Improving rice appearance quality through GS9 gene knockout

Indica and japonica rice differ in several quality and yield-related traits, including grain shape.

Grain shape and chalkiness are often correlated—grain width, in particular, is an important factor that influences grain filling. Wider grain is often accompanied by higher chalkiness, whereas slender grains can optimize grain-filling pathways, hence reducing the chalkiness without yield loss.

To address these issues, a team of researchers from China explored the breeding value of gs9 knockout alleles in different rice backgrounds and planting densities. Their findings were recently published in the Journal of Integrative Agriculture.

“Conventional modern japonica rice in China usually has short, round grains, which result in high yields but also have high chalkiness,” says corresponding author Qiaoquan Liu, a professor at Yangzhou University, China. “We aimed to modify grain shape by using the rare gs9 allele to reduce this undesirable chalkiness.”

“We confirmed that most currently grown japonica rice cultivars show short, wide grains and share the same allelic combination of the major grain size genes,” adds co-corresponding author Dongsheng Zhao, a professor at the same university. “Introducing the CRISPR/Cas9-generated knockout allele gs9^KO improved grain shape and reduced chalkiness across all tested japonica cultivars, without affecting yield-related traits.”

Furthermore, although plants carrying the gs9^KO allele showed a slight increase in leaf angle, this change did not influence final yield per plant under varying planting densities.

Overall, the study demonstrates that gs9^KO exerts a broadly beneficial effect on grain appearance improvement. The targeted knockout of the GS9 gene hence provides a molecular breeding strategy for improving grain shape and chalkiness in most japonica rice cultivars.

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Contact the author: 

Correspondence Dongsheng Zhao, E-mail: dszhao@yzu.edu.cn;

Qiaoquan Liu, E-mail: qqliu@yzu.edu.cn

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