Male sterility is a valuable trait for hybrid seed production in tomato (Solanum lycopersicum). The mutants male sterile-30 (ms-30) and ms-33 of tomato exhibit twisted stamens, exposed stigmas, and complete male sterility, thus holding potential for application in hybrid seed production. In this study, the ms-30 and ms-33 loci were fine-mapped to 53.3 kb and 111.2 kb intervals, respectively. Tomato PISTILLATA (TPI, syn. SlGLO2), a B-class MADS-box transcription factor gene, was identified as the most likely candidate gene for both loci. TPI is also the candidate gene of tomato male sterile mutant 7B-1 and sl-2. Allelism tests revealed that ms-30, ms-33, 7B-1, and sl-2 were allelic. Sequencing analysis showed sequence alterations in the TPI gene in all these mutants, with ms-30 exhibiting a transversion (G to T) that resulted in a missense mutation (S to I); ms-33 showing a transition (A to T) that led to alternative splicing, resulting in a loss of 46 amino acids in protein; and 7B-1 and sl-2 mutants showing the insertion of an approximately 4.8 kb retrotransposon. On the basis of these sequence alterations, a Kompetitive Allele Specific PCR marker, a sequencing marker, and an Insertion/Deletion marker were developed. Phenotypic analysis of the TPI gene-edited mutants and allelism tests indicated that the gene TPI is responsible for ms-30 and its alleles. Transcriptome analysis of ms-30 and quantitative RT-PCR revealed some differentially expressed genes associated with stamen and carpel development. These findings will aid in the marker-assisted selection for ms-30 and its alleles in tomato breeding and support the functional analysis of the TPI gene.

Late blight is a destructive disease affecting tomato production. The identification and characterization of resistance (R) genes are critical for the breeding of late blight-resistant cultivars. The incompletely dominant gene Ph-2 confers resistance against the race T₁ of Phytophthora infestans in tomatoes. Herein, we identified Solyc10g085460 (RGA1) as a candidate gene for Ph-2 through the analysis of sequences and post-inoculation expression levels of genes located within the fine mapping interval. The RGA1 was subsequently validated to be a Ph-2 gene through targeted knockout and complementation analyses. It encodes a CC-NBS-LRR disease resistance protein, and transient expression assays conducted in the leaves of Nicotiana benthamiana indicate that Ph-2 is predominantly localized within the nucleus. In comparison to its susceptible allele (ph-2), the transient expression of Ph-2 can elicit hypersensitive responses (HR) in N. benthamiana, and subsequent investigations indicate that the structural integrity of the Ph-2 protein is likely a requirement for inducing HR in this species. Furthermore, ethylene and salicylic acid hormonal signaling pathways may mediate the transmission of the Ph-2 resistance signal, with PR1- and HR-related genes potentially involved in the Ph-2-mediated resistance. Our results could provide a theoretical foundation for the molecular breeding of tomato varieties resistant to late blight and offer valuable insights into elucidating the interaction mechanism between tomatoes and P. infestans.

Parthenocarpy and male sterility are highly desirable traits in tomato breeding and molecular study. The stamen carpelloid mutant generally displays male sterility. A natural mutant displaying carpelloid stamen and parthenocarpy (csp) was identified in our research group. In this study, the csp locus was finely mapped to a 65 kb interval, which contained six putative genes. One of them, Solyc04g081000, encodes the tomato class B MADS box gene TAP3 (syn. SlDEF). Sequencing data revealed that a copia long terminal repeat retrotransposon was inserted in the first intron of the TAP3 gene of the csp mutant. qRT-PCR showed that the expression of TAP3 was significantly down-regulated in the petals and stamens of the csp mutant. A phenotypic analysis of the TAP3 gene-edited mutants and allelism tests indicated that TAP3 was the gene underlying csp, and csp was a novel allelic mutation of TAP3. The results of this study will lay the foundation for a further analysis of the function of TAP3 and provide materials and a basis for a further study of the functional differentiation of tomato B-class genes.

Male sterility is an essential trait for minimizing costs and ensuring seed purity in the production of tomato hybrid seeds. However, its application in commercial breeding faces challenges such as instability, low stigma exsertion rates, and the lack of molecular markers to facilitate the efficient backcrossing of male sterile loci into elite tomato lines. This study characterized the male sterile-24 (ms-24) mutant, which demonstrated exserted stigmas and complete male sterility. Our histological examination revealed that ms-24 anthers displayed dysfunctional development of the tetrads and tapetum. The ms-24 locus was finely mapped to a 149 kb interval containing 22 putative genes. Among these, Solyc02g079810, also known as MS-10, encodes a basic helix–loop–helix (bHLH) transcription factor essential for tapetum and pollen development. A sequencing analysis revealed an approximately 4.9 kb retrotransposon insertion in the first exon of the MS-10 gene in ms-24. Allelism tests confirmed that ms-24 was allelic to ms-10, which is also allelic to ms-35 and ms-36. The same retrotransposon insertion was also identified in the ms-10 mutant, and a similar insertion of retrotransposon was detected in the second exon of the MS-10 gene in the ms-36 mutant. Based on these retrotransposon sequences, codominant insertion–deletion (InDel) markers, MS-24I and MS-35I, were developed for the precise identification of the ms-24, ms-10, ms-35, and ms-36 alleles. These findings establish a foundational basis for subsequent investigations into the molecular mechanisms underlying male sterility and enhance the selection process of male sterile lines in tomato hybrid breeding programs.

The root parasitic weed Phelipanche aegyptiaca (Pers.) Pomel poses a serious threat to solanaceous crops, leading to yield losses of up to 80% in tomato (Solanum lycopersicum L.). Strigolactones (SLs), derived from the carotenoid metabolic pathway, serve as key host-recognition signals for root-parasitic plants. This study investigated the molecular mechanisms of host resistance, focusing on the suppression of SL biosynthesis through altered carotenoid metabolism in the high-pigment tomato mutants hp-1 and og^c. Both pot experiment and in vitro seed germination assays demonstrated that the mutants exhibited reduced susceptibility to P. aegyptiaca and triggered lower germination rates in broomrape seeds compared to the wild-type cultivar AC. Quantitative RT-PCR analysis revealed a significant downregulation of SL biosynthesis genes (SlD27, SlCCD7, SlCCD8, SlMAX1, SlP450, SlDI4) in hp-1 at various parasitic stages post-inoculation, with a more pronounced suppression observed in hp-1 than in og^c. Notably, the extent of downregulation correlated with the enhanced resistance phenotype in hp-1. These findings highlight a synergistic resistance mechanism involving the coordinated regulation of carotenoid metabolism and SL biosynthesis, providing new insights into the molecular defense network underlying tomato-broomrape interactions.

Tomato fruit firmness is a critical determinant of postharvest quality, dictating storage, ultimate shelf-life, and market value. While previous research on tomato fruit firmness has largely confined to wild or heirloom accessions, the genetic basis underlying this trait in modern elite breeding lines remains largely unexplored. In this study, we dissect the genetic architecture of fruit firmness using a recombinant inbred line (RIL) population derived from a cross between the modern inbred line CF-1 and the conventional cultivar Moneymaker. Quantitative trait locus (QTL) mapping revealed three firmness-associated loci on chromosomes 3, 4, and 5. The major-effect QTL qFF3.1 on chromosome 3 accounted for 11.55% of the phenotypic variation and was further confirmed by bulked segregant analysis (BSA-seq). Fine-mapping in the F _2:3 population delimited qFF3.1 to a 111 kb interval containing 26 predicted gene models. Combined analysis of functional annotations and RNA-seq data from near-isogenic lines (NILs), we prioritized six candidate genes associated with cell wall development and ethylene responsive, and four of which exhibiting differential expression patterns across fruit ripening stages. To our knowledge, qFF3.1 is the first major-effect QTL for fruit firmness identified in a modern tomato breeding line. Our findings offer molecular insights into the regulation of fruit firmness, and provide a strategy for improving shelf-life and other postharvest traits.