Reproductive compatibility in Capsicum is not necessarily reflected in genetic or phenotypic similarity between species complexes

Abstract

Wild relatives of domesticated Capsicum represent substantial genetic diversity and thus sources of traits of potential interest. Furthermore, the hybridization compatibility between members of Capsicum species complexes remains unresolved. Improving our understanding of the relationship between Capsicum species relatedness and their ability to form hybrids is a highly pertinent issue. Through the development of novel interspecific hybrids in this study, we demonstrate interspecies compatibility is not necessarily reflected in relatedness according to established Capsicum genepool complexes. Based on a phylogeny constructed by genotyping using simple sequence repeat (SSR) markers and with a portion of the waxy locus, and through principal component analysis (PCA) of phenotypic data, we clarify the relationships among wild and domesticated Capsicum species. Together, the phylogeny and hybridization studies provide evidence for the misidentification of a number of species from the World Vegetable Center genebank included in this study. The World Vegetable Center holds the largest collection of Capsicum genetic material globally, therefore this may reflect a wider issue in the misidentification of Capsicum wild relatives. The findings presented here provide insight into an apparent disconnect between compatibility and relatedness in the Capsicum genus, which will be valuable in identifying candidates for future breeding programs.

Growing Environment and Heat Treatment Effects on Intra- and Interspecific Pollination in Chile Pepper (Capsicum spp.)

“…Another factor affecting pollination success rate is prezygotic barriers to fertilization among the different species of Capsicum. The intra-and interspecific pollination success rates of wild and domesticated Capsicum species have been previously studied [16,[24][25][26][27][28][29][30][31][32][33][35][36][37][38]. Under no-heat treatment during the winter season, the cross-pollination success rates were similar to those of Parry et al [16], with higher reciprocal pollination success for accessions from the same species than success rates between species.…”

“…Given that many wild Capsicum species originate from harsh environments, including high temperatures and water-deficit stress [8], it is hypothesized that they could serve as sources of tolerance to abiotic stress [16]. Reddy and Kakani [17] found an accession of the wild species C. chacoense that had intermediate heat tolerance, while accessions from domesticated species were either highly heat tolerant or sensitive.…”

“…However, in contrast to other Solanaceae crops, including tomato [9] and potato (S. tuberosum) [10], introgression breeding using wild species has been neglected in Capsicum [7]. Although the genetic diversity and variation within wild populations of Capsicum have been studied [11][12][13][14][15], phenotypic and genotypic information of wild Capsicum species remains limited [8,16]. Lack of phenotypic characterization is likely the major reason why wild relatives are not widely used for improving the chile pepper crop, followed by pre-or post-zygotic barriers to fertilization and linkage drag [17].…”

“…To use the traits of wild relatives in breeding programs, there is a need to understand the potential of these traits for improving the stress resilience of cultivated chile pepper. Wild relatives have been explored in some breeding programs with a major focus on characterizing phylogeny, genetic relatedness, morphology, and cross-compatibility as a basis for understanding interspecies compatibility and identifying barriers to hybridization, which are essential to the design of introgression breeding programs [16]. However, the direct use of multigenic traits derived from wild Capsicum species, which are morphologically divergent and not adapted to modern production systems, has not been successful.…”

“…Similarly, plant growing environment and laboratory-based pollen heat treatment have not been compared for chile pepper. Furthermore, it is known that the cross-compatibility among wild and domesticated Capsicum accessions has yet to be resolved [16]. Therefore, the objectives of this study were to (i) validate the utility of in vitro heat stress pollen characterization through in vivo cross-and self-pollination among heattolerant Capsicum accessions during high temperature and optimal growing seasons and (ii) to evaluate the cross-compatibility among wild and domesticated species to initiate introgression population development, with the overall aim of supporting future research by plant breeders in this important area.…”