in its pericarp and seed coat. In Zinuoxiang and Xixingheinuo NO1, over99% of their anthocyanin contents were found in the aleurone layer. Shade treatment (The ears shaded after anthesis using opaque bags from anthesis until harvest) decreased the intensity of the kernels' apparent color. Shade treatment significantly reduced anthocyanin production during the early grain filling stage of growth, but the difference in percentage of reduction between the control and shade-treated plants decreased during development. In contrast, differences of total phenolic contents between the control and shade-treated plants were increased, except Yuxiangnuo, Shade treatment decreased anthocyanin and total phenolic contents by 68.6%, 68.8%, 60.0% 56.1% and 20.6%, 3.6%, 6.6%, 10.0%, respectively, in Yuxiangnuo, Xixingchinuo NO1, Zinuoxiang, and Xixingheinuo NO1 15 d post-anthesis(DPA). Further decreases to 9.7%, 15.8%, 31.7%, 37.0% and 8.3%, 12.6%, 13.7%, 20.4%, respectively, were observed in the same plants at 50 DPA. These findings show significant differences in anthocyanin and total phenolic syntheses in maize. Shade treatment decreased PAL activity, soluble sugar and starch contents but increased soluble protein contents compared with control kernels. The results of this study indicate that fresh ears could be picked at about 35 DPA, at which point anthocyanin contents would be at maximum levels. Dissimilar farina pollination, as well as good light in greceipt by plants, not shaded ears, and the high grain filling rate, could improve anthocyanin contents in maize.