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.

Storage roots are an ecologically and agriculturally important plant trait that have evolved numerous times in angiosperms. Storage roots primarily function to store carbohydrates underground as reserves for perennial species. In morning glories, storage roots are well characterized in the crop species sweetpotato, where starch accumulates in storage roots. This starch-storage tissue proliferates, and roots thicken to accommodate the additional tissue. In morning glories, storage roots have evolved numerous times. The primary goal of this study is to understand whether this was through parallel evolution, where species use a common genetic mechanism to achieve storage root formation, or through convergent evolution, where storage roots in distantly related species are formed using a different set of genes. Pairs of species where one forms storage roots and the other does not were sampled from two tribes in the morning glory family, the Ipomoeeae and Merremieae. Root anatomy in storage roots and fine roots was examined. Furthermore, we sequenced total mRNA from storage roots and fine roots in these species and analyzed differential gene expression. Anatomical results reveal that storage roots of species in the Ipomoeeae tribe, such as sweetpotato, accumulate starch similar to species in the Merremieae tribe but differ in vascular tissue organization. In both storage root forming species, more genes were found to be upregulated in storage roots compared to fine roots. Further, we find that fifty-seven orthologous genes were differentially expressed between storage roots and fine roots in both storage root forming species. These genes are primarily involved in starch biosynthesis, regulation of starch biosynthesis, and transcription factor activity. Taken together, these results demonstrate that storage roots of species from both morning glory tribes are anatomically different but utilize a common core set of genes in storage root formation. This is consistent with a pattern of parallel evolution, thus highlighting the importance of examining anatomy together with gene expression to understand the evolutionary origins of ecologically and economically important plant traits.

Mature fruit of 330 accessions of Capsicum chinense Jacq. from the USDA/ARS Capsicum germplasm collection were characterized for fruit length, width, weight, and color. Mean fruit length was determined to be 47 mm with a range from 7.9 mm to 113.7 mm. Mean fruit width was 21.17 mm with a range of 6.18 mm to 40.0 mm. Mean fruit weight was 6.31 g with a range of 0.18 g to 22.7 g. Distributions of all characteristics were positively skewed. Distributions of fruit length, fruit weight, and fruit length/width failed the Kolmogorov-Smirnov test for normality. The distribution for fruit width was normal. Ninety-two percent of the accessions examined were elongate. Mature fruit colors included red, orange, yellow, brown (chocolate), and cream. The germplasm collection contained primarily pendent larger-fruited cultivated forms of the species, but also contained upright small-fruited primitive and semipendent transitional forms. These data define the variability for mature fruit characteristics within this germplasm collection and provide a baseline against which future introductions/acquisitions can be compared. Additional sampling of the gene pool might be expected to substantially enhance the genetic variability within the primitive forms of this species.