SUMMARY The assembly and scaffolding of plant crop genomes facilitate the characterization of genetically diverse cultivated and wild germplasm. The cultivated tomato (Solanum lycopersicum) has been improved through the introgression of genetic material from related wild species, including resistance to pandemic strains of tobacco mosaic virus (TMV) from Solanum peruvianum. Here we applied PacBio HiFi and ONT Nanopore sequencing to develop independent, highly contiguous and complementary assemblies of an inbred TMV‐resistant tomato variety. We show specific examples of how HiFi and ONT datasets can complement one another to improve assembly contiguity. We merged the HiFi and ONT assemblies to generate a long‐read‐only assembly where all 12 chromosomes were represented as 12 contiguous sequences (N50 = 68.5 Mbp). This chromosome scale assembly did not require scaffolding using an orthogonal data type. The merged assembly was validated by chromosome conformation capture data and is highly consistent with previous tomato genome assemblies that made use of genetic maps and Hi‐C for scaffolding. Our long‐read‐only assembly reveals that a complex series of structural variants linked to the TMV resistance gene likely contributed to linkage drag of a 64.1‐Mbp region of the S. peruvianum genome during tomato breeding. Through marker studies and ONT‐based comprehensive haplotyping we show that this minimal introgression region is present in six cultivated tomato hybrid varieties developed in three commercial breeding programs. Our results suggest that complementary long read technologies can facilitate the rapid generation of near‐complete genome sequences.

Meiosis is a key feature of sexual reproduction. During meiosis homologous chromosomes replicate, recombine and randomly segregate, followed by the segregation of sister chromatids to produce haploid cells. The unique genotypes of recombinant gametes are an essential substrate for the selection of superior genotypes in natural populations and plant breeding. In this review we summarize knowledge on meiosis in diverse monocot and dicot crop species and provide a thorough resource of cloned meiotic mutants in six crop species (rice, maize, wheat, barley, tomato and brassicas). Generally, the functional roles of meiotic proteins are conserved between plant species, but we highlight notable differences in mutant phenotypes. The physical lengths of plant chromosomes vary greatly, for instance wheat chromosomes are roughly one order of magnitude longer than those of rice. We explore how chromosomal distributions of crossover recombination can vary between species. We conclude that research on meiosis in crops will continue to complement that in Arabidopsis, and alongside possible applications in plant breeding will facilitate a better understanding of how the different stages of meiosis are controlled in plant species.

Various phenolic and flavonoid compounds that are secondary plant metabolites are known to contribute to physiological wellbeing. Extraction efficiency of such compounds from plant sources is dependent on the extraction solvent type and composition, and its pH. In this study, different extraction variables were examined: heating time (20 to 180 min), temperature (60˚C, 75˚C and 90˚C) and pH (2.5, 3.0, 4.0, 5.0, 6.0 and 7.0). Hot water was used in the extraction of dry samples. For phenolics, the most efficient extraction was by using water at 60˚C for 180 min, whereby 5.95 mg GA equivalent/dry extract was achieved. The most efficient extraction of flavonoids was achieved with water at 60˚C for 150 min, whereby 43 µg Quercetin equivalent/dry extract was obtained. Adjusting the solvent to pH 2.5 increased the yield to 45.3 µg Quercetin equivalent/dry extract.

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Curcuma aeruginosa or temu hitam is herbaceous plant with high therapeutic values in its rhizome that is widely used in traditional medicine. However, molecular studies on the secondary metabolite biosynthetic pathway of C. aeruginosa is still limited. Hence, the aim of this study was to explore and reconstruct the secondary metabolite biosynthetic pathway of C. aeruginosa rhizome by integrating the metabolite profiling and transcriptomic data. A total of 81 metabolites were identified in the rhizome of C. aeruginosa; amongst others are curzerene and β-Cubebene which are potent antioxidants. A total of 28,225 unigene were obtained from the transcriptomic sequencing of C. aeruginosa rhizome and analysed to identify potential genes associated with the biosynthesis of its metabolites. Of these, 43 unigenes were identified and mapped onto five sub-pathways; i.e. carotenoid biosynthetic pathway, diterpenoid biosynthetic pathway, monoterpenoid biosynthetic pathway, terpenoid and steroid biosynthetic pathway, and sesquiterpenoid and triterpenoid biosynthetic pathway. This study demonstrated a systematic bioinformatic approach to reconstruct a metabolic pathway in the rhizome of C. aeruginosa using bioinformatic approach.