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strong. One reason for trait variability in seed-produced cultivars could be the inbreeding barriers that exist in Echinacea germplasm ( Ault, 2006 ). Although poorly understood in Echinacea , one such barrier is assumed to be self-incompatibility (SI

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Cultivars of the Japanese pear [Pyrus pyrifolia (Burm.) Nakai] have variable degrees of self-incompatibility (SI) and can be classified into at least three groups: strong, intermediate, or weak SI; as shown by the extent of self-pollen tube growth in the style, and the percentage of fruit set following self-pollination. Following self-pollination, the elongation of pollen tubes in the detached styles of `Kosui' and `Kikusui' became increasingly suppressed from 4 days before anthesis (–4 DAA) to 2 days after anthesis (2 DAA). Tube growth of `Kosui' was more suppressed than that of `Kikusui' during this period. In `Osa-Nijisseiki', however, the rate of tube growth did not vary with stage of stylar development, from –8 to 2 DAA. Pollen tubes elongated much better after cross-pollination than after self-pollination at all stages tested, and the extent of the elongation increased as the styles matured. The concentration of total S-protein (sum of two S-proteins per buffer-soluble protein) increased with stylar development, but the rate of increase varied with the cultivar. The rate was significantly greater in the strongly self-incompatible `Kosui' than in the moderately self-incompatible `Kikusui', and was slowest in the weakly self-incompatible `Osa-Nijisseiki' at all developmental stages. During stylar maturation, the concentration of S4-protein, which is common in all cultivars, was highest in `Kosui', followed by `Kikusui' and `Osa-Nijisseiki'. Thus, the cultivar differences in SI expression in the Japanese pear are determined about –4 DAA and appear to be regulated, in part, by the concentration of S-proteins produced in the style.

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adequate cropping ( Waite, 1894 ). Self-fertilization in pear is prevented by a gametophytic self-incompatibility system ( de Nettancourt, 2001 ) and pear cultivars are generally considered self-incompatible ( Crane and Lewis, 1942 ; Sanzol and Herrero

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-sterility mainly occurs as a result of self-incompatibility (SI) and EID ( Sage et al., 2006 ). Three types of SI occur in flowering plants: homomorphic sporophytic SI, homomorphic gametophytic SI, and heteromorphic SI ( Gibbs, 2014 ). In sporophytic SI, the

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Low seed set has been reported following self-pollinations of flowering dogwood (Cornus florida L.). The objective of this study was to verify the presence of self-incompatibility in C. florida. `Cherokee Princess' stigmas and styles were collected 1, 2, 4, 8, 12, 24, 48, and 72 hours after cross- and self-pollinations, stained with aniline blue and observed using a fluorescence microscope. Pollen germinated freely following self-pollinations, but self-pollen tubes grew slower than those resulting from cross-pollinations. By 48 hours after cross-pollination, pollen tubes had reached the bottom of the style while pollen tubes in self-pollinated flowers had only penetrated the upper third of the style. Evidence of reduced pollen tube growth rate in self-pollinations of `Cherokee Chief' and `Cherokee Brave' was also obtained. This study provides evidence of a gametophytic self-incompatibity system in C. florida. It was also determined that stigmas of C. florida `Cherokee Princess' are receptive to pollen from 1 day prior to anthesis to 1 day after anthesis.

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( Vaccinium angustifolium ), and hexaploid rabbiteye blueberry [ Vaccinium ashei ( Rowland et al., 2012 )]. Most cultivars are self-incompatible ( Chavez and Lyrene, 2009 ; Ehlenfeldt and Kramer, 2012 ; Miller et al., 2011 ; Yang et al., 2017 ). Self-incompatibility

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Self-incompatibility is a genetic mechanism that exists in flowering plants to prevent a plant from being pollinated by its own pollen and to promote cross-pollination. Gametophytic SI (GSI), one form of SI, has been extensively studied and S

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Seven self-incompatibility (S) alleles (S2, S13, S15, S18, S24, S39 , and S51 ) were identified in various hybrids and breeding lines of broccoli [Brassica oleracea L. (Botrytis group)]. The international S. allele collection of Brassica oleracea at the National Vegetable Research Station was used to assure standardized identification.

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Self-incompatibility in angiosperms is known as a mechanism for preventing self-fertilization and promoting outcross pollination by arresting pollen tube growth. One of the SI systems, RNase-mediated gametophytic SI (GSI), is based on the

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Self-incompatibility was investigated in sour cherry (Prunus cerasus L.) by examining pollen growth in the pistil by use of ultraviolet fluorescence microscopy following self- and cross-pollination. The sour cherry cultivars Tschernokorka and Crisana exhibit pollen tube inhibition in the style characteristic of gametophytic self-incompatibility. `Meteor' and `Montmorency' appear to be partially self-incompatible, with few self-pollen tubes reaching the ovary. Several hybrid seedlings from crosses between self-compatible cultivars were self-incompatible, suggesting that these self-compatible parental cultivars carry self-incompatibility alleles.

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