Rapid generation of a tomato male sterility system and its feasible application in hybrid seed production

Abstract

Male sterility enables reduced cost and high seed purity during hybrid seed production. However, progress toward its commercial applicationhas been slow in tomato due to the disadvantages of most natural male-sterile mutants. Here, we developed a practical method for e cient tomato hybrid seed production using a male sterile system with visible marker, which was rapidly generated by CRISPR/Cas9-mediated gene editing. Two closely linked genes, TM6 and DFR, which were reported to be candidates of ms15 (male sterile-15) and aw (anthocyanin without) locus respectively, were knocked out simultaneously in two elite tomato inbred lines. Mutagenesis of both genes generated green hypocotyl male-sterile (GHMS) lines, exhibiting male-sterility across different genetic backgrounds and environmental conditions and showing green hypocotyl due to defective anthocyanin accumulation, which serves as a reliable visible marker for selecting male-sterile plants at the seedling stage. We further proposed a strategy for multiplying the GHMS system and veri ed its high e ciency in stable male sterility propagation. Moreover, elite hybrid seeds were produced using GHMS system for potential side effects evaluation, and no adverse in uences were found on seed yield, seed quality as well as important agronomic traits. This study provides a practical approach for the rapid generation and feasible application of male sterility in tomato hybrid breeding. Key MessageA practical approach for the rapid generation and feasible application of green hypocotyl male-sterile (GHMS) tm6 dfr lines in tomato hybrid breeding was established.

Insights into the functional role of tomato TM6 as a transcriptional regulator of flower development

“…The ms15 mutant plants develop flowers with reduced and deformed anthers and exerted stigmas, traits that facilitate hand pollination. This is the ultimate usefulness of this kind of mutants for hybrid seed production in crop species like tomato [ 27 ]. Nevertheless, unlike what has been observed in the sus2 mutant, there have been no reported changes in petal morphology in ms15 mutant plants, suggesting that different domains of the TM6 protein are required to develop specific floral phenotypic traits.…”

Candidate Gene Identification and Transcriptome Analysis of Tomato male sterile-30 and Functional Marker Development for ms-30 and Its Alleles, ms-33, 7B-1, and stamenless-2

“…Based on these variations, three codominant markers—KASP marker MS30KASP, sequencing marker MS33SEQ, and InDel marker LeG-LO2-6/SL-2TE—were developed, facilitating rapid incorporation of these loci into tomato breeding. Additionally, CRISPR/Cas9-mediated targeted mutagenesis represents another approach to rapidly introduce male sterility into elite breeding lines [ 9 , 48 , 49 , 50 , 51 , 52 ]. The phenotypes of two TPI gene-edited mutants closely matched those of ms - 30 and its alleles, suggesting that gene editing of TPI could efficiently induce male sterility in elite lines, thereby reducing the costs associated with hybrid seed production.…”

Lipid and sugar metabolism play an essential role in pollen development and male sterility: a case analysis in Brassica napus

“…Moreover, several biotechnology‐based male‐sterility systems have been successfully developed in crops based on cloned GMS genes (Du et al 2020, Jiang et al 2021, Cheng et al 2023, Zhou et al 2023). CRISPR/Cas9‐mediated knockout of TM6 and DFR , two candidates of the ms15 locus ( male sterile‐15 ) and the aw locus ( anthocyanin without ), a male‐sterile line with visible green hypocotyl maker, were created for hybrid production in tomato (Zhou et al 2023). After mutation of a stamen‐specific gene SlSTR1 , a new biotechnology‐based male‐sterility system was developed in tomato (Du et al 2020).…”

“…These GMS genes related to lipid and sugar metabolism are predominantly from Arabidopsis and rice, while their orthologs tend to have similar biological functions in the other species (Dong et al 2016, Zhang et al 2016, Xu et al 2019b, Stamboulian et al 2020, Escalante et al 2022, Schultz et al 2023, suggesting that some metabolic steps of male reproductive development have been conserved throughout plant evolution. The conserved properties have demonstrated the great potential for the application of genes related to lipid metabolism in plant breeding and heterosis utilization, while the mechanism by which functional genes may differ between different species remains to be further elucidated.…”