Self-pollination, style length development and seed set in self-compatible Asteraceae: evidence from Senecio vulgaris L.

Abstract

Background: Variation in style length has been reported in Senecio vulgaris and has been associated with outcrossing rate. Aims: To determine if (i) long styles lack germinated pollen on stigmas left to self-pollinate, (ii) successful self-pollination causes styles to stop elongating and shrink in length and (iii) seed set increases with the amount of pollen deposited on stigmas. Methods: Determined germinated self-pollen on stigmas of long and short styles after auto-self-pollination; scored style length over 48 h in self-pollinated and non-pollinated florets; recorded seed set after placing different amounts of pollen on stigmas.Results: Most long-styled florets had zero or low amounts of germinated pollen on stigmas in contrast to most short-styled florets. Styles initially elongated to the same length in self-pollinated and non-pollinated florets, then shrank in length in self-pollinated florets while continuing to elongate in non-pollinated florets. Seed set increased with number of pollen grains deposited on stigmas. Conclusions: Successful self-pollen deposition and/or germination on stigmas of S. vulgaris are indicated by presence of short styles, whereas the opposite is indicated by presence of long styles in florets left to self-pollinate. Self-pollination causes styles to shrink after initially elongating. Seed set is dependent on the amount of pollen deposited on stigmas.

Flower orientation influences floral temperature, pollinator visits and plant fitness

“…High temperature stress can also affect the timing and development of stamens, in turn altering the synchronicity between stamen and pistil elongation and leading to a shift from selfing to outcrossing in some species (Sakata et al ., 2010; Bishop et al ., 2016; Pan et al ., 2017; Pan et al ., 2018). In addition to this temperature‐dependent mating system plasticity, genetically based changes in floral organ development that facilitate adaptive shifts from selfing to outcrossing have been documented in both Solanum and Asteraceae species (Motten & Stone, 2000; Chen et al ., 2007; Vosters et al ., 2014; Irwin et al ., 2016; Love et al ., 2016). Most studies to date have investigated the effects of high heat stress on anthesis and pollination.…”

Biological Traits and Genetic Relationships Amongst Cultivars of Three Species of Tagetes (Asteraceae)

“…Although the expected heterozygosity has a mean of 0.46, the observed heterozygosity was very low in general, ranging from 0.00 to 0.23. This indicates a high degree of homozygosity, probably due to the various floral mechanisms adapted in Asteraceae to reduce the likelihood of self-pollination within co-sexual flowers [ 44 ]. The PIC (polymorphic information content) value, which assesses the informativeness of the markers in a population, ranged from 0.18 in the marker TE11, which was much lower than the others, to 0.66 in the marker TE59, with a general mean of 0.40.…”

Identifying successful combinations by fertility index in old garden roses and hybrid tea roses crosses

“…Other reasons are considered for the lower crossability rate and seed set. Love et al (2016) reported that the diameter of the stigma affects the success of crossbreeding, and the number of seeds may vary according to the amount of pollen on the stigma, although it has been determined that an increase in the amount of pollen on the stigma improves the fruit set rate and the number of seeds ( Falque et al, 1995 ) while an excessive amount of pollen on the stigma can decrease the number of seeds ( Lankinen, Lindström & D’Hertefeldt, 2018 ). Ogilvie et al (1991) argued that the pollen tube growth barrier could cause decreased seed set.…”