Breeding of CMS maintainer lines through anther culture assisted by high-resolution melting-based markers

The integrated use of molecular marker-assisted selection (MAS) and anther culture has potential to significantly increase efficiency in plant breeding;however, reports on this kind of practical use are very limited. In the present study, we report the development of cytoplasmic male sterile (CMS) maintainers with aroma, disease resistance and red-brown hulls, as an example of integration of MAS and anther culture in rice breeding. A high-resolution melting (HRM)-based functional molecular marker was developed for the red-brown hull trait caused by a unique mutation (rbh1) in OsCAD2. Functional molecular markers for genes of rice blast resistance (Pi2), aroma (fgr) and red-brown hull (rbh1) were used for precise genotyping of individual plants in the BC1 and BC2F2 populations derived from a cross between CMS maintainers Huaxiang B (pi2–/rbh1–/fgr–) and Rong 3B (Pi2+/RBH1+/Fgr+). A total of 89 doubled haploid (DH) lines were generated from selected BC2F2 plants (Pi2+/rbh1–/fgr–) by anther culture. Seven DH lines were subsequently selected as the potential new CMS maintainers based on their overall performance and high resistance to blast. Our study demonstrated that integration of MAS and anther culture significantly accelerated the development of CMS maintainers with multiple stacked genes.

The CRISPR/Cas revolution continues: From efficient gene editing for crop breeding to plant synthetic biology

Since the discovery that nucleases of the bacterial CRISPR(clustered regularly interspaced palindromic repeat)-associated(Cas) system can be used as easily programmable tools for genome engineering,their application massively transformed different areas of plant biology. In this review, we assess the current state of their use for crop breeding to incorporate attractive new agronomical traits into specific cultivars of various crop plants. This can be achieved by the use of Cas9/12 nucleases for double-strand break induction,resulting in mutations by non-homologous recombinatr e-tion. Strategies for performing such experiments à from Rthe design of guide RNA to the use of different transformation technologies à are evaluated. Furtherweive-more, we sum up recent developments regarding the use of nuclease-deficient Cas9/12 proteins, as DNAbinding moieties for targeting different kinds of enzyme activities to specific sites within the genome. Progress in base deamination, transcriptional induction and transcriptional repression, as well as in imaging in plants, is also discussed. As different Cas9/12 enzymes are at hand, the simultaneous application of various enzyme activities, to multiple genomic sites, is now in reach to redirect plant metabolism in a multifunctional manner and pave the way for a new level of plant synthetic biology.

ROLE OF NITROGEN SENSING AND ITS INTEGRATIVE SIGNALING PATHWAYS IN SHAPING ROOT SYSTEM ARCHITECTURE

The Green Revolution of the 1960s boosted crop yields in part through widespread production of semidwarf plant cultivars and extensive use of mineral fertilizers.The beneficial semidwarfism of cereal Green Revolution cultivars is due to the accumulation of plant growth-repressing DELLA proteins,which increases lodging resistance but requires a high-nitrogen fertilizer to obtain high yield.Given that environmentally degrading fertilizer use underpins current worldwide crop production,future agricultural sustainability needs a sustainable Green Revolution through reducing N fertilizer use while boosting grain yield above what is currently achievable.Despite a great deal of research efforts,only a few genes have been demonstrated to improve N-use efficiency in crops.The molecular mechanisms underlying the coordination between plant growth and N metabolism is still not fully understood,thus preventing significant improvement.Recent advances of how plants sense,capture and respond to varying N supply in model plants have shed light on how to improve sustainable productivity in agriculture.This review focuses on the current understanding of root developmental and metabolic adaptations to N availability,and discuss the potential approaches to improve N-use efficiency in high-yielding cereal crops.