Mating in the pseudogamic apomicticAnemopaegma acutifoliumDC: another case of pseudo‐self‐compatibility inBignoniaceae?

Abstract

Self-compatibility in apomictic pseudogamic species is considered fundamental to assure reproduction by seeds in extreme situations, making apomictic species more advantageous than sexual ones in these scenarios. Anemopaegma acutifolium is a polyploidy, apomictic sporophytic species with no endosperm development in ovules of unpollinated pistils, which indicates obligate pseudogamy. Thus, the aim of the present work is to study the breeding system and post-pollination events to test if there is similar pseudogamous development irrespective of pollination treatment. We analysed fruit and seed set obtained in controlled experimental pollinations, as well as embryo number per seed, and the progress of ovule penetration, fertilisation and early endosperm development between self- and cross-pollinated pistils. We found that the species is self-fertile and that spontaneous selfing fruit set is also possible, although emasculated flowers never form fruits. Selfed pistils were as efficient as crossed ones for all parameters analysed, except for a delay in endosperm development observed in the former that may be an effect of the late-acting self-incompatibility. Therefore, the avoidance of selfed pistil abortion seems to be promoted by the presence of adventitious embryos and a normal endosperm. We conclude that A. acutifolium shows apomixis-related pseudo-self-compatibility, as in other self-fertile apomictic species of Bignoniaceae, which confer reproductive assurance and increases fruit-set and persistence ability in fast-changing tropical habitats.

Self-sterility in the hexaploid Handroanthus serratifolius (Bignoniaceae), the national flower of Brazil

“…If we consider the self-compatible neopolyploid species of Bignoniaceae as presenting strong inbreeding depression, the similar fruit-set between self-and cross-pollinations in apomictic plants (Bittencourt & Semir 2005;Bittencourt & Moraes 2010;Firetti-Leggieri et al 2013;Sampaio et al 2013a) would be justified only by the development of adventitious embryos, and we would have to assume that inbreeding depression does not affect endosperm development, which is unlikely. Histological studies of post-pollination events of apomictic self-compatible neopolyploid species of Bignoniaceae do not show endosperm malformations that could be caused by inbreeding depression (Bittencourt & Moraes 2010;Sampaio et al 2013a), although a slight delay in endosperm development, which is commonly associated with the action of the LSI, has been reported in Anemopaegma acutifolium (Sampaio et al 2013a). In addition, inbreeding depression is not expected to occur in neopolyploids such as H. serratifolius, especially allopolyploids, which can avoid inbreeding problems due to high rates of heterozygosity (Barringer 2007, Husband et al 2008.…”

“…Eighty percent of the studied species present self-sterility, which is often characterized as a result of late-acting self-incompatibility (LSI) mechanisms (Gibbs & Bianchi 1993;Bittencourt et al 2003;Bittencourt & Semir 2005;Gandolphi & Bittencourt 2010). To date, all neopolyploid Bignoniaceae species have been found to be self-compatible (Gobatto-Rodrigues & Stort 1992;Bittencourt & Semir 2005;Bittencourt & Moraes 2010;Firetti-Leggieri et al 2013;Sampaio et al 2013a), although not all self-compatible species are neopolyploids (Dutra & Machado 2001;Yanagizawa & Maimoni-Rodella 2007;Qu et al 2007). Therefore, self-fertility in Bignoniaceae could be caused by various factors, of which polyploidy appears to be one of the most important.…”

“…Studies of the breeding systems of the neopolyploid species of Anemopaegma and Handroanthus have shown self-fertility and polyembryony (Bittencourt & Semir 2005;Bittencourt & Moraes 2010;Mendes-Rodrigues et al 2012;Firetti-Leggieri et al 2013;Sampaio et al 2013a). Histological analyses have shown that the supernumerary embryos found in polyembryonic seeds arise from somatic tissues of the ovule in Handroanthus ochraceus (Cham.)…”

“…Although neopolyploidy seems to be effectively associated with the breakdown of self-incompatibility systems, especially the gametophytic system (de Nettancourt 1977;Richards 1986;Levin 2002;Pannell et al 2004;Barringer 2007), some studies suggest that the self-fertility found in these pseudogamic apomictic sporophytic species is not determined exclusively by neopolyploidy (Oliveira et al 1992;Bittencourt & Semir 2005;Bittencourt & Moraes 2010;Sampaio et al 2013a). The LSI found in most species of Bignoniaceae allows pollen tube growth, ovule penetration, fertilization and endosperm development prior to self-pollinated pistil abscission (Bittencourt et al 2003;Bittencourt & Semir 2005;Gandolphi & Bittencourt 2010).…”

“…In apomictic species, adventitious embryos develop irrespective of pollination but are able to reach maturity only when the endosperm is available (Bittencourt & Moraes 2010;Sampaio et al 2013b). Therefore, the presence of adventitious embryos in self-fertilized ovules with endosperm development, which is common in LSI species, could trigger the fruit-set of self-pollinated pistils (Oliveira et al 1992;Bittencourt & Moraes 2010;Sampaio et al 2013a).…”