Self-incompatibility of Zinnia angustifolia HBK (compositae)

Abstract

Visible light and UV epifluorescence microscopy were used to assess self-incompatibility (SI) in Zinnia angustifolia clones. Pistils were fixed 24 h after pollination and stained either with aniline blue in lactophenol (visible light microscopy) or decolorized aniline blue (fluorescence microscopy). Percentage of florets with embryos 21 days following pollination (% embryo set) was used as a control. Embryo set following self-or incompatible cross-pollinations ranged from 0~ to 9.9%, whereas compatible crosses yielded 55.5%-87.1% embryo set. Observations using visible light microscopy indicated pollen load and number of germinated grains were significantly higher for compatible compared to incompatible crosses, and both variables were positively correlated (r= 0189-0.96) to 0/0 embryo set. Examinations with UV epifluorescence microscopy revealed pollen load was higher and little or no callose accumulated in stigmatic papillae following compatible crosses, whereas for incompatible crosses, pollen load was low and callose lenticules were deposited in stigmatic papillae; the correlation between pollen load and 0/0 embryo set was 0.89. The intensity of callose fluorescence of the pollen tube-papillae attachment sites was quantitatively measured via microspectrofluorometry. Callose fluorescence intensity ranged from 47.9% to 62.6% for incompatible and from 6.4% to 9.9~ for compatible crosses, and was negatively correlated (r= -0.95) with 0/0 embryo set. Microscopal techniques permit rapid assessment of SI and may be used routinely when each observed or measured parameter is highly correlated to the incompatibility response.

Mate Availability and Fecundity Selection in Multi-Allelic Self-Incompatibility Systems in Plants

“…In the SSIcod model, the alleles act codominantly in both pollen and style, in the SSIdom model, alleles have an identical dominance hierarchy in both pollen and style, and for SSIdomcod, the alleles act in a dominance hierarchy in the pollen and codominantly in the style. These models were chosen to represent the variation found in SSI systems: codominance in both pollen and style is reported in Caryophyllaceae (Lundquist 1994), codominance in the style and dominance hierarchy in the pollen is described in Brassicaceae (Ockendon 1974;Stevens and Kay 1989), and dominance hierarchy in pollen and style is found in Asteraceae (Samaha and Boyle 1989) and Convolvulaceae (Kowyama et al 1994). Here, we consider equilibrium patterns of mate availability under the same four models of SI in an attempt to describe the expected limitations in mate availability in natural populations.…”