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Summary: In vivo haploid induction has been extended from maize to monocotyledonous plants like rice, wheat, millet and dicotyledonous plants such as tomato, rapeseed, tobacco and cabbage. Accurate identification of haploids is a crucial step of doubled haploid technology, where a useful identification marker is very pivotal. R1‐nj is an extensively used visual marker for haploid identification in maize. RFP and eGFP have been shown to be feasible in identifying haploid. However, these methods are either limited to specific species, or require specific equipment. It still lacks an efficient visual marker that is practical across different crop species. In this study, we introduced the RUBY reporter, a betalain biosynthesis system, into maize and tomato haploid inducers as a new marker for haploid identification. Results showed that expression of RUBY could result in deep betalain pigmentation in maize embryos as early as 10 days after pollination, and enabled 100% accuracy of immature haploid embryo identification. Further investigation in tomato revealed that the new marker led to deep red pigmentation in radicles and haploids can be identified easily and accurately. The results demonstrated that the RUBY reporter is a background‐independent and efficient marker for haploid identification and would be promising in doubled haploid breeding across different crop species. [ABSTRACT FROM AUTHOR]

SUMMARY: In higher plants, the generation and release of viable pollen from anthers is vital for double fertilization and the initiation of seed development. Thus, the characterization of genes related to pollen development and anther dehiscence in plants is of great significance. The F‐box protein COI1 plays a crucial role in the jasmonate (JA) signaling pathway and interacts with many JAZ family proteins in the presence of jasmonoyl‐isoleucine (JA‐Ile) or coronatine (COR). The mutation of AtCOI1 in Arabidopsis leads to defective anther dehiscence and male sterility (MS), although COI has not been shown to affect fertility in Zea mays (maize). Here we identified two genes, ZmCOI2a and ZmCOI2b, that redundantly regulate gametophytic male fertility. Both ZmCOI2a and ZmCOI2b are highly homologous and constitutively expressed in all tissues tested. Subcellular localization revealed that ZmCOI2a and ZmCOI2b were located in the nucleus. The coi2a coi2b double mutant, generated by CRISPR/Cas9, had non‐dehiscent anthers, delayed anther development and MS. In addition, coi2a coi2b male gametes could not be transmitted to the next generation because of severe defects in pollen germination. The JA content of coi2a coi2b anthers was unaltered compared with those of the wild type, and the exogenous application of JA could not rescue the fertility defects of coi2a coi2b. Transcriptome analysis showed that the expression of genes involving the JA signaling transduction pathway, including ZmJAZ3, ZmJAZ4, ZmJAZ5 and ZmJAZ15, was affected in coi2a coi2b. However, yeast two‐hybrid assays showed that ZmJAZs interacted with ZmCOI1s, but not with ZmCOI2s. In conclusion, ZmCOI2a and ZmCOI2b redundantly regulate anther dehiscence and gametophytic male fertility in maize. Significance Statement: The F‐box protein COI1 plays a crucial role in the jasmonate signaling pathway. However, the function of COI in maize has remained elusive. Here, we identified two genes, ZmCOI2a and ZmCOI2b, that redundantly regulate anther dehiscence, filament elongation and gametophytic male fertility in maize. [ABSTRACT FROM AUTHOR]

To summarize, we demonstrate that I sldmp i mutants induce I in vivo i maternal haploids in a major dicot crop, tomato, and that identification of haploid embryos is facilitated by the FAST-Red marker. Keywords: tomato; doubled haploid technology; maternal haploid induction; genotype independent EN tomato doubled haploid technology maternal haploid induction genotype independent 250 252 3 01/17/22 20220201 NES 220201 Tomato ( I Solanum lycopersicon i ) is the second largest vegetable crop and the largest fruit crop (Costa and Heuvelink, 2018). Ploidy analysis of 218 putative haploid and 2303 putative diploid seedlings showed that FAST-Red can be used with 100% accuracy for selection of maternal haploids in tomato (Figure 1r). [Extracted from the article]