Innovation and development of the third-generation hybrid rice technology

The breeding and large-scale application of hybrid rice contribute significantly to the food supply worldwide.Currently,hybrid seed production uses cytoplasmic male sterile(CMS)lines or photoperiod/thermo-sensitive genic male sterile(PTGMS)lines as female parent.Despite huge successes,both systems have intrinsic problems.CMS systems are mainly restricted by the narrow restorer resources that make it difficult to breed superior hybrids,while PTGMS systems are limited by conditional sterility of the male sterile lines that makes the propagation of both PTGMS seeds and hybrid seeds vulnerable to unpredictable climate changes.Recessive nuclear male sterile(NMS)lines insensitive to environmental conditions are widely distributed and are ideal for hybrid rice breeding and production,but the lack of effective ways to propagate the pure NMS lines in a large scale renders it impossible to use them for hybrid rice production.The development of"the third-generation hybrid rice technology"enables efficient propagation of the pure NMS lines in commercial scale.This paper discusses the establishment of"the thirdgeneration hybrid rice technology"and further innovations.This new technology breaks the limitations of CMS and PTGMS systems and will bring a big leap forward in hybrid rice production.

Gm Ms1 encodes a kinesin-like protein essential for male fertility in soybean(Glycine max L.)

The application of heterosis is a promising approach for greatly increasing yield in soybean(Glycine max L.). Nuclear male sterility is essential for hybrid seed production and the utilization of heterosis. Here we report the cloning of the gene underlying the soybean male-sterile mutant ms-1,which has been widely used for recurrent selection in soybean breeding programs. We initially delimited the ms1 locus to a 16.15 kb region on chromosome13, based on SLAF_BSA sequencing followed by genotyping of an F_(2) population segregating for the locus. Compared with the same region in fertile plants, the mutant region lacks a sequence of approximately 38.7 kb containing five protein-coding genes, including an ortholog of the kinesin-like protein gene NACK2, named Gm Ms1. The Gm Ms1 knockout plants generated via CRISPR/Casmediated gene editing displayed a complete malesterile phenotype. Metabolic profiling showed that fertile anthers accumulated starch and sucrose normally, whereas sterile anthers had higher anthocyanin levels and lower flavonoid levels and lower antioxidant enzyme activities. These results provide insights into the molecular mechanisms governing male sterility and demonstrate that Gm Ms1 could be used to create male-sterile lines through targeted mutagenesis. These findings pave the way for designing seed production technology and an intelligent male-sterile line system to utilize heterosis in soybean.