Functional gametophytic self-incompatibility in a peripheral population of Solanum peruvianum (Solanaceae)

Abstract

The transition from self-incompatibility to self-compatibility is a common transition in angiosperms often reported in populations at the edge of species range limits. Geographically distinct populations of wild tomato species (Solanum section Lycopersicon (Solanaceae)) have been described as polymorphic for mating system with both self-incompatible and self-compatible populations. Using controlled pollinations and sequencing of the S-RNase mating system gene, we test the compatibility status of a population of S. peruvianum located near its southern range limit. Pollinations among plants of known genotypes revealed strong selfincompatibility; fruit set following compatible pollinations was significantly higher than following incompatible pollinations for all tested individuals. Sequencing of the S-RNase gene in parents and progeny arrays was also as predicted under self-incompatibility. Molecular variation at the S-RNase locus revealed a diverse set of alleles, and heterozygosity in over 500 genotyped individuals. We used controlled crosses to test the specificity of sequences recovered in this study; in all cases, results were consistent with a unique allelic specificity for each tested sequence, including two alleles sharing 92% amino-acid similarity. Site-specific patterns of selection at the S-RNase gene indicate positive selection in regions of the gene associated with allelic specificity determination and purifying selection in previously characterized conserved regions. Further, there is broad convergence between the present and previous studies in specific amino-acid positions inferred to be evolving under positive selection.

Colonization, Baker's law, and the evolution of gynodioecy in Hawaii: implications from a study of Lycium carolinianum

“…Greater S‐RNase allelic diversity was recovered from mainland populations as compared to islands (20 vs. 3 alleles, respectively), and only two heterozygous genotypes were present in Hawaii compared to 18 heterozygous genotypes from the mainland. In addition, models incorporating diversifying selection are a more likely fit for S‐RNases from the mainland, which is consistent with previous studies in Lycium (Savage and Miller, ) and other genera (Igic et al., ; Miller and Kostyun, ) with functional gametophytic self‐incompatibility. Long‐distance dispersal followed by establishment on oceanic islands is thought to be relatively rare; thus, one might expect a genetic bottleneck at the S‐RNase locus (e.g., Miller et al., ; Nowak et al., ; Pannell, ).…”

“…Once alleles were designated, individual plants were assigned genotypes. Previous studies in self‐incompatible populations have demonstrated that models incorporating positive selection fit S‐RNase allelic data significantly better than corresponding models that do not incorporate positive selection (Savage and Miller, ; Igic et al., ; Miller et al., ; Miller and Kostyun, ). Following these studies, we used the codeml package in PAML (Yang, ) as implemented in PAMLX (Xu and Yang, ) to assess whether the pattern of selection on S‐RNase was consistent with results from our controlled crosses and previous studies documenting self‐incompatibility.…”

Overcoming Self-Incompatibility in Diploid Potato Using CRISPR-Cas9

“…This process, known as pseudo-self-incompatibility, has also been reported in grasses in which artificial self-pollination techniques can contribute to SI breakdown (Do Canto et al, 2016). Similarly, sporadic fruit set has been observed across Solanaceae species such as Witheringia solanacea , S. carolinense , S. peruvianum , and N. alata in which floral age, flowering stage, and delayed floral abscission has been associated with fruit set in SI populations (Stone et al, 2006; Mena-Ali and Stephenson, 2007; Miller and Kostyun, 2011; Liao et al, 2016). This phenomenon has also been observed in species under sporophytic SI, in which floral age reduces the expression of the S -locus associated genes in Brassica oleracea resulting in SI breakdown (Hadj-Arab et al, 2010).…”

Characterisation of the tolerance to the beet leafhopper transmitted virescence agent phytoplasma in the PI128655 accession of Solanum peruvianum

“…Crosses of S. peruvianum were performed as described in Miller & Kostyun () in an insect‐proof greenhouse. Briefly, pollen was collected from individual parental flowers by vortexing them in a microtube, and then applied onto the stigmas of flowers of the maternal parent.…”