A new indica rice germplasm with Arabidopsis-like life cycle and high-efficiency genetic transformation as a model system for functional genomics research

Functional genomics research on indica rice is often hindered by its long growth cycle and recalcitrance to genetic transformation. Therefore, there is an urgent need for Arabidopsis- like indica rice varieties that have a high efficiency in genetic transformation in order to facilitate functional genomics research. Here, we report the development of a new indica variety, named 6-23, which has a significantly short growth cycle and can be used as an indica model system. 6-23 is a recombinant inbred line created by crossing Chaling common wild rice with indica rice Guanglu'ai-4. The heading date of 6-23 is 45-55 days, which is about 30 days shorter than the model japonica rice Nipponbare (Nip). Additionally, 6-23 has more primary branches and grains per panicle compared to Nip. We further optimized the Agrobacterium- mediated genetic transformation system of 6-23, achieving a transformation efficiency of over 80%, equivalent to that of japonica rice. The callus regeneration efficiency of 6-23 exceeded 95%, which was superior to Nip. The highest genome editing efficiency mediated by CRISPR (clustered regularly interspaced short palindromic repeats) was similar to 71% under the 6-23 background, and the genomeedited plants were suitable for phenotypic analysis. Moreover, the construction of transgenic and genome-edited plants using 6-23 does not affect the heading date. Taken together, 6-23 can be used as an indica model system for functional genomics research.