Lycoris species of the Amaryllidaceae are important ornamental and medicinal plants in Asia. Karyotypes of Lycoris species have been studied extensively since the time when their chromosome numbers were first counted over 80 years ago. Based on karyotype, Lycoris taxa can be classified into the monomorphic A group, dimorphic MT group, and the sterile dikaryotype MT-A group. Numerous reports dealing with karyotype analysis and phylogenetic relationship in the genus Lycoris have been published. However, there are disputes and controversies regarding karyotype evolution resulting from lacking efficient and reliable markers for chromosome identification in the genus Lycoris. In this study, we applied fluorescent in situ hybridization (FISH) to visualize the 5S and 45S rDNA loci on chromosomes as landmarks for chromosome identification in Lycoris taxa. In total, 12 accessions of three karyotype groups, including nine species and three artificial dikaryotype hybrids, were investigated. A high degree of variation in the number and position of 5S and 45S rDNA loci was detected among Lycoris taxa. There were four to 14 FISH signals of 5S rDNAs and two to 12 FISH signals of 45S rDNAs observed in each investigated Lycoris accession. Lycoris accessions with the same karyotype 2n = 22A may have different numbers of rDNA loci, which distributed at different chromosomal positions. In an interspecific hybrid, the number and chromosomal position of both 5S and 45S rDNA loci were either the combinations of those in their parental species or considerably modified. Overlapping FISH signals of 5S and 45S rDNAs were colocalized with a 4′, 6-diamidino-2-phenylindole-positive band at the end of the p-arm on almost every T-type chromosome (but not the A-type chromosomes). Based on the features of T-type chromosomes, the possibility of centromeric fission in karyotypic evolution of Lycoris is discussed.
Pepper (Capsicum L.) is a major vegetable and spice crop worldwide. Global production of both fresh and dried fruit continues to increase steadily in terms of area harvested and yield. Various topics are addressed in this review, including recent additions to and clarification of Capsicum taxonomy, genetic resources of Capsicum, cytogenetic studies, the current status of our understanding of the mechanisms affecting the biosynthesis of capsaicinoids, the use of gene mutations to elucidate carotenoid biosynthetic pathways and their regulation, and recent advances in whole-genome sequencing and assembly.