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

Abstract

Polyploidization is common among angiosperms and might induce typically allogamous plants to become autogamous (self-compatible, relying on sexual self-fertilization) or apomictic (achieving asexual reproduction through seeds). This work aimed to determine whether neopolyploidy leads to the breakdown of the self-incompatibility system in the hexaploid non-apomictic species Handroanthus serratifolius (Vahl) S. Grose, through analyses of its floral biology, pollination biology and breeding system. Although anthesis lasted for three days, increasing the overall floral display, receptivity decreased as of the second day. Centridini and Euglossini bees were the main pollinators, and low nectar availability (1.95 ± 1.91 μl/flower) might have obliged them to visit multiple flowers. We observed low reproductive efficacy. That might be explained by self-sterility and by the great number of flowers per individual, which could increase the frequency of geitonogamy. Ovule penetration by the pollen tubes in self-pollinated pistils with posterior abscission indicated late-acting self-incompatibility in H. serratifolius, as observed in other diploid Bignoniaceae species, although inbreeding depression cannot be excluded. The self-sterility found in the monoembryonic, hexaploid individuals studied here contrasts with the results for other neopolyploid Handroanthus and Anemopaegma species, which are often autogamous and apomictic. Our results suggest that neopolyploidy is not the main factor leading to self-fertility in Handroanthus.Key words: apomixis, late-acting self-incompatibility, monoembryony, polyploidy, Tabebuia serratifolia Acta Botanica Brasilica 27(4): 714-722. 2013. Self-sterility in the hexaploid Handroanthus serratifolius(Bignoniaceae), the national flower of Brazil

Sporophytic apomixis in polyembryonic Handroanthus serratifolius (Vahl) S.O. Grose (Bignoniaceae) characterizes the species as an agamic polyploid complex

“…The diploid Bignoniaceae show a predominance of 2n = 40 chromosomes (Goldblatt and Gentry 1979;Gentry 1980), and most of them present late-acting self-incompatibility-LSI Bianchi 1993, 1999;Bittencourt et al 2003;Bittencourt and Semir 2005;Gandolphi and Bittencourt 2010). Neopolyploidy has been observed in species of Anemopaegma, Dolichandra, Pyrostegia and Handroanthus, with records of 2n = 60, 80 and 120 chromosomes (Goldblatt and Gentry 1979;Piazzano 1998;Firetti-Leggieri et al 2011;Alves et al 2013;Sampaio et al 2013b). Most neopolyploid species of this family are self-fertile, although there are no evidences that neopolyploidy per se is the primary cause of self-fertility in these species.…”

“…Among the seven neopolyploid species studied for their breeding systems, six are reported as self-fertile (Gobatto-Rodrigues and Stort 1992;Bittencourt and Moraes 2010;Firetti-Leggieri et al 2013;Sampaio et al 2013a), with the exception of H. serratifolius (Vahl) S.O. Grose that is self-sterile (Alves et al 2013).…”

“…Handroanthus serratifolius is taxonomically closely related to Handroanthus ochraceus and H. chrysotrichus and widely distributed in the Neotropics (Gentry 1992;Grose and Olmstead 2007). They are hexaploid (2n = 120 chromosomes) trees, with self-sterile and monoembryonic populations (Alves et al 2013), but also with polyembryonic populations with unknown breeding system (Mendes-Rodrigues et al 2012). Monoembryonic populations of H. serratifolius occur in Minas Gerais State (Sampaio 2010;Alves et al 2013) and polyembryonic populations have been observed both in Goiás and Minas Gerais states, in Southeastern Brazil (Mendes-Rodrigues et al 2012).…”

Reproductive systems and low outbreeding barriers between Jacaranda cuspidifolia and J. mimosifolia (Jacarandeae, Bignoniaceae)

“…Fruit set data from experimental pollinations in J. cuspidifolia indicated complete self-sterility (no fruit initiated from flowers tested for spontaneous (automatic) and induced (manual) self-pollination in six individuals). Despite the high ovule-seed conversion efficiency of compatible pollinations (including open pollination) in J. cuspidifolia, fruit set by natural pollination was remarkably lower than in cross-pollination in both species which implies their low reproductive efficacy, a common feature in most self-sterile species of Jancaranda (Vieira et al 1992, Guimarães et al 2008, Maués et al 2008, Milet-Pinheiro et al 2008, Sampaio 2010) and other Bignoniaceae (Bittencourt et al 2003, 2011, Bittencourt and Semir 2004, 2005, Gandolphi and Bittencourt 2010, Sampaio 2010, Alves et al 2013, Sampaio et al 2016) that may be related to pollen limitation and ovule discounting (Barrett 2002).…”

Um, dois, três, quatro! Um estudo de caso de poliembrionia em Handroanthusserratifolius (Vahl) S. Grose, (Bignoniaceae), Maranhão, Brasil

“…Handroanthus serratifolius é uma árvore com 30-37m de altura; sua flor demonstra uma corola tubular infundibuliforme de coloração amarela; o fruto é uma cápsula linear, com muitos nectários extraflorais com a presença de várias sementes retangulares aladas, com germinação simples (GENTRY, 1992;ALVES et al, 2013). Para obtenção das sementes foram coletados frutos maduros e secos de H. serratifolius, na estação reprodutiva da espécie que compreende setembro a dezembro.…”